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Ube IRitral Science Series

Edited by L. H. BAILEY

THE POTATO

Efte iaural Science Scricg

Edited by L. H. Bailey

The Soil. King.

The Spraying of Plants. Lodeman.

Milk AND ITS Products. Wing. Enlarged and Revised.

The Fertility of the Land. Boherts.

The Principles of Fruit-growing. Bailey. 20th

Edition, Bevised.
Bush-fruits. Card. Bevised.
Fertilizers. Voorhees. Bevised.
The Principles of Agriculture. Bailey. Bevised.
Irrigation and Drainage. King.
The Farmstead. Boherts.
Rural Wealth and Welfare. Fairchild.
The Principles of Vegetable-gardening. Bailey.
Farm Poultry. Watson. Enlarged and Bevised.
The Feeding of Animals. Jordan. (Now Eviral

Text-Book. )
The Farmer's Business Handbook. Boberts.
The Diseases of Animals. Mayo.
The Horse. Boberts.
How TO Choose a Farm. Hunt.
Forage Crops. Voorhees.

Bacteria in Relation to Country Life. Lipman.
The Nursery-book. Bailey.
Plant-breeding. Bailey and Gilbert. Bevised.
The Forcing-book. Bailey.

The Pruning-book. Bailey. (Now Rural Manual Series.)
Fruit-growing in Arid Regions. Paddock and Whipple.
Rural Hygiene. Ogden.
Dry-farming. Widtsoe.
Law for the American Farmer. Green.
Farm Boys and Girls. McKeever.
The Training and Breaking of Horses. Harper.
Sheep-farming in North America. Craig.
Cooperation in Agriculture. Powell.
The Farm Woodlot. Cheyney and Wentling.
Household Insects. Herrick.
Citrus Fruits. Coit.

Principles of Rural Credits. Morman.
Beekeeping. Phillips.

Subtropical Vecjetable-gardening. Bolfs.
Turf for Golf Courses. Piper and Oakley.
The Potato. Gilbert.

THE POTATO

BY

ARTHUR W. GILBERT, Ph.D.

PROFESSOR OF PLANT-BREEDING, NEW YORK STATE COLLEGE
OF AGRICULTURE AT CORNELL UNIVERSITY

ASSISTED BY

MORTIEE F. BARRUS, Ph.D.

PROFESSOR OF PLANT PATHOLOGY, NEW YORK STATE COLLEGE
OF AGRICULTURE AT CORNELL UNIVERSITY

AND

DANIEL DEAN

FORMERLY PRESIDENT OF THE NEW YORK STATE
POTATO ASSOCIATION

THE MACMILLAN COMPANY
1917

All rights reserved

COPTBIGHT, 1917,

By the MACMILLAN COMPANY.

Set up and electrotyped. Published March, 1917.
Reprinted November, 1917.

NorbjooU ?3t£88

J. 8. Gushing Co. — Berwick & Smith Co.

Norwood, Mass., U.S.A.

PREFACE

This book is intended to give brief and practical
suggestions on the growing, breeding and marketing
of potatoes. It is written especially for the practical
farmer and the student who may wish concise informa-
tion on the potato without having to read many mis-
cellaneous sources of information, especially experiment
station bulletins which, although highly valuable, are
likely to contain much detail.

The chapters on breeding and varieties occupy an
unusually large proportion of the book. This is for the
reason that these subjects have been treated in potato
literature much less than methods of culture, and the
general interest in them has called for this extended
discussion to meet not only the necessities of the case
but also the public demand.

I have been glad to place in the hands of Doctor Bar-
rus and Mr. Dean the chapters on Diseases and Field
Methods respectively. These men have had broad ex-
perience in their lines and are thoroughly competent to
discuss them.

The author wishes, also, to acknowledge the valuable
aid of Professor Herrick in reading the manuscript on
Potato Insects, and Mr. A. C. Eraser and Mr. J. J.
Pollock for valuable assistance.

ARTHUR W. GILBERT.

Ithaca, New York,
January, 1917.

A y^cz.f\^A

CONTENTS

OHAPTBE ^a«^o

I. Acreage, Distribution, Production and Valu-
ation .....•••• 1-13
II. History • 14-20

III. Classification and Botanical Characteristics . 21-46

Description of the Irish potato — Classification
of varieties — Important varieties of Iowa and
the Central West — Tabulation of varieties —
Synonyms — Description of typical varieties.

IV. Potato Breeding 47-86

Ideals for the potato crop — Use of score card
— Possibilities of improving the potato — Meth-
ods of improvement — Improvement of the potato
by selection — Running out of varieties — Ap-
pearance of bud sports — Improvement by hy-
bridization.
V. Climate, Soils and Rotation .... 86-112
Factors influencing potato culture — Heat —
"Water requirements — Soil texture — Available
plant-food — Drainage and soil air — Critical
period — Type, variety and strain — Diseases —
General types of potato-growing in the United
States — Soils — Rotation — Hay plants.

VI. Manures and Fertilizers 113-132

Fertilizer practices — Market forms of fer-
tilizers — Nitrogen — Phosphorus — Potassium
— Calcium — Sulphur — Applying fertiUzers —
Farm manures.

vii

Contents

CHAPTER PAQES

VII. Planting 133-169

Tillage tools — Results of tillage — Planting —
Hill and drill planting — Planting tools — Hand
planting — Seed potatoes — Cutting seed.

VIII. Care of the Growing Crop 160-169

IX. Potato Insects and Their Control . . . 170-182
The Colorado potato-beetle — Flea-beetle —
Blister-beetle — The three-lined leaf-beetle —
Tortoise-beetles — The potato plant-louse —
Leaf-hoppers — The potato-stalk weevil — The
stalk-borer — White grubs — Wire- worms.

X. Diseases of the Potato 183-205

Classification of causes of disease — Early
blight — Late blight — Rhizoctoniose — Fusa-
rium wilt — Verticillium wilt — Fusarium dry
rot — Silver scurf — Potato wart — Common
scab — Black-leg — Bacteria wilt — Powdery
scab — Tip-burn — Arsenical injury — Spindling
sprout — Net-necrosis — Curly dwarf — Mosaic
leaf-roll — Constitutional degeneracy and other
weakened conditions of plants.

XL Control Measures against Diseases . . . 206-225
Control of curly-dwarf, mosaic and leaf-roll

— Field inspection — Seed treatment to prevent
disease — Disease from organisms already in soil

— Treatment for potato blight — Preparation of
bordeaux mixture — Other remedies — Disease-
resistant varieties — Summary.

XIL Harvesting the Potato 226-236

Time to harvest — Methods of digging — Pick-
ing and sorting — Labor and cost of harvesting.
XIII. Markets, Marketing and Storage . . 237-258

Marketing through local dealers — Marketing
the crop — Grading — Packages — Shipping —
Early and late potatoes — Markets — Range and
prices.

Contents ix

CHAPTER PAGES

XIV. Uses of the Potato 259-280

Use for human food — Quality when cooked —
Use for starch — Process of starch manufacture
— Uses of potato starch — Uses for industi-ial
alcohol — The manufacture of alcohol from pota-
toes— Use as stock food — Alcohol slops or resi-
due — Potato pomace — Poultry food — Dried
or desiccated potatoes — Potato flour.

XV. Cost of Growing Potatoes 287-313

Results of a survey in New York state — Other
survey results — Cost of hauling.

LIST OF PLATES

PLATE PACING PAGE

I. The potato as first grown in Europe ... 19

II. Types of potato tubers, as illustrated by the Wis-
consin Experiment Station .... 32

III. A plate of smooth potatoes with few and shallow

eyes — the breeder's ideal .... 48
(Photo by Farm Crops Dept., Cornell University)

IV. Illustration of good shaped potato for table use.

Variety, Green Mountain .... 51
(Photo by Farm Crops Dept., Cornell University)

V. Typical early and late potatoes. Top, Irish Cob-
bler (early). Bottom, Rural New Yorker

(late) 53

(Photo by Farm Crops Dept., Cornell University)

VI. Breeding. Each group of four plates represents the
progeny of a tuber, and each plate is the prod-
uct of a single hill ...... 56

VII. Tubers with histories. Upper, influence of growing
season, showing the second-growth tubers on
the right compared with the normal uniform
tubers on the left. Lower, breeding. — The
immunity and susceptibility of two tuber
progenies 61

VIII. Seed potatoes. Top, different ways of cutting.

Bottom, good and bad types for seed . . 100
xi

xii List of Plates

PLATE FACING PAGE

IX. Potato diseases. Upper tuber, rot caused by late
blight ; two bottom tubers, net necrosis. Leaf,
under surface, showing effect of late blight . 190
(Tuber cuts — Courtesy of Dept. of Plant
Pathology, College of Agriculture, Cornell

University)
(Leaf cut — Courtesy of the Geneva Agricul-
tural Experiment Station Bulletin 241, Plate
XII)

X. Potato diseases. Top, part of a potato leaf,
showing spots of early blight. Bottom,

rhizoctoniose 194

(Courtesy Dept. of Plant Pathology, College of
Agriculture, Cornell University)

XI. Potato diseases. Left, powdery scab. Right,

fusarium dry rot 196

(Courtesy Dept. of Plant Pathology, College of
Agriculture, Cornell University)

XII. SpindUng potato sprouts. Upper picture, rhizoc-
toniose ........ 198

(Courtesy Dept. of Plant Pathology, College of
Agriculture, Cornell University)

XIII. Preparing the bordeaux mixture .... 217
(Courtesy Dept. of Plant Pathology, College of

Agriculture, Cornell University)

XIV. The potato harvest. View in an eastern field . 232
XV. Combined potato digger and loader . . . 233

(Photo by W. C. Blake)
XVI. Potato products 259

THE POTATO

THE POTATO

CHAPTER I

ACREAGE, DISTRIBUTION, PRODUCTION AND
VALUATION

The potato is one of the most widely cultivated of the
agricultural plants. The esculent tubers, which are devel-
oped underground on slender leafless shoots or stems, are
used for food and also industrially. The plant is allied
botanically to several powerful narcotics, such as tobacco,
henbane and belladonna, and also to the tomato, egg-
plant and capsicum.

The potato comprises about 25 per cent of the food
of European and English-speaking peoples. Only the
Oriental peoples exist without it. A greater weight of
potatoes can be produced to a unit area than any other
food crop.

The yield in millions of tons of the world's most im-
portant plants is shown in the following table :

Table I. — World's Crops of the Most Important Food
Plants, in Million Tons. Average for 5 Years, 1908-
1912

Potatoes 161.0

Corn 128.38

Wheat 106.0

Oats 65.6

Ricei 55.6+

Rye 57.0

Barley 33.41

1 This figure does aot represent the rice crop of the world, as statistics
fFom certain sections of China are lacking.
B 1

nOPERU UBRARY

N. C. State CMtit

2 Tlie Potato

The average annual production of potatoes in the world
for the last ten years has been over 5,000,000,000 bushels.
The production of wheat, corn and oats has been approxi-
mately 4,000,000,000 bushels each. Potatoes, therefore,
lead the other crops in total production.

This immense total world production is generally and
widely distributed. The six leading countries and their
average annual production for the years 1911-1913, and
the average yields an acre for the years 1904-1913, are
as follows (see Fig. 1) :

Table II

Total Production
IN Bushels

Average Yield an
Acre in Bushels

Germany . .

European Russia

Austria-Hungary

France

United States .

United Kingdom

1,698,826,000
1,258,120,333
642,149,000
499,523,666
348,303,000
259,482,666

200.7
106.4
134.35
130.2
96.5
210.0

About 90 per cent of the world's crop is grown in
Europe, Germany and Russia producing more than half of
the total crop. The United States produces only about
one-fifth as much as Germany. This is largely due to
the fact that the German consumption per capita is about
two and one-half times as great as ours, and that more
than 50 per cent of the German crop is used either for
stock food or for conversion into starch, alcohol or other
industrial by-products. Potatoes, at present, are used
very little for these purposes in this country, less than 1
per cent being so employed.

Acreage and Value

Table III. — Percentage of World's Potato Crop ^ Pro-
duced BY THE Continents, and Principal Potato-pro-
ducing Countries. For the Years 1908-1912

Continents

Bushels

Per Cent
World's Crop

Europe . . .
North America
Asia ....
South America
Australia .
Africa . . .

4,817,830,200

425,239,800

54,329,000

38,931,000

13,813,600

4,793,200

89.72

7.92

1.01

.73

.26

.09

Principal Countries

Total Bushels

1908-1912,

Per Cent

World's Crop

Germany

Russia

Austria-Hungary

France

United States

1,624,801,000

1,209,513,400

664,538,200

514,542,200

346,119,200

30.25

22.52

12.39

9.58

6.45

The cultivation of the potato is now extended over most
of the agricultural sections of the Ignited States and
Canada and it is becoming increasingly important as an
article of human food in this country. It ranks sixth in
agricultural importance in the United States.

Table IV. — Relative Value op Crops in the United
States in Dollars (1908-1912)

Corn 1,512,780,000

Hay 768,330,000

Cotton 724,710,000

Wheat 666,940,000

Oats 412,360,000

Potatoes 209,720,000

Barley 107,710,000

Tobacco 94,429,000

» Average of world's crop for 1908-1912 = 5,369,590,000 bushela.

The Potato

Acreage and Value 5

The following table illustrates graphically the distribu-
tion of potato-growing in the United States (see Fig. 2).

In the United States, New York has led in potato pro-
duction for the last twenty-five years. The leading states
and yield to the acre are as follows : ^

Table V

State

Production in

Millions op

Bushels,

1911-1915

Yield to
THE Acre,
1906-1915

Average Price
A Bushel,
1906-1915

New York

Michigan

Wisconsin

Minnesota

Maine

Pennsylvania ....

3.3.35
33.27
32.80
30.04
25.67
23.13

97

94

102

102

204

85

Cents

63
59
87
44
54
68

In the last few years, Michigan, Wisconsin, Maine and
Minnesota have been rapidly gaining in production, and
are now all close rivals of New York.

For the ten years 1902-1911 inclusive, an average of
3,230,000 acres was devoted to the potato crop in the
United States, from which 304,158,000 bushels were pro-
duced, w^orth $177,503,000. This comprises only about
one-sixth of the w^orld's crop.

Ten states along the northern border, where the climate
is cooler and the crop is supplied with more moisture, pro-
duced nearly two-thirds of the potato crop of the United
States (see Figs. 3 and 4). Potatoes are grown, however,
in more or less quantity in every state of the Union.

As the agriculture in the United States becomes more

' After Montgomerj.'.

The Potato

Acreage and Value 7

stable and railroad facilities develop, there is more and
more of a tendency for farm crops to be intensively
grown in certain areas where soil, climate and other factors
are best suited to them. This is especially true of a crop
like corn or wheat which is neither perishable nor very
bulky and can be easily shipped. This is becoming

I £< 3S

Fig. 3. Percentage of the potato crop of the United States which is
produced in each of the 15 states of largest production, 1902-1911.

increasingly true of potatoes because of their bulkiness
and partial perishableness.

Most of the potatoes raised in the United States are
still grown as a cash crop in relatively small parcels on
many farms. There is a tendency, however, toward the
development of potato-growing centers in widely sepa-
rated sections of the United States. By a careful inspec-
tion of the map on page 6 one can see that these areas
are located in Aroostook County, Maine, the Norfolk and
Eastern Shore trucking regions of Virginia and Maryland,
the Red River Valley of Minnesota and North Dakota,
the Kaw Valley of Kansas, the Greely and Carbondale
districts of Colorado, and the San Joaquin and Sacramento
valleys of California.

The Potato

NFW VORK

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MICHIGAN

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MINNESOTA

PENNSYLVANIA

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IOWA

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=3

ILLINOIS

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Ed

COLORADO

CALIFORNIA

^^^

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DtiniAMA

^^m

VIRGINIA

■i^

■™

NEBRASKA

n_

pga

.

^■B

^H

3

MISSOURI

!■■■

WASHINGTON

^^

KANSAS

^^

"ZD

NORTH DAKOTA

«5"

KENTUCKY

5^

OREGON

■■5P

IDAHO

^■i

'

VERMONT

■■p

WEST VIRGINIA

^"

MARYLAND

^

SOUTH DAKOTA
MONTANA

^

^^B 1909
1 1 1899

MASSACHUSETTS

5

TENNESSEE

CONNECTICUT

!!b

UTAH

?

NORTH CAROLINA

?

NEW HAMPSHIRE

5

TEXAS ,

5"

ARKANSAS

5

OKLAHOMA

!P

LOUISIANA

P

ALABAMA

f

Fig. 4. Production of potatoes in the different states, 1909 and 1899.

Acreage and Value

9

The following tables from the thirteenth census indi-
cate the total number of farms in certain states where
potatoes were grown, the total yield and the total amount
to each farm. The latter figure shows that the total pro-
duction on most farms is in excess of the family con-
sumption :

Table VI

Bushels

Bushels

Bushels

State

County

TO A

Farm

County

to a
Farm

County

TO A

Farm

Mass.

Berkshire

128.5

Hampshire

112.3

Hampden

119.9

Vt.

Bennington

169.2

Chittenden

154.5

Addison

116.1

N. J.

Salem

636.8

Monmouth

643.8

Gloucester

389.1

Del.

Kent

44.3

New Castle

83.8

Sussex

101.4

W. Va.

Jackson

42.9

Wood

48.1

Preston

43.4

s. c.

Beaufort

39.9

Charleston

33.0

Colleton

29.4

Ga.

Chatham

189.4

Thomas

9.7

Union

11.0

Fla.

St. John

183.4

HiUsboro

22.1

Gadsden

13.7

111.

Cook

161.7

Madison

188.6

St. Clair

260.9

la.

Blackhawk

92.5

Grundy

489.8

Scott

358.5

Mo.

St. Louis

167.2

Buchanan

127.9

Ray

135.6

Neb.

Sioux

134.5

Douglass

134.2

Cherry

68.6

Ky.

Jefferson

386.5

Pike

25.0

Campbell

98.9

Ala.

Mobile

109.7

Jefferson

20.9

Dallas

3.8

Tex.

Harris

58.7

Cherokee

32.0

Cass

15.3

Wash.

Yakima

365.5

King

203.4

Pierce

166.7

Id.

Ada

89.6

Bingham

802.4

Lincoln

120.7

Af/f//V£
/V//V/V.

CAL/r

I/. -5.

23f %

S23

2.0d7o

Fig. 5. Percentage of the improved farm land that was annually
planted to potatoes in the ten leading states of the United States,
1902-1911.

10

The Potato
Table VII

Number
OF Farms

Total Yield

Total
Amount
TO A Farm

Yield

TO THE

Acre

FROM

Year-
book,
1914

Northern States

Massachusetts
Vermont . .
New Jersey .

36,917
32,709
33,487

2,946,178
4,145,630
8,057,424

79.8
126.7
240.6

125

155

90

Southern States

Delaware . .
West Virginia
South Carolina
Georgia . . .
Florida . . .

10,836

96,685

176,434

291,027

50,016

880,360
4,077,066
782,430
886,430
856,967

81.2

42.1

4.4

3.1

17.1

Northern Central States East of the Mississippi River

Ohio

Illinois

272,045
251,872

20,322,984
12,166,091

74.7
48.3

93
91

Northern Central States West of the Mississippi River

Iowa

Missouri

Nebraska

217,044
277,244
129,678

14,710,247
7,796,410
8,117,775

67.7
20.8
62.5

89

85
78

Southern Central States

Kentucky

Alabama

Texas

259,185
262,901
417,770

5,120,141
1,128,564
2,235,983

19.7

4.2
5.3

92
80
50

Far Western States

Montana

Washington ....
Idaho

26,214
56,192
30,807

3,240,696
7,667,171
4,710,262

123.6
136.4
152.8

180
170
200

Acreage and Value

11

It is not easy to determine the amount of the family con-
sumption of potatoes. It varies with different regions.
In a survey of 483 farm families quite widely scattered,
Funk found the average quantities and values of Irish
potatoes consumed annually to a person in the following
table :

Table VIII

State

Irish Potatoes

Bushels

Value

North. Carolina

Georgia

Texas

1.8
1.5
2.7

5.7
7.6
8.6
5.6
5.6
8.0
9.7

$2.13
2.32
3.24

4 40

Iowa

Wisconsin

Ohio

4.42
4.31
2 81

Pennsylvania

2.80
4 17

Vermont

3 98

Average

5.7

$3.45

The average, it will be seen, was 5.7 bushels to a person.
In the same survey was found an average of 4.6 persons
in the family, making a total of 26.22 bushels of potatoes
consumed to a family. Warren ^ gives the average quan-
tity of potatoes raised on the farm and used in the house
on 106 farms in Livingston County, New York, in 1909
as 50.3 bushels and the average amount to an individual
as 10.1 bushels. This is much higher than the figures
Funk obtained in his survey, but even at this high figure,
it is clearly seen that most farmers have at least a few
bushels of potatoes to sell.

1 Warren, G. F. "Farm Management," p. 24.

12 The Potato

In a farm management survey of Chester County,
Pennsylvania, by Spillman ^ it was found that the propor-
tion of income from potatoes on 378 farms in that county
was 8.9 per cent. On these farms, 6 per cent of the
crop area was devoted to potatoes. "They were found
on 366 of the 378 farms operated by owners. This crop
is, therefore, very general in this region, though the acre-
age of potatoes is usually small. On only seven farms was
the percentage of potato acreage found to exceed 20 (or 12
acres)." The farmers of this region grow at least enough
for home use and usually some for sale.

The yields to the acre are dependent upon many fac-
tors, the most important of which seem to be climate
and soil moisture. Yields to the acre in the United
States are low as compared with England or Germany.
The average yields of potatoes to the acre for the years
1901-1910 inclusive in the United States, Germany and
Great Britain were 92.7, 200.8 and 200 respectively.
European countries often grow the large, coarse, heavy-
yielding sorts for stock-feeding or for use in the arts, which
accounts for some of the difference in average yields.

In the United States, the average yield to the acre is
higher in Maine than in any, other state. The average
yield in the other states is usually 90 bushels or less.

Very large yields in the United States, however, are
not unheard of. A yield of 700 bushels to the acre in
Maine and the other potato-producing areas is not un-
common in very favorable seasons. Macoun, in speak-
ing of the possibilities of the potato, makes note of the
highest recorded yield of potatoes in this country. These
were grown by Mrs. Selinda E. Jones of Chautauqua

1 Spillman, Dixon and Billings. "Farm Management Practice of
Chester Co., Pa.," p. 26.

Acreage and Value 13

County, New York, in the Women's National Potato
Contest of 1888. She grew the White Elephant variety
on one-twentieth of an acre at the rate of 1061 bushels to
the acre.

In the United States the average yield of potatoes from
one plant is about one-half pound. Some plants of
Early Ohio have been known to yield thirteen tubers
weighing 2| pounds, and others of the same variety to
produce three tubers weighing ^ an ounce. The former
yield is 80 times the latter. Some English experiments
have produced twenty pounds of tubers to a plant, as
many as 150 tubers being set on one plant.

The climate of Canada is well suited to the produc-
tion of potatoes. The cool summers produce a yield to
the acre that compares very favorably with the best
regions of the United States. The average number of
acres devoted to this crop for the years 1910-13 was
476,000, upon which an average yield of 152.46 bushels
to the acre was secured, making an average total yield
for the four years of 72,569,000 bushels.

In the five fiscal years 1910-14, Canada exported an
average of 1,451,990 bushels of potatoes each year, of
which 376,406 bushels were sent to the United States.

CHAPTER II
HISTORY

The early history of the potato is a matter of some
doubt among historians, but all are agreed that it came
originally from the high lands of Peru and Chile, where it
is still found growing wild.

The Spaniards first discovered the potato in the neigh-
borhood of Quito, Ecuador, where it was cultivated by the
natives. According to Pedro Cie^a de Leon, who seems
to have made first written mention of the potato in his
"Spanish Chronicles of Peru" (1550), the inhabitants
subsisted largely on maize and what they called "papas"
and "quinua." The former is the Indian name for
potato and the latter "is a plant about the height of a
man and has leaves like the blite of Mauritania, and a
small seed either red or white in color, from which is
prepared a drink, and a food comparable to our rice."

Potatoes were used by the aborigines in place of bread,
and were also dried in the sun to preserve them. They
were usually cooked, but often made into flour. There
was evidence of long-continued practice of cultivation,
however crude. The potato, however, was and still is
wild in the mountainous regions of Chile and Peru.

The potato was probably carried to Spain by explorers
in the sixteenth century. There is no definite record of
this first importation, but Rose believes that it jvas as
14

History 15

early as 1533 or 1535, at the time of the conquest of Peru
by the Spaniards, Hieronymus Cardan, a monk, is
supposed to have been the first to introduce it from
Peru into Spain, and from thence it passed quickly into
Italy, Austria, Germany, Switzerland, Belgium and
France. The first figures and detailed description of it
in its new home in continental Europe are those of Clusius
in 1601 in his " Rariorum Plantarum Historia," although
Bauhin in his " Phytopinax," printed in Basel in 1596,
described it and gave it the Latin name or characteriza-
tion, Solanum tuberosum esculentum. (See Plate I.)

The date and method of introduction of the potato
into North America are not definitely known, but it was
probably introduced by Spanish voyagers and at some-
time before 1585, for it is clearly recorded that its first
introduction was made into England by colonists from
Virginia in 1586 under the patronage of Sir Walter
Raleigh.

"It seems to me most likely," says De CandoUe, "that
some inhabitants of Virginia — perhaps English colo-
nists— received tubers from Spanish or other travelers,
traders or adventurers, during the ninety years which
had elapsed since the discovery of America. Evidently,
dating from the conquest of Peru and Chile, in 1535 to
1585, many vessels could have carried tubers of the potato
as provisions, and Sir Walter Raleigh, making war on
the Spaniards as a privateer, may have pillaged some
vessel which contained them. This is the less improbable,,
since the Spaniards had introduced the plant into Europe
before 1585."

At the discovery of America, we are told by Humboldt,
the plant was cultivated in parts of western South
America from Chile to Colombia but not in Mexico, and

16 The Potato

there is no account of its being found wild in other parts
of North America.

From 1585 or 1586, potato tubers were brought from
what is now North Carohna to Ireland on the return of
the colonists sent out by Sir Walter Raleigh, and were
first cultivated on Sir Walter's estate near Cork. This
was some years later than their introduction into conti-
nental Europe.

In 1629, Parkinson in his " Paradisus," in which he gives
an indifferent figure of the potato under the name of
Papas seu Battatas Virginianorum, adds details as to the
method of cooking the tubers which seems to indicate
that they were still luxuries.

The cultivation of the potato in England made little
progress for many years. It is said that in the time of
James the First, they were so rare as to cost two shillings
a pound, and are mentioned in 1619 among the articles
provided for the royal household. In 1633, when their
valuable properties had become more generally known,
they were deemed worthy of notice by the Royal Society,
which took measures to encourage their cultivation and
for introduction into Ireland, especially as a safeguard
against famine, but their cultivation has become general
only within the last one hundred years.

John Gerard received some tubers of the potato from
Virginia and planted them in his garden. He gave a
careful description of them in his "Herbal," the first
edition of which was published in London in 1597. In a
later edition (1636) he pictures them by means of a wood-
cut (see Fig. 6). He was so proud of these plants that
he was represented in his portrait at the beginning of
the work holding a flowering branch of the plant in his
hand.

History

17

It should be noticed how closely the description of the
potato at this early date corresponds with the plant as
grown to-day. He says : " Virginia potato hath many
hollow, flexible branches trailing upon the ground;
these are square,
uneven, knotted or
kneed in sundry
places at certaine
distances : from
the which knots
Cometh forth one
great leafe made of
divers leaves, some
smaller and other
greater, set to-
gether upon a fat
middle rib by
couples, of a swart
green colour tend-
ing to redness ; the
whole leaf resem-
bling those of the
Winter-Cresses, but
much larger ; in
taste at the first
like grasse, but af-
terwards sharp and
nipping the tongue.
From the bosome of which leaves come forth long round
slender foot stalkes, whereon grew very faire and pleasant
floures, made of one entire whole leafe, which is folded or
plaited in such strange sort, that it seems to be a floure
made of five sundry small leaves, which cannot easily be

Copy of the engraving of the Vir-
ginian potato in Gerard's "Herbal" — printed
in 1636.

18 The Potato

perceived, except the same be pulled open. The whole
floure is of a light purple colour, striped downe the middle
of every fold or welt with a light show of yellownesse, as
if purple and yellow were mixed together. In the middle
of the floure thrusteth forth a thicke flat point all yellow
as gold, with a small sharpe greene pricke or point in
the midst thereof. The fruit succeeds the floures, round
as a ball, of the bigness of a little Bullesse or wild plumme,
green at first, and blacke when it is ripe, wherein is con-
tamed small white seed lesser than those of mustard ;
the root is thick, fat, and tuberous, not much differing
either in shape, colour or taste from the common potatoes,
saving that the roots hereof are not so great nor long;
some of them are as round as a ball, some oval or egge-
fashion, some longer and others shorter; the knobby
roots are fastened unto the stalkes with an infinite num-
ber of threddy strings. It groweth naturally in Americus
where it was first discovered, as reporteth Clusia, since
which time I have received roots hereof from Virginia,
otherwise called Norembega, which grow and prosper in
my garden as in their own native country. The leaves
thrust forth on the ground in the beginning of May ; the
floures bud forth in August, the fruit is ripe in Septem-
ber. The Indians call this plant pappas, meaning roots,
by which name also the common potatoes are called in
those Indian countries. We have its proper name men-
tioned in the title 'Potatoes of Virginia.' Because it
hath not only the shape and proportion of potatoes but
also the pleasant taste and vertues of the same, we may
call it in English, Potatoes of America or Virginia."

In 1769, the grain crops of France were a failure, threat-
ening a national famine. Parmentier, a Parisian chemist,
recommended the use of potatoes as food to take the

History 19

place of the grain crops. He had been a member of the
medical staff of the French army in 1758, during the war
in Hanover, and had been taken prisoner. During his
five years in prison his principal food consisted of potatoes,
which were then grown almost exclusively as food for
animals. The dire need of food in France inspired him
to write a book called a "Treatise on Certain Vegetables
that in Times of Necessity can be substituted for Ordinary
Food." This book was received with ridicule even
though it received a certain amount of support from the
Paris Agricultural Society. By persistent efforts, Par-
mentier was granted a small patch of land on which to
experiment with his potatoes. The king ordered the
plot to be guarded by a cordon of troops which excited
the curiosity of the people. On August 24th, the king's
fete-day, he presented the king with a basket of tubers
and a bouquet of the blossoms. These were worn by the
king and queen, who also ate the cooked tubers. They
were found to be very palatable and soon became one of
the foods of the French people.

During the seventeenth century, the potato gradually
became, from a botanical curiosity cultivated only by
collectors of new plants, one of the staple garden and field
crops. Its cultivation as a field crop became somewhat
common in Germany soon after 1772, when the grain
crops failed and potatoes were used as a substitute. The
quality was very poor, however, and even though they
were enormously productive, their use was restricted
largely as food for domestic animals and they were used as
human food only when necessary as a substitute. By
the latter half of the eighteenth century, it was exten-
sively cultivated and recognized as one of the regular
crops throughout the temperate regions of Europe and

20 The Potato

America, so that Henry Phillips (1822), who published a
detailed account of the potato and its culture, was able
to cite a single grower who planted 300 acres annually.

In Ireland, they were used very extensively as human
food. By 1840 they had largely replaced the cereals and
similar food crops because their yield in weight exceeded
by twenty to thirty times the yield of wheat, barley or
oats on an equal amount of land. Dependence upon a
single crop for food, however, became disastrous for the
Irish. The potato blight which appeared in the United
States in 1845 devastated Ireland in 1846 and caused
a widespread famine. It is conservatively estimated
that 600,000 persons died during the two years 1846 and
1847 for want of food or from diseases caused by a meager
diet of unhealthy and unnutritious food. By 1848 the
plague had practically ceased.

REFERENCES

Campbell, W. H. W. The Father of the Potato. Cosmopolitan,

Vol. II, pp. 191-192. 1SS6.
De Candolle, Alphonse. Origin of Cultivated Plants. 1-468,

N. Y., 1892.
Del'Ecluse (ofClusius). RariorumPlantarumHistoriae, 1601, lib.
Gerard. Herbal. 1597, p. 781, with illustration.
Meckel, E. The Origin of the Cultivated Varieties of the Potato.

Rev. Sci. (Paris), 60: 1912, II, No. 21, pp. 641-646.
Henslow, Geo. The Origin and History of Our Garden Vegetables

and Their Dietetic Values. II. Roots + tubers (cont.).

Roy. Hort. Soc. Journ., 36: pp. 345-346, Figs. 120-

121 (1910-1911).
Rose, Ernest. Histoire de la pomme de terre traitee aux points de

vue historique, cultural ct utilitaire. 1-464 Par. 1898.
Sabine, J. On the Native Country of the Wild Potatoes. Trans.

Hort. Soc. London, Vol. V, pp. 249-259. 1824.

CHAPTER III

CLASSIFICATION AND BOTANICAL CHARAC-
TERISTICS

The common or Irish potato is known botanically as
Solarium tuberosum. This name was first appHed to it
by Bauhin in his "Phytopinax" in 1596 (page 15) and
later adopted by Linnaeus. In the same family (Solana-
cese) are many other plants of economic importance, as
tomato, eggplant, tobacco, belladonna, henbane and cap-
sicum or red-pepper.

Baker has reviewed the tuber-bearing species of Solanum
from a systematic point of view as well as that of geo-
graphic distribution. Out of twenty so-called species he
considers six to be really distinct, while the others are
synonymous or trifling variations. The six admitted
tuber-bearing species are S. tuberosum, S. Maglia, S. Com-
mersonii, S. CardiophyUum, S. Jamesii and S. oxycar-
pum. See also "Standard Cyclo. Hort." VI, 3181.

The following descriptions of species have been taken
from Baker's "A Review of Tuber-bearing Species of
Solanum" — Linnsean Soc. Journ. Bot., XX: pp. 489-
507, pis.

Solanum tuberosum, Linn. — vStems stout, erect, much branched,
1-2 feet long, slightly hairy, distinctly winged on the angles. Leaves
1-2 feet long, slightly hairy, with 7-9 finely pilose oblong acute leaf-
lets, the side ones stalked and unequally cordate at the base, the 1-2
lowest pairs much dwarfed, petiole about 1 inch long. Numerous
small leaflets between larger ones. Flowers in compound terminal
cymes with long peduncles. Corolla wheel shaped, dark lilac,
21

22 The Potato

nearly 1 inch in diameter. Calyx hairy, \-^ inch long, with teeth
as long as or a little longer than the campanulate tube. Berry
globose, less than an inch in diameter, smooth. Native of Chile
and Ecuador.

Solatium Maglia, Schlecht. — Stems stout, erect, much branched,
1-2 feet long, strongly winged on angles, slightly hairy. Leaves
6-9 inches long, larger leaflets 5-7, ovate acute, 2-3 inches long, side
ones stalked, unequally cordate at base. Flowers in compound
cymes; pedicles downy. Corolla white, subrotate, f to 1 inch in
diameter. Style twice as long as the stamens. Fruit not seen.

Solanum Commersonii, Dunal. — Stems shorter and more slender
than in S. tuberosum. Leaves 5-6 inches long, with a naked petiole
1-1 1 inches long; 5-9 oblong acute leaflets, the terminal one much
the longest; the rachis entirely without any of the small leaflets
interspersed among the large ones. Flowers in lax compound cymes.
Calyx ^-j inch long. Corolla pale lilac or white. Anthers orange-
yellow. Style distinctly exserted beyond the anthers. South
America.

Solanum cardiophyllum, Lindley. — Of the same general habit as
S. tuberosum. No small leaflets interspersed amongst the large
ones. Whole plant quite glabrous. Foliage very dark green.
Leaflets 5, large, ovate acute. Flowers in compound cymes. Calyx
glabrous. Style scarcely longer than the stamens. Mountains of
Central Mexico at an elevation of 8000-9000 feet.

Solanum Jamesii, Torrey. — Minute globose tubers. Leaves dis-
tinctly petiolate, with .5-9 oblong acute leaflets ; no smaller leaflets
interspersed amongst the longer ones. Cymes few flowered. Co-
rolla white. Fruit globose. Mountains of southwestern United
States and Mexico.

Solanum oxycarpum, Schiede. — Tubers minute. Leaflets 5-9,
oblong lanceolate, with no smaller leaflets interspersed amongst the
larger ones. Cymes few flowered. Fruit ellipsoidal.

DESCRIPTION OF THE IRISH POTATO

The common potato owes its value to the peculiar
habit of developing underground slender leafless shoots
or branches which differ in character and office from
the true roots, and gradually swelling at the free end

Description and Classification 23

produce the tubers (potatoes), which are the common
vegetable food. The nature of these tubers is further
rendered evident by the presence of "eyes" or leaf-
buds, which in due time lengthen into shoots and form
the haulm or stems of the plant. Such buds are not,
under ordinary circumstances, formed on roots. This
budding of the tubers furnishes an efficient method
of propagation, independent of seed production. Starch
and other matters are stored up in the tubers, as in the
seed, and are rendered available for the nutrition of the
young shoots. When grown under natural circumstances,
the tubers are relatively small, and close to the surface
of the soil, or even lie upon it. In the latter case, they
become green and have an acrid taste, which renders them
unpalatable to human beings, and as poisonous qualities
are produced similar to those of many Solanacese, they
are unwholesome. Hence the recommendation to keep
the tubers in cellars or pits not exposed to the light.
Among the 900 species of Solanum, less than a dozen
have this property of forming tubers. The production
of small green tubers on the haulm, in the axils of the
leaves of the potato, is not very infrequent, and affords
an interesting proof of the true morphological nature of
the underground shoots and tubers. This phenomenon
follows injury to the phloem in the lower parts of the
stem, preventing the downward flow of the elaborated
sap.

CLASSIFICATION OF VARIETIES. PLATE II

For the sake of convenience, the many varieties which
are now on the market may be classified. No one classi-
fication, however, will be adequate to cover all conditions.
Varieties differ somewhat from one part of the country

24 The Potato

to another. Most standard varieties have many syn-
onyms which make the whole matter more confusing.
The frequent appearance of new names for old varieties
is as much the fault of the grower as it is of the seedsman.
There is a strong demand for new things. The seeds-
man attempts to meet this, but most of our seedsmen
are professedly not originators of new varieties, and the
supply of strictly new varieties must, of necessity, be
very limited, hence the demand is met by changing the
name of some old variety and giving extensive advertis-
ing under its new name. The gullible grower accepts
the dose, pays the price for the supposedly new article
and is satisfied until he learns that it is nothing new and
then he turns around and repeats the process again.

The number of named varieties is so large that the
chances of finding something far superior are very slight.
However, it is not at all impossible to find such a variety if
one has the patience to look for it or the skill to produce it.
However, for the average grower, it is much better to stick
to the old standard sorts which are recognized in the mar-
ket. If better varieties are demanded, it is wiser, in gen-
eral, to start with standard varieties which have already
reached some degree of perfection and improve them.

The potato is very susceptible to differences in soil
and climate, and varieties often lose their distinguishing
characteristics when grown under what might be con-
sidered unusual environment. There has also grown up,
of course, a wide range of opinion as to what the standards
of certain varieties are. The standard of a variety in
one locality may be very different from the accepted
standard of that same variety in another locality. The
introduction of new varieties which may be but slight
variations from the old sorts has still further complicated

nOrERTY LlBRARt
mf r Qf^*M fnllfite

Description and Classification 25

the situation. Moreover, many so-called new varieties
are merely the old varieties under a new name. But on
the whole, the old standard varieties may be recognized
fairly accurately.

Potatoes may be classified according to the shape of
the tubers. "Tubers are not always of the same form;
three moderately distinct and fairly constant types are
prevalent, namely, (1) round, (2) oval and (3) kidney
shapes. The round type is somewhat spherical and has
fewer internodes and 'eyes' than the oval or kidney-
shaped potatoes. The kidney potatoes are thickest at
the stem or basal end and taper gradually at the apex
or seed end, while the oval varieties are thickest in the
middle and taper towards both ends (see Fig. 7). These
differences are sufficiently marked and constant for a
comparison of the varieties in cultivation." — Percival.

Important varieties of Iowa and the Central West

C. L. Fitch,^ of the Iowa State College, made a thor-
ough trial for a series of years of all varieties of commercial
importance in the United States and Europe. He made
also a canvass in person and by letter of the markets
of the United States. The result was that only a few
varieties were found to be of much commercial impor-
tance. He lists the following varieties as being the most
valuable in the United States in order of their importance :

1. Rural 5. Irish Cobbler

2. Green Mountain 6. Bliss Triumph

3. Early Ohio 7. Peerless (Pearl)

4. Burbank

1 Fitch, C. L. "Identification of Potato "Varieties." Iowa Extension
Bui. 20 (1914).

26

Tlie Potato

Description and Classification 27

Fitch says that the varieties Rural, Early Ohio and
Irish Cobbler are the outstanding varieties of Iowa. In
regard to the others, he makes the following comments :

"The following are grown in Iowa to a greater or less
degree or reach our markets.

" Green Mountain, the second most important variety
in the United States, and a second best late sort for Iowa.

" Burbank, still the standard of the U. S. Government
for market quotations, formerly important in Iowa, and
at some seasons still important in the supply of her cities.

" Peerless or Pearl, by test at Ames, ranking among the
best late sorts, and often coming into her markets from
Colorado or Wisconsin.

" Bliss Triumph, sometimes grown in Iowa for very early
use, and extensively grown in the South for the supply
of the early markets of Iowa and the northern states."

William Stuart of the United States Department of
Agriculture has recently made a very comprehensive and
admirably arranged classification of potatoes. His bulle-
tin contains not only a valuable key, but a careful descrip-
tion of our standard varieties of potatoes and points out
many unnecessary synonyms. The reader is referred
to this bulletin for this storehouse of information on
potato varieties.

Stuart gives the following classification key :

Stuart's cldssificution
Group 1. — Cobbler.

Tubers : Roundish ; skin creamy white.

Sprouts : Base, leaf scales and tips slightly or distinctly tinged
with reddish violet or magenta. In many cases the color is
absent.
Flowers : Light rose-purple ; under intense heat may be almost
white.

28 The Potato

Group 2. — Triumph,

Tubers : Roundish ; skin creamy white, with more or less numer-
ous splashes of red, or carmine, or solid red; maturing very
early.

Sprouts : Base, leaf scales and tips more or less deeply suffused
with reddish violet.

Flowers : Very light rose-purple.

Group 3. — Early Michigan.

Tubers : Oblong or elongate-flattened ; skin white or creamy
white, occasionally suffused with pink around bud-eye cluster
in Early Albino.

Sprouts : Base light rose-piu-ple ; tips creamy or light rose-purple.

Flowers : Wliite.

Group 4. — Rose Group.

Tubers : Elongated or oblong, usually flattish at the center and
tapering gradually toward each end ; stem and seed end rather
blunt. Skin smooth, flesh color. Flesh creamy white, some-
times streaked with red.

Sprouts : Rather long, medium thick, and usually clearly tinted
with rose-lilac.

Group 5. — Early Ohio Group.

Tubers : Round-oblong with full, rounded seed and stem ends.

Eyes numerous and rather shallow. Skin or flesh light pink

with a deeper color around the eyes.
Sprouts : Short, much enlarged at the base, color varying from

carmine-violet to violet-lilac or magenta-lilac.

Group 6. — Hebron Group.

Tubers : Elongated, somewhat flattened, \vitli rather blunt ends,
occasionally spindle shape. Eyes numerous. Skin creamy
white, more or less clouded with flesh color or light pink.

Sprouts : Very similar to those of the Early Rose Group.

Description and Classification 29

Group 7. — Burbank Group.

Tubers : Long, cylindrical or slightly flattened in shape. Eyes
numerous and rather shallow. Skin white to dull white,
smooth to glistening, or sometimes russeted.

Sprouts : Base creamy wliite or faintly tinged with magenta.

Flowers : Wliite.

Group 8. — Green Mountain Group.

Tubers : Broadly roundish-flattened to distinctly oblong-flat-
tened ; ends usually blunt, especially the seed end. Eyes rather
shallow. Skin dull creamy white, more or less netted.
Sprouts : Rather short and stubby. Wliite or faintly tinged.
Flowers : White.

Group 9. — Rural Group.

Tubers : Round-flattened to broadly roundish — oblong or dis-
tinctly oblong. Eyes few ; very shallow. Skin creamy white
and occasionally netted.

Sprouts : Short, base enlarged, dull white.

Flowers : Of fair size. Central portion of corolla deep violet-
purple, shading to a lighter tone toward outside edge.

Group 10. — Pearl.

Tubers : Round-flattened to heart-shape flattened, usually heavily

shouldered ; skin dull white, dull russet, or brownish white in

section 1 or a deep bluish purple in section 2.
Sprouts : Section 1 — base, leaf scales and tips usually faintly

tinged with lilac ; section 2 — base, leaf scales and tips vinous

mauve.
Flowers : White.

Group 11. — Peachblow.

Tubers : Round to round-flattened or round-oblong ; skin creamy
white, splashed with crimson or solid pink ; eyes usually bright
carmine. Includes some early-maturing varieties.

Sprouts : Base, leaf scales and tips more or less suffused with
reddish violet.

Flowers: Purple.

30 The Potato

Group types according to Fitch

Group 1. — Rural.

Tuber shape : Wide and flat types when at best. Ends rounded

much hke stem and usually not recessed. (See Fig. 7.)
Tuber and eye color : Blinds, white. First sprouts yellow or

waxy white with bluish violet tips which change, on exposure

to light, to dark or dull purple.
Root stubs : Yellowish white ; free from purple.
Stem : Erect and touched with brownish purple.
Foliage : Green, darkened by the purple, and in state much more

acrid than "all-green" foliage.
Blossom : Bluish violet- white.

Group 2. — Early Ohio.

Tuber shape : Somewhat flattened and slightly tapering, with

stem end a least bit recessed. Eyes are unevenly distributed

and numerous. (See Fig. 7.)
Tuber and eye color : Skin brownish pink, almost white to red,

changing, on long exposure to light, to a weathered gray brown.

First sprouts are white or greenish white with lilac tips.
Foliage : Medium green.
Blossoms : Lilac-white.

Group 3. — Irish Cobbler.

Tuber shape : The finest type is flat and wide like good Rurals
but there is a very distinct round, rough, deep-eyed type formed
in poorer conditions. In some cases large types are pear
shaped and rough like the largest Rurals and may combine
the pear shape with the heavy eyebrow types of the Rural.

Tuber and eye color : Skin smooth yellowish white, changing in
the light to dull olive-green with a suggestion of blue. Blinds,
white. Sprout-leaves, hairy, light green.

Blossoms : Pink with white tips on petals. Wliite blossoms not
found on Cobblers.

Group 4. — Green Mountain.
Tuber shape : The waisted or dumb-bell type is characteristic.
Stem end somewhat recessed. (See Fig. 7.)

Description and Classification 31

Tuber and eye color : A fine smooth and quite brown netting is a

feature of many of the tubers. An "all-white" variety.
Foliage : Bright green.
Blossoms : White. Buds yellow.

Group 5. — Burbank.

Tuber shape : Long, largest at center. Best type, shorter, wide,

and flattened. Poor type, spindle shaped. Stem end flush.

Eyes shallow or flush. In poor conditions very subject to knots.

(See Fig. 7.)
Tuber and eye color : Blinds, white. Skin white changing in

light to greenish gray brown. First sprouts white with light

green tips.
Foliage : Bright green.
Blossoms : White. Buds yellow.

Group 6. — Peerless or Pearl.

Tuber and eye color : Skin, white, or if ripened well, brownish
white, coarsely cracked. Skin turns dull green in light. (See
Fig. 7.)

Blossoms : White, when borne. Buds, white or greenish white.

Stem and foliage : Vigorous, bright green.

Group 7. — Bliss Triumph.

Tuber shape : More or less roughly globular, recessed stem.
Large tubers somewhat oval or nosy. (See Fig. 7.)

Tuber and eye color : Pink to red-brown skin changing in light
to grayish red brown. Blinds, pink to red brown. Sprout-
leaves, dark apple-green.

Groups according to Kohler

Group L — Tuberosum Group.

Characterized by foliage of the wild Solanum type. Tubers of
varying shape, usually with rather deep eyes; below medium
in size.

Foliage relatively resistant to disease.

32 The Potato

Group 2. — Rural Group.

Rural New Yorker is the type of the group. Tubers character-
istically short, smooth and flattened. Skin white. Eyes
generally shallow.

Group 3. — Leo Group.

Plants upright in habit; little or no purple in stems. Tubers
roundish or somewhat elongated with uneven siu-face.

Group 4. — Woltman Group.

Plants medium erect; foliage fairly dense. Tubers similar to
those of Leo group. Group not very well defined.

Group 5. — Endurance Group.

Plants very recumbent ; leaves pure green. Tubers light in color ;
elongated to medium in length.

Group 6. — Factor Group.

Plants fairly erect, with dense foliage. Tubers generally roundish
or short elliptical ; comparatively even surface.

Group 7. — Sharpe's Express.

Plants moderately erect; foliage dark green. Tubers rounded
or slightly elongated and surface comparatively even. Flowers
white.

Group 8. — Green Mountain Group.

Plants medium upright ; stem free from purple. Tubers medium
in length with a tendency toward oblong form; white and
slightly netted skin. Eyes sunken somewhat.

Plate II. — Types of potato tubers, as illustrated by the Wisconsin

Experiment Station.

A careful selection of seed for a few years will gradually elinainate these

undesirable types.

Description and Classification 33

Group 9. — Michigan Group.

Michigan variety typical of the group. Tubers somewhat elon-
gated; skin fairly smooth. A composite group with char-
acters not well defined.

Group 10. — Ohio Group.

The Early Ohio is typical of this group. Tubers oval in shape
and only slightly compressed; eyes numerous and usually
shallow. Sm"face quite even.

Group 11. — Cobbler Group.

Plants upright in habit. Tubers white, pink or red; variable
in shape and size.

Groups according to Milward
Group 1. — Round White Group.

Tubers : round to oval and slightly flattened. Surface generally

netted. Skin white and flesh white.
Flowers : white or purple.

Group 2. — Long White Group.

Tubers : Long oblong in shajje and sometimes flattened. Skin
and flesh white.

Tabulation of varieties

The varieties of potatoes mentioned and described by
Stuart, Milward, Kohler and Fitch have been brought
together in one table for convenience. Each variety so
far as possible has been classified by naming the group
into which it has been placed by one or more of the authors
named. In this way, it is easy for any person to get an
idea of a variety if he is unfamiliar with it by referring
to the description of the group into which the variety is
placed :

34

The Potato

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Description and Classification

35

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36

The Potato

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Description and Classification

37

The Potato

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Description and Classification

39

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The Potato

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Description and Classification

41

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42

The Potato

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Description and Classification 43

Synonyms

Frequently potatoes belonging to well-recognized va-
rieties are renamed and sold as distinctly new sorts.
This practice may be due to the fact that the seedsman,
or the grower, is not familiar with all the standard va-
rieties ; or it may be a fraudulent attempt to induce the
farmer to pay a high price for seed of a supposedly new
and superior variety. Then, too, the same type may
arise in different parts of the country at about the same
time and be given different names in each locality. Be-
cause of these conditions we often have one variety mas-
querading under a number of different trade names. It
is desirable that a single name be chosen for each distinct
type, and that that name alone be used to designate
tubers of the standardized type. The following list of
synonyms, adapted from Stuart, may be found helpful
in straightening out variety names :

Synonym Preferred Name

Acme Early Acme

Black Mercer Black Chenango

Bliss Triumph Triumph

Bhie Noses Mercer

Boston Market Early Sebec

Bresee's No. 2 Bresee's Prolific

Bresee's No. 4 King of the Earlies

Bresee's No. 6 Peerless

Bruce's White Beauty White Beauty

California Russet Russet Burbank

Chenango Mercer

Chenango Wliite Mercer

Early Bovee Bovee

Early Henry Early Shaw

Early Hunt Triumph

Early Pinkeye Dykeman

44

The Potato

Synonym

Early Sunlight

Early Victor

Early Wenvvell

Ensign Bagley

Farmer Hasting

Improved Early Rose

Improved Manistee

Junior Pride

Knowles's Big Cropper

La Plata Red

Late Hoosier

Lookout Mountain

Maine Rose

Merino

Meshanock

Mashannocks

Nephannocks

Neshannocks

New Blush

New Minister

Nishenock

Page's Extra Early Surprise

Peachblow

Peachblow

Philadelphia

Pride of the South

Queen of the West

Red Bliss

Red Mercer

Red Six Weeks

Rose No. 4

Round Pinkeye

Rural New Yorker (No. 1)

Rural Russet

Six Weeks

Spanish

Stray Beauty

Vermont Champion

Preferred Name

Sunlight

Victor

Wendell

Clark's Pride

Farmer

Early Rose

Early Manistee

Wliite Triumph

Knowles

Long Red

McCormick

McCormick

Early Maine

Long Red

Mercer

Mercer

Mercer

Mercer

Rm-al Blush

Minister

Mercer

Early Surprise

Jersey Peachblow

Western Red

Mercer

White Triumph

Maggie Murphy

Triumph

Long Red

Triumph

Spaulding No. 4

Dykeman

Carman No. 1

Late Petoskey

Early Six Weeks

Long Red

Triumph

Champion

Description and Classification 45

Synonym Preferred Name

Weld's Jumbo Jumbo

White Bliss Pride of the South

White Chenango Mercer

White Early Ohio White Ohio

White Elephant Late Beauty of Hebron

White Meshannock White Mercer

White Triumph Pride of the South

Willard Seedling WiUard

DESCEIPTION OF TYPICAL VARIETIES

Below are given brief descriptions of the more popular
varieties. These descriptions have been taken largely
from Stuart : ^

Burbank. — Originated by Luther Burbank in 1873 ; claimed to
be a seedling of the Early Rose. Season medium late. Tubers
large, round, long; eyes shallow, but rather numerous; skin nearly
smooth, white; flesh firm, fine grained, of excellent flavor when
cooked.

Carman No. 1 (Rural New Yorker No. 1). — Originated by
E. S. Carman in 1889. Seedling of other seedlings. Season medium.
Very few, shallow eyes ; quality excellent ; flesh white. Vines very
stocky.

Country Gentleman. — Originated by G. W. P. Jerrard Co. Sea-
son medium late. Vines of medium vigor and spreading habit;
flowers white. Tubers long, cylindrical ; eyes medium ; skin Hght
buff; flesh white.

Early Rose. — Originated by Albert Bresee in 1861. Season
early. Vines stout, erect; leaves large. Tubers quite smooth;
nearly cylindrical, tapering toward each end; eyes shallow; skin
thin, tough, and of a dull blush color ; flesh white, solid, brittle.

Green Mountain. — Originated by O. H. Alexander in 1878.
Claimed to be a seedling for a cross between Dunmore and Excel-
sior. Season medium late. Vines vigorous, with dark green
foliage. Tubers short and chunky, flattened, not very regular;

1 Stuart, Wm. U. S. D. A., Prof. Paper, Bui. 176, 1915.

46 The Potato

eyes sometimes considerably depressed; skin nearly white; flesh
fine grained.

Irish Cobbler. — Of unknown origin. Season extra early.
Tubers nearly round, large ; eyes good ; skin russet, finely netted ;
flesh white. Similar or identical with variety Eureka.

Pearl, Midseason. — Vines strong, medium to large ; stems me-
dium dark green, rather stocky; erect at first, bending over as the
season advances. Leaves large, flat, medium dark green. Flowers
wliite. Tubers medium to large, round-flattened to heart-shaped,
flattened, usually broader at the stem end ; pinkish tinge about the
eyes, especially when freshly dug; skin dull white or light russet,
usually roughened or cracked ; flesh solid and quite heavy.

Rural New Yorker No. 2. — Originated by E. S. Carman. Intro-
duced into trade about 1889. Season medium late. Vines tlirifty
and strong. Tubers oblong, inclined to round or round-oval, rather
flattened ; eyes few, shallow ; skin pure white netted ; flesh wliite.

Sir Walter Raleigh. — Originated by E. S. Carman. Claimed to
be a seedling of Rural New Yorker No. 2. Introduced into trade
in 1897. Vines similar in habit and color of flowers to those of
Rural New Yorker, No. 2, but color of stems not as pronounced.
Color of flesh and skin of tubers is the same; quality better than
that of Rural New Yorker No. 2.

REFERENCES

Baker. A Review of Tuber-bearing Species of Solanum. Linn.

Soc. Journal Bot., 20 : pp. 489-507, pis.
Fitch, C. L.

Identification of Potato Varieties. Iowa Extension Bui. 20. 1914.
KOHLER, A. R.

Potato Experiments and Studies at University Farm in 1909.
University of Minnesota Bui. 118. April, 1910.
MiLWARD, J. G.

Conmiercial Varieties of Potatoes for Wisconsin. University of
Wisconsin Bui. 225. July, 1912.
Percival, John. Agricultural Botany, pp. 439-451.
Stuart, Wm.

Group Classification and Varietal Descriptions of Some American
Potatoes. U. S. D. A. Bui. 176. March 27th, 1915.

CHAPTER IV
POTATO BREEDING

The cultivated potato of to-day has undergone a re-
markable change since its first introduction into Europe
by the Spaniards. Some of this change has been brought
about by better cultivation, but most of it is due to breed-
ing. The tubers of the wild »S. tuberosum were small
and attracted little attention. Heriot, in his report on
Virginia, describes the plant "with roots as large as a
walnut and others much larger ; they grow in damp soil,
many hanging together as if tied on ropes." The potato
as we know it has been developed by means of conscious
and unconscious selection and by hybridization with
other species. The modern potato has not only been
much changed by breeding, but it is now grown in widely
different surroundings which produce various changes
in the tubers.

There are three foundations on which the increased
productivity of crops rests — the enrichment of the land ;
its tillage and care ; and the production of better varie-
ties and strains. The first two are concerned with the
environment of the crop, such as cultivation, fertilization,
freedom from insects, disease and so forth, and the last
with its heredity. We have long given attention to
environment; now we are studying heredity with new
enthusiasm and purpose. One of the "signs of the
47

48 The Potato

times" is the attention that is being given to the practi-
cal breeding of crops. We have learned that good seed
is a necessary accompaniment to high fertility and good
care and also the desirability of different varieties adapted
to varying needs of soil; climate and man.

These wild forms have been taken, in most cases, from
their original habitats and placed under conditions of
soil, temperature and moisture to which they are not
accustomed. Here selection must not only modify the
plants better to meet the wants of man, but they must
become adapted to their new environment. Most
plants are very flexible and finally become adapted to a
variety of conditions. This is evidenced by the very
large number of varieties of which most of our cultivated
plants consist.

Results of careful and systematic breeding are accu-
mulating rapidly with very many kinds of plants. The
results of all this work will probably enable us, even-
tually, to formulate somewhat definite statements as to
how to proceed to secure desired results. Considerable
evidence is already at hand, but on the whole the methods
of breeding are still somewhat empirical.

All of our cultivated plants have come from wild forms.
Man has seen in them possibilities of usefulness, and he
has chosen year after year the ones which better serve
his purpose. This constant selection has in the course of
time produced profound changes in our plants.

IDEALS FOR THE POTATO CROP

Plant-breeding is worthy of the name only as it sets
definite ideals and is able to attain them. Merely to
produce new varieties is of no merit. We must give up

Potato Breeding 49

the production of mere novelties unless the new variety
possesses some property which makes a real contribution
to our present varieties.

It is unfair and dishonest consciously to rename old
varieties under the pretense of producing something new.
Our list of varieties contains many synonyms, and these
should not be consciously increased.

In general, the improvement of our present standard
varieties offers greater opportunities for the increased
efficiency of the new generation of plants than the pro-
duction of entirely new varieties.

Ideals for the perfect potato will change in the different
localities. Certain attributes, however, are universally
desired. These are as follows :

(1) High yield.

(2) Good quality.

(3) Disease-resisting capabilities.

(4) Good keeping qualities.

(5) Good color of flesh and skin.

(6) Skin of desirable texture.

(7) Tubers of good shape.

(8) Shallow eyes, relatively few in number.

(9) Maturing in season common to the variety.

(10) Upright, vigorous plants.

(11) Heavy leaf cuticle.

(12) No tendency to make second growth.

(13) Trueness to type of variety grown.

High yield is essential if the grower expects to continue
raising potatoes for market. In aiming to secure high
yield, however, we should remember that there are many
other factors which determine the marketability and
price of the product. Tubers of inferior quality, size

50 The Potato

and the like are not of great ^•alue even in large quan-
tities.

From the consumer's point of view, quality is highly-
important. The grower would do well to keep his pota-
toes up to standard in this respect. Potatoes intended
for human consumption should have a mealy flesh when
boiled or baked. Up to a certain limit the quality
improves with an increase in starch content. Potatoes
to be used for the production of alcohol need be of no
particular quality from the culinary standpoint.

There are no disease-proof varieties, but some are
more resistant than others. Resistance is more impor-
tant in the East than in the Mississippi Valley.

It is necessary to store potatoes for a long period, to
supply the demands between crops. If the keeping
qualities of a strain are poor, there are fewer potatoes
which can be sold in the spring. In a sense, then, poor
keeping quality is a factor which decreases yield.

The ideal color of skin and flesh will depend largely
upon market preferences. In general a yellow skin and
white flesh are desired. In the South, the red- or pink-
skinned varieties are in favor. Because of the red color
of some weak varieties, growers are likely to be skeptical
of all colored varieties.

The skin may be thick, medium, or thin. Whew grown
in sandy soil, the skin is usually smoother than when
grown in heavy loams. A netted and slightly rough skin
is preferred, many believing that it indicates proper
maturity and good quality.

Flat-round or flat-oval tubers are better than the spher-
ical, as the cortical and outer medullary layers, containing
the starch, are relatively larger. Also a flat tuber bakes
better, because the center is not too far from the outside.

^^^.

Potato Breeding 51

Deep eyes cause waste in peeling. They hold mois-
ture, thereby causing decay in storage. The tuber
should have enough eyes to make good seed, but not so
many as to make peeling difficult.

Early varieties may mature in 70 to 90 days after
planting; second-earlier in 90 to 130 days; and late
varieties may continue to grow for 200 days. It is im-
portant to choose a variety adapted to the locality.

The haulm and leaf are considered more important
than formerly. Large haulms require wider spacing of
plants and greater expense for spraying. Short-haulmed,
upright, heavy-leafed tops are not as susceptible to dis-
ease as the prostrate types. The upright types are more
likely to suffer during very dry spells, however, because
the tops do not prevent the evaporation of moisture from
the soil as do those of the more prone types. Care should
be exercised to select a variety which is well suited to
local conditions and which will grow vigorously. Dif-
ferences in vigor will be noted in different strains of the
same variety.

Leaves with thick cuticles are not as easily penetrated
by disease spores.

When a period of drought is followed by a wet spell,
second growth is likely to begin. The dry weather
checks growth and the tubers begin to mature. Subse-
quent wet weather restarts growth. Such abnormalities
should be discarded in selecting seed.

It is essential that the seed be as represented. None
but experts can tell the different varieties apart, so seed
should be obtained from a reliable source.

The half-tone illustrations in Plates III to VII show
some of the desirable potato forms, and also results in
breeding.

52 The Potato

Use of score-card

A score-card presents in a logically arranged, tabular
form the different factors which make up an ideal potato.
These factors are given relative importance or weight by
means of percentage numbers, the sum of which is 100.
One should make frequent use of a score card to familiar-
ize himself with all details and to compare his product
with the theoretical ideal product, which it describes.

The score-card should be studied so as to establish the
ideal of the desired variety firmly in mind before any
attempt is made at improvement.

■ When breeding a crop, special attention should be paid
to the details. The proper combination of the little and
usually overlooked points makes the perfect crop.

It is important, further, to bear in mind the fact that
a variety which is merely as good as any other in culti-
vation is not worth introducing. It should be better in
some particular than any other in existence. The oper-
ator must know the points of his plant, as an expert stock-
breeder knows the points of an animal, and he must
possess the rare judgment to determine which charac-
ters are most likely to reappear in the offspring. Inas-
much as a person can be an expert in only a few plants,
it follows that he cannot expect satisfactory results in
breeding any species which may chance to come before
him. Persistent and uniform effort, continued over a
series of years, is generally demanded for the production
of really valuable varieties. Thus it often happens that
one man excels all competitors in breeding a particular
class of plants. If the operator — himself an expert
judge of the plant with which he deals — chooses his
seeds with care and discrimination, and then proposes,

Plate V. — Typical early and late potatoes. Top, Irish Cobbler (early).
Bottom, Rural New Yorker (late).

Potato Breeding

53

if need be, to follow up his work generation after genera-
tion by means of selection, the work becomes plant-
breeding of the highest type.

First of all, therefore, the operator must know what he
is likely to secure, and what will probably be worth se-
curing. ]Most persons, however, begin at the other end of
the problem, — they get what they can, and then let the
public judge whether the effort has been worth the while.

The following score-card has been adopted by the
New York State Potato Association :

Potato Score-card

Conformity to

Varietal Type

100 Points

Conformity to

Market Demand

100 Points

Perfect

Perfect

Uniformity

Blemishes and disease . . .

Shape

Size

Quality of flesh

Depth and frequency of eyes .
Color and texture of skin . .

20
15

15
10
10
15
15

20
20
15
15
10
10
10

100

100

This score-card is arranged with the idea of empha-
sizing the more important characteristics to be con-
sidered in selecting potatoes both true to varietal type
and in accordance with market demands. These two
sets of qualifications are in many cases quite distinct. It
is, therefore, true that the variety which fulfills both of
these requirements is the one that scores highest and of
which production should be encouraged.

54 The Potato

Uniformity. — Exhibit should be uniform in all phys-
ical characteristics.

Blemishes and disease. — Should be no evidence of
blight, rot, grubs, rhizoctonia, sunburn, or injury from
rough handling.

Shape. — Should be typical of the variety. Market
demands a moderately oval-flat or round-flat shape.

Size. — Should be typical of the variety. Market
demands a medium-sized potato.

Quality of flesh. — Should be true of the variety.
Market requires a fine-textured flesh of light color, free
from excess moisture and from hollow or dark spots.

Depth and frequency of eyes. — Should be typical of the
variety. Market demands few and shallow eyes.

Color and texture of skill. — Should be typical of the
variety. Market demands a thin, smooth skin. White-
skinned varieties are preferable in most markets.

POSSIBILITIES OF IMPROVING THE POTATO

Even though the potato has been in cultivation for
centuries, further improvement is by no means impos-
sible. It responds very quickly to breeding. Most
varieties are very impure and contain various types.
The first task of the breeder is to become thoroughly
acquainted with his plants so as to discard the poor
plants and save the good ones for future planting. If
this is done for a few years, the average yield of the
crop and its uniformity will be greatly benefited.

The hill selection of potatoes is not generally practiced
and as a consequence the varieties soon deteriorate and run
out. This deterioration could be easily prevented by pay-
ing careful attention to planting seed from the best hills.

Potato Breeding 55

It must not be forgotten that potatoes are now grown
in regions where the cHmate is not entirely congenial
to them. This constant action of a somewhat mifavor-
able climate will also cause them to degenerate if not
counteracted by seed selection.

Careful experiments have been conducted with pota-
toes in which the offspring of different tubers are planted
and recorded separately. Many of these progenies seem
to degenerate completely, indicating that some degen-
erative factor, still unknown, is constantly at work.
This deterioration is partially due to disease, without
doubt, but some of it also is of a physiological nature.

The yields of any field or the average yields of any
locality or of an entire state are far below what they
should be. This is due to two causes : the conditions
surrounding the crop have not been the best — perhaps
insufficient food supply or water or poor soil; and sec-
ondly, the absence of seed selection has produced a poor
stand of plants, many of which probably give low yields.
By proper attention to fertilization, spraying and seed
selection, the yield may often be doubled or trebled.
Perhaps we can never expect the high yields to the acre
obtained in Europe because of our hot dry climate
(see Chapter I),

If seed selection becomes generally practiced, with
its accompanying increase in yields, vast consequences
may be looked for. If all of the hills on an acre of pota-
toes planted in the ordinary manner weigh one-half a
pound, there will be a yield of 78 bushels to the acre.
A half-pound hill, however, is very small. One ordinary-
sized tuber will weigh more than that. If, by means of
breeding, the average yield to a hill is increased to one,
two or three pounds, which is not at all impossible, the

56

The Potato

yields to the acre will be increased to 156, 312 and 468
bushels respectively. If this reasoning were applied to
all of the potato fields in the United States, the result
would be almost unbelievable. Burbank has made the
conservative estimate that if one tuber were added to each
hill, the total resulting increase in the United States
would be 21,000,000 bushels yearly.

The following table gives the yields to the acre from
hills of certain weights. It is assumed that the hills
were 18 inches apart in the rows and the latter were 3 feet
apart. This rate of planting gives 9372 hills on an acre :

Table IX

Yield to the Hill

Pekpect Stand

90 Per Cent Stand

Pvunda

Bushels to the Acre

Bushels to the Acre

.5

78.1

70.29

1.0

156.2

140.58

1.5

2.34.3

210.87

2.0

312.4

281.16

2.5

390.5

351.45

3.0

468.6

421.74

3.5

546.7

492.03

4.0

624.8

562.32

METHODS OF IMPROVEMENT

Plants are improved in three ways : first, by simple
selection, that is, breeding from the best, the object
being to improve the present varieties rather than the
production of new ones; second, to conduct extensive
plantings for the purpose of discovering some unusually
good individuals or mutants, which may become the
foundation of improved varieties and which subsequently

ffl

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-m

^

1^31^3^^

^

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■Tt -

Plate VI. — Breeding — Each group of four plates represents the
progeny of a tuber ; and each plate is the produce of a single hill.

Potato Breeding 57

require little else of the grower than their multiplication ;
and third, by crossing plants to combine the best qualities
of two or more parents in a new and improved variety.

Improvement of the 'potato by selection

The principal method of improving the potato is by
bud-selection. Potato hills are very variable, and im-
provement is made by planting tubers from the best
hills. Many of these apparent improvements may be
due to some advantage in growth, such as increased fer-
tility, more light or moisture and so forth. Of course,
this increase is only transitory, and not being inherited,
produces no permanent advancement.

The potato, however, presents variations which are
inherited. These are of two kinds, — smaller differences
whose inheritance produces a gradual change, and large dif-
ferences or so-called "bud-sports" or bud-mutants which
immediately become the starting point of new varieties.

Potatoes differ from most farm crops in their manner
of reproduction. They are propagated vegetatively
without the intervention of a sexual process like corn
or wheat. Each hill of potatoes comes from one tuber or
a part of a tuber which was the product of one bud of the
mother plant. Hence the entire hill becomes a unit, and
hill selection is, in reality, bud-selection. Single tubers
cannot be said to be units from the breeder's standpoint.
Therefore, it is of supreme importance to take into ac-
count the yield of an entire hill and not the presence in
it of two or three large tubers resulting in low total yield
for the hill.

So far as man is concerned, the origin of the initial
variation is largely chance, but this start or variation

58 The Potato

once given, he has the power, in most cases, to perpetuate
it and to modify its characters. There are two very
different factors or problems in the origination of potato
varieties by selection, — the production of the first de-
parture or variation, and the subsequent breeding of it.

It is apparent that the very first effort on the part of
the potato-breeder must be to secure individual differ-
ences. If the plants which he grows are very much alike,
there w^ill be very little hope of obtaining new varieties.
He should, if possible, cause his plants to vary. This
initial variation may usually be induced by changing the
conditions in which the plant has habitually gro\\ai, as
a change of seed, change of soil, tillage, varying the food
supply, crossing and the like. As a matter of fact, how-
ever, nearly all plants which have been long cultivated,
like the potato, are already sufficiently variable to afford
a starting point for breeding. The grower should have
a vivid mental picture of the variety which he desires to
obtain; then he should choose those hills which most
nearly meet that ideal.

Experimental breeding has demonstrated that the
different varieties of farm and garden plants, as we ordi-
narily know them, are not entirely homogeneous and
uniform, but are made up of smaller groups now known
as "pure lines." It is ordinarily understood that a pure
line is the progeny of a self-fertilized indi\idual, that is,
one in which all effects of crossing have been eliminated
by constant self-fertilization. In potatoes which are
ordinarily propagated asexually, a pure tuber line would
be the progeny of a single tuber.

Experiments seem to demonstrate that the group of
individuals known as a pure line vary much less than the
variety as a whole, and that selection of the best indi-

Potato Breeding 59

viduals within a pure line has httle, if any, effect in raising
the average of the Hne. Tliis has not been proved, by any
means, but the indications are that only a very slight ad-
vance is made by continued selection after a pure line has
been reached, unless an exceptionally good individual
should arise whose progeny would constitute a new and
better line.

It will now be seen that the first work in improving
potatoes by selection is to determine the best tuber lines
and plant them for seed. This necessitates carrying out
a system of breeding whereby individual tubers must
be planted separately and properly labeled and their prog-
eny kept separate for a few years to determine whether
or not the desirable plants transmit their qualities to fu-
ture generations (see Plate VI). This is known as "pedi-
gree breeding." Myers gives the following table to show
variation in the yielding capacity of different tubers.
Each unit is the product of a different parental tuber :

Table X

Unit Yield in Bushels

No. TO THE Acre

1 110

2 220

3 220

4 230

5 280

6 320

7 240

8 230

9 230

10 130

11 210

12 70

13 190

14 190

15 25

16 270

60

The Potato

If the first work of breeding consists of separating out
pure lines and if there is very slow progress within these
lines, it is obvious that the choice of individuals for
planting the first few years is all-important. As large
fields as possible should be grown to give opportunity
for all of the best plants to appear.

Fio. 8. Potato yields. Diagrams showing variation in yield of in-
dividual rows of potatoes grown on special seed plots in 1909. (Carman
No. 1, by R. H. Crosby, Markham, Ont.)

Until recently, the method of selection has been to
choose from the potato bins in the spring the requisite
amount of seed, using tubers having the desired size and
shape but without knowledge of whether they came from
high yielding strains or not. This method of choosing
seed from year to year, using merely the best tubers

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Plate VII. — Tubers with histories. Upper, influence of unfavorable
growing season, showing the second-growth tubers on the right compared
with normal uniform tubers on the left. Lower, Breeding — the im-
munity and susceptibility of two tuber progenies.

Potato Breeding

61

without a knowledge of their ancestry or obtaining a
test of their producing power, is known as "mass-selec-
tion." This method will inevitably lead to improvement

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7

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Fig. 9. Continuation of Fig. 8.

because the very poor hills will not produce good tubers,
and hence will be eliminated. But the improvement is a
very slow one. In employing this method of mass selec-

62 The Potato

tion, growers were working blindly without knowing how
or when or even whether they were going to reach a sta-
bility of type. On the other hand the method of pedi-
greed culture or "individual selection" eliminated the
fear of failure because of the appearance of the hitherto
unsurmountable variations.

Plants which have any desired characteristics in com-
mon may differ widely in their ability to transmit these
characters. It is generally impossible for the cultivator
to determine, from the appearance of any given progeny,
the most invariable and the most like its parent ; but it
may be said those individuals which grow up in the most
usual or normal environments are most likely to perpet-
uate themselves. A very unusual condition, as of soil,
moisture or exposure, is not easily imitated when provid-
ing for the succeeding generation, and a return to normal
conditions of environment may be expected to be followed
by a more or less complete return to normal attributes
on the part of the plant. If the same variation, therefore,
were to occur in plants growing under widely different
conditions, the operator who wishes to preserve the new
form should take particular care to select his tubers from
those individuals which seem to have been least influenced
by the immediate conditions in which they were grown.

The method of individual selection or pedigree breed-
ing is now universally accepted by the best • breeders.
In potato-breeding it is known as the "tuber-unit"
method, that is, the progenies of individual tubers are
tested for a number of years to determine the best pure
lines which are constant from year to year.

One of the first and best methods of breeding potatoes
by the tuber-unit or pedigree plan has been devised by
H. J. Webber. This method is so satisfactory, when
properly carried out, that it is given here in detail :

Potato Breeding 63

Selection of foundation stock of potatoes. — Probably no crop
generally grown is more influenced by environment than the potato.
The experience of growers indicates that a variety found to be the
best suited to local conditions on one farm may not prove to be the
variety best suited to the conditions existing on an adjoining farm.
It thus becomes desirable for any farmer who is growing potatoes
extensively to test varieties sufficiently to determine which is the
variety best suited to the local conditions concerned. This ordi-
narily does not require an extensive test as the experience of growers
in a region has usually shown the general superiority of a com-
paratively few varieties, and a test can thus be limited to these varie-
ties which in general are known to be the best. The WTiter would
not urge this test of varieties, if it were not very important to begin
any breeding work with the best variety available. Breeding work
requires so much attention that it does not pay to start with an in-
ferior variety. The first effort of any one contemplating breeding
with potatoes is thus to determine the best foundation stock to use
for the selection work. If the grower has had extensive experience
in growing potatoes and has determined that a certain variety
gives the best results under his conditions, he is in a position to start
the selection without a further test of varieties.

Growing potatoes for selection. — The influence of the number of
eyes and size of piece planted as seed has so much to do with the
yield of the liill that fields planted in the ordinary way are very
poorly adapted to begin the work of selection. It is of primary im-
portance that the first selections be of the very highest type obtain-
able, as it is a common experience that the first selection is the most
important. Too much attention cannot be given therefore to the
first selection. The writer would thus urge the following method
as one of the most satisfactory to be pursued :

(1) Examine a large number of tubers of the variety selected as
the foundation stock and decide on the most desirable shape and
type of tuber. In general a moderately large tuber, which is oblong
or somewhat cylindrical in shape and oblong in cross section, is
considered most desirable. A spherical tuber if sufficiently large
to be desirable is so thick that in cooking the outside is likely to
become overdone before the interior is properly cooked. A tuber
with shallow eyes, netted surface and white color is also usually
preferred. Probably the best-sized potato for general use is one
weighing seven to eight ounces. A potato of this size does not have

64 The Potato

to be cut when served, as a single tuber is about the right size to an
individual. Again this sized tuber is well fitted for cooking and it is
small enough so that the interior will cook nearly as quickly as the
exterior. Probably the most desirable shape is when the tuber has
a major axis or length of three and one-half inches to four inches, with
a width of possibly three to three and one-fourth inches, and a thick-
ness of two to two and one-fourth inches. In a tuber of this shape
the center of the potato at any point is only about one inch from the
exterior.

(2) When the ideal character and size have been determined,
examine a large number of tubers and pick out a thousand or more
having this size, shape and general character. This is work that
can be done in the late fall and winter when there is no rush of other
farm work, and time should be taken to secure a considerable number
of these tubers of the same character. These are to be used for
planting the selection plot, and the number selected should correspond
to the size of the plot which it is desired to plant, four hills being
planted with each tuber. There should certainly not be less than one
thousand, and a much larger number is more desirable. The pro-
spective breeder should remember that success in breeding work de-
pends upon selecting the one individual that gives the very highest
yield possible under the conditions, and the larger the number of
individuals examined the more likely is he to discover the one produc-
ing the maximum yield which will give a valuable new strain. There
is no loss in growing this selection plot aside from the greater amount
of time required for the digging, so that one should grow a consider-
able number of plants.

(3) The planting should be arranged in such a way as to secure
a test of the productivity of each tuber. To do this the following
method may be recommended. Cut each tuber into four uniform
sized pieces, making each cut longitudinally so that each piece
will contain an equal proportion of the basal end and the apical end
of the tuber. Plant four hills with each tuber, one piece in the hill.
These should be planted consecutively in each row beginning at one
end, so that starting at that end the first foiu- hills will be from one
tuber, the second foiu- from another and so on throughout the
length of the row. The object in planting this way is that four hills
can be dug together and the total product weighed to obtain a meas-
ure of the productivity of the seed tuber planted. Probably the
best way to plant these is to drop the selected tubers one to each

Potato Breeding 65

four liills and then go over the row and cut each tuber and plant
its quota of four hills. The hills in the row should be planted some-
what farther apart than in ordinary planting, probably 20 to 24
inches. If this is not done, a somewhat greater distance than ordinary
should be left between each two four-hill tuber-units. The writer
would advise that one hill be left unplanted between each two four-
hill units. It would doubtless be convenient and desirable to have
the plants in rows both ways to facilitate digging. For this selec-
tion-plot of potatoes, choose a field of moderately good fertility and
as uniform throughout in soil as it is possible to obtain.

(4) Manm"e and cultivate the plot of potatoes grown for selec-
tion just the same as you do your ordinary crop.

How to make the selection of potatoes — field examination. — A
careful examination of the selection field should be made as the
vines begin to matiu-e and while they are yet green. This examina-
tion should include observations on diseases and vigor of the tops.
If there are any marked differences apparent between the different
four-hill units, those with the best-appearing, most healthy tops
should be marked by small stakes which can be stuck in the ground
beside the hills. This field examination, while important in careful
work, probably could be omitted without very great loss, as after all
the yield is tlie primary character.

Digging the selection field. — The digging of the field grown for
selection purposes requires considerable care, and here hard work is
necessary. Dig each four-hill unit grown from the same tuber sei)a-
rately, being careful to get all of the product, and avoid cutting or
injm-ing the tubers if possible. Carefully place the product of each
foiu"-hill tuber-unit together at one side of the row, and if it is a tuber-
unit marked with a stake in the field examination, keep the stake
with the product of the unit. A good way to dig in order to avoid
getting the hills of different tuber-units mixed is to dig across the
field, in a direction at right angles to the direction the rows were
planted. First dig the four hills of the first tuber planted in the first
row, then the four from the first tuber in the second row, then the
same in the third row, fourth row, etc., tlirough the field. Next
dig the foiu" hills from the second tuber planted in the first row, then
the four from the second tuber in the second row, etc. By this
method of digging, especially if the hills are rowed both wa^'s, there
will be little danger of mixing the product of the four-hill units.

Making the selections. — The problem after digging is to select

66 The Potato

fifty to one hundred of the best tuber-units, — best, that is, in jneld,
uniformity of product, color, shape, etc. After the potatoes are dug
and the product of each tuber-unit is laid out separately, the real
work of selection begins. The following are the important steps in
this process :

(1) Go over the field and study the tuber-units in a gross way
until you have well in mind the variations in yield and the gen-
eral uniformity of the tubers in the various tuber-units. Re-
member that the total yield is not the only important character.
What one wants is to discover those tuber-units which have the
largest yield of good merchantable potatoes of the best shape and
appearance. Size up the field as a whole with reference to these
characters.

(2) Go over each row carefully and throw out all of those tuber-
units which can be clearly seen to be inferior ; these may be thrown
together and placed with the general crop of potatoes. For the
interest of the grower, however, it would be well to weigh the prod-
uct from some of the light-yielding tuber-units and preserve the
figures for the sake of showing the extent of variations occurring.
By this first discarding process the number of tuber-units will proba-
bly have been reduced to two or three hundred. It is very prob-
able that in some cases one or more of the hills of a four-hill tuber-
unit will not grow. In such cases the tuber-unit will have to be
judged in proportion to the number of hills actually grown.

(3) Now provide yourself with scales of some handy pattern
like the ordinary counter scales used by grocers, with which the
product of each tuber-unit can be easily and quickly weighed. A
satisfactory scale should weigh accurately to at least a half ounce.
Weigh the product of the remaining tuber-units, examine the tubers
more carefully as to their character and uniformity of size in the
tuber-unit and select about fifty of the best units. These fifty
units should naturally be from those marked as having good healthy
vines in the first examination before digging, unless all of the vines
at that time were in fairly good condition. In making these final
selections, if some hills in the tuber-unit are missing, the comparative
yield can be easily calculated. If one hill is missing, a comparative
yield for four hills is obtained by increasing the weight from the three
hills by one-third. If two hills are missing, a comparative yield for
four hills would be double that obtained from the two hills. If more
than two hills are missing, discard the unit entirely.

Potato Breeding 67

The product of the tuber-units selected should then be placed in
paper bags, the product of one tuber-unit only being placed in a bag.
A good bag for the purpose is the 12 or 16 pound manila paper bag
used by grocers. The 12-pound paper bags of good quality should
cost only about 40 cents per hundred. If the 12-pound paper bag
is too small, use a 16-pound bag. In your notebook record under
the number of each tuber-unit, the number of large, medium-sized,
and small tubers and the total weight of the product. The bags
containing the seed should then be placed in suitable storage where
they will not be torn or the tubers mixed. The tubers from the
best discarded tuber-units should be retained to plant the general
crop the next year.

If at digging time the grower is crowded with work and wishes
to save time, the two or three hundred tuber-units retained after the
first gross selection (see paragraph 2 above) could be placed in paper
bags and the more careful examination and weighing of the product
delayed until some convenient time during the winter when the final
selection could be made.

Selecting seed for the second year's planting. — Some time during
the winter or at any convenient period before planting time care-
fully examine the product of each select tuber-unit and pick out the
ten best tubers of each as judged by the ideal standard of a good tuber
which has been taken as the type of the selection. The ten best of
each retain in the numbered sacks for planting and discard the re-
maining tubers.

Second year's planting. — In the further handling of the selec-
tions made the first year the planting the second year must be ar-
ranged in order to test the productive power of each of the fifty
select tuber-units. Plant each tuber-unit in a row by itself by the
same method used in planting the first year's crop (see p. 64). That
is, plant four hills with each tuber, cutting the tuber longitudinally
into four equal-sized quarters, making each cut from base to apex
of the tuber. As ten select tubers were retained from each tuber-
unit this will make forty hills per row, and if fifty tuber-units were
selected, there will be 500 tubers to plant, which will make a total
of 2000 hills in the breeding-plot. The land used for this breeding-
plot should be carefully chosen for uniformity, as variations in the
land will modify the comparative yield and are likely to render the
results untrustworthy. Number each row of forty hills with the
number given the tuber-unit of the preceding year. It is desirable

68 The Potato

for comparison to plant about every tenth row with unselected
seed of the same variety, cut and planted in the same way, but
without reference to keeping each tuber separate. The production
of these check-rows will show whether progress is being made in the
selection.

Cultivate the breeding plot and treat it otherwise just as an ordi-
nary crop is treated.

Making the second year's selection. — Wlien the breeding plot
ncars maturity, the individuals should be examined and either the
best and healthiest vines marked or, if easier, the diseased vines
showing weakness marked, so that they can be discarded later.
Then dig each tuber-unit as in the preceding year, placing the tubers
from each four-hills together at the side of the row. Each unit should
then be weighed and the number of large, medium and small sized
tubers recorded. This will enable the breeder to determine which of
the original fifty tuber-units selected in the first year has given the
largest average yield in the ten tuber-units or forty-hill test, and
this is the primary test of the value of the original selection. Follow-
ing the same method as used the first year, select from the breeding-
plot the fifty best tuber-units, and preserve the tubers of each unit
separately in a paper bag. The majority of the selection in this
year should naturally be made from those rows which have given
the highest yield. Number the tuber-units selected in this second
generation 1-1, 1-2, 1-3, etc., and 2-1,2-2, etc. In such hyphenated
numbers the first figure refers to the number of the tuber-unit se-
lected the first year, and the second number, that following the
hyphen, refers to the number of tuber-units elected from this prog-
eny the second year. Thus in the case of 2-2, the first 2 indicates
that it was the second tuber-unit selected in the second year from
progeny of unit No. 2 of the first year's crop. In the third year the
numbers can be extended by the same principle, the tuber-units
selected from progeny 2-2 in the third year being numbered 2-2-1,
2-2-2, 2-2-3, etc. These numbers can be placed on the bags and
notes on weight of yield, number of tubers per unit, etc., recorded
under the same number.

All of the good tubers from the remaining tuber-units of the
breeding-[)lot not selected should be retained for planting a multi-
plication-plot the third year, which should furnish sufficient seed for
planting the general crop for the fourth year.

At some convenient period before planting time, as in the pre-

Potato Breeding 69

ceding year, go over the product of each select tiiber-unit and pick
out the ten best tubers of each for the next year's planting.

Continuing selections in third year. — In the third year, the fifty
selections of heavy yielding tuber-units should be planted by the
same method used the second year, at least forty hills of each selec-
tion being planted. The row from each unit should be plainly la-
beled or otherwise marked to avoid mixing the pedigree. Treat this
breeding-plot as described for the breeding-plot in the second year,
weigh up the product of each four-hill tuber-unit in the same way to
determine which unit of the second year's selection has transmitted
in greatest degree the tendency to yield heavily. Finally, select
again the best fifty tuber-units to continue the breeding, and retain
the good tubers of discarded units to plant a multiplication in the
fourth year.

In the third year, a multiplication-plot should be planted with the
good tubers from the discarded tuber-units of the breeding plot of
the second year. In planting this plot the grower can use any
method of cutting and planting the tubers which he thinks most
desirable. This plot should give enough seed to plant a fairly large
plot in the fourth year.

Continuing selections in fourth and succeeding years. — In the
fourth and succeeding years the selection should be conducted by
the same plan as outlined above. When this system is well under
way, it will be seen that each year the breeder is growing a small
breeding-plot, a large multiplication-plot for seed and a general
crop.

Further considerations. — As the selection progresses many of the
strains from the original fifty tuber-units will be entirely discarded.
The breeder must be continually watching for the appearance of a
heavy yielding strain, and if such a strain is discovered, all of the
further selections should be made from this strain.

In advocating the selection of but fifty tuber-units and the
planting of ten tubers only from each select unit the writer has
had in mind the reduction of the work to a comparatively simple
plan which would be better to handle larger numbers if the grower
is so situated that he can take the time for it. It is, however, better
to use comparatively small numbers carefully than to attempt to.
handle large munbers and find the work too extensive.

70 The Potato

Another method of selection has been suggested which
is simpler than Webber's method, probably not as satis-
factory, but which has been found very useful by many
growers. It consists of planting, growing and digging
the tubers the first year as previously suggested, but in-
stead of weighing the hills and keeping them separate for
further tests, they are chosen by means of counting in-
stead of weighing. If the season has been an average
one, the hills which have six or more good tubers are
saved for future planting. Perhaps it may be necessary
to use five as a standard of selection or even seven may be
used if the crop is good. There is no attempt at pedi-
gree breeding by keeping the different strains separate.
All hills meeting the established standard are thrown
together and saved for seed. The next year these are
planted and grown like the rest of the field. In the fall
they are dug by hand and again the best hills by count
are saved for seed. This method will gradually elimin-
ate the poor strains and raise the average yield of the
crop very rapidly.

Spillman says : " A potato grower in Michigan some
years ago began the practice of digging by hand enough
potatoes for seed and saving only those hills that had six
or more merchantable tubers and no small tubers. When
he first began this practice, only sixteen hills out of each
hundred dug came up to his standard, but after he had
continued this practice for five years the number of such
hills had risen to seventy in a hundred."

Another similar instance is found in some unpublished
results secured by Dodge of the office of Farm Man-
agement, who for several years has been teaching some
New England potato-growers how to select seed potatoes.
The method adopted is to save for seed those hills that

Potato Breeding 71

produce six or more merchantable tubers. This experi-
ment has extended over three years. The first year,
from 7 per cent to 8 per cent of hills were found that met
the requirements ; the second year from 17 per cent to
20 per cent. This season the number of hills which have
produced six or more merchantable tubers has risen to
24 per cent to 27 per cent.

Whenever pure lines or strains or varieties of potatoes
are compared, every effort should be made to eliminate
soil differences or other factors of environment, so that a
direct test of the heredity only can be made. Potatoes
are so easily influenced by environment that real heredi-
tary differences are often covered up. Absolute uni-
formity in time of planting, methods of culture, spraying
and so forth are essential. The seed pieces should be as
nearly the same weight as possible. Arthur says, " What-
ever increases rate of growth at the beginning, increases
yield."

If tuber-units are being compared, they should be
planted in duplicate or preferably in triplicate in differ-
ent parts of the field and their production averaged.

If single high-producing hills are saved for the next
year's planting, one should make sure that they did not
come from some highly fertilized part of the field. Pref-
erably they should be chosen from the poorer parts of the
field when their production may be high in spite of their
environment, the real test of heredity.

Zavitz, of the Ontario Experiment Station, selected
the best hills of seven varieties of potatoes for a period
of sixteen years. During the first four-year period
the average yield was 120 bushels. During the three
succeeding periods of four years each, as a result of
selection, the average yields were increased to 216, 218

72

The Potato

and 249 bushels. Within the sixteen-year period, the
methods of culture were kept practically the same
and the result is, therefore, attributed to the result of
selection.

Waid has conducted at the Ohio Experiment Station
a series of experiments for the purpose of securing data
to throw more light on the question of the value of hill
selection in potatoes. In this work, starting with the
same original lot of tubers, three strains were grown
as follows : (1) seed from high-yielding hills ; (2) seed
from low-yielding hills ; (3) unselected seed. The fol-
lowing table gives the summary of the results that were
obtained from high-yielding hills and from low-yielding
hills:

Table XI. — Summary of Results from Use of Seed Po-
tatoes FROM High-yielding Hills and from Low-yield-
ing Hills. (Variety, Carman No. 3)

Source of Seed

Yield of 100 Hills

Number op Tubers in
100 Hills

Total
1904

Total
1905

Total
1906

Average
1904-5-6

Total
1904

Total
1905

Total
1906

Average
1904-5-6

High-yielding hills .
Cheek rows . . .
Low-yielding hills .

Lhs.

125
115
84

Lbs.

173

136

75

Lbs.

116
79
61

Lhs.

138

110

73

781
713
566

865
630
546

676
479
364

774

607
492

Running out of varieties

Potatoes are grown in many parts of the world where
the climate and soil are very different from that of their
native home. Also all of our varieties which have been
developed as a result of breeding give yields far in excess

Potato Breeding 73

of the wild forms. The stress of uncongenial environment
and hirge production of tubers causes most varieties to lose
this abnormal (from the standpoint of the plant) produc-
ing power and to decline unless selection is constantly-
practiced. Disease may be partially responsible for this
degeneration.

Running out of varieties is often caused by repeated
planting of culls and poorer specimens while the best are
sent to market.

Newman ^ says, that in vSweden there is a potato known
as the Dala, which is said to have been introduced about
150 years ago and is still one of their best sorts. The
opinion held at Svalof is that there is no period of old age
in a variety of potatoes ; that where suitable sorts are
used, and where suitable tubers of these sorts are used for
seed purposes each year, the planting of the variety may
be maintained indefinitely under all favorable conditions
of soil and climate. The main considerations are mainte-
nance of vigor and control of disease, and this implies
careful selection of seed tubers, careful cultivation and
spraying and rotation of crops. Special emphasis is
laid upon the latter point.

Orton sa}^s : " The same system of seed selection and
treatment and crop rotation that will free the potato
fields of wilt, leaf-roll, and curly-dwarf will at the same
time not only bring under control the blackleg and some
other diseases but will insure the maintenance of the
strains cultivated in their most vigorous and productive
condition and be free from objectionable mixtures with
other varieties."

The following statement from Fruwirth is representa-

• " Plant Breeding in Scandinavia." Canadian Seed Growers Associa-
tion, Ottawa (1912).

74 The Potato

tive of the opinion held by most of the European experi-
menters. "And the real degeneration, an ageing of a
variety, which has been under uniformly favorable condi-
tions and of which good seed is used has not been pro\'ed
and is improbable."

Varieties seem to differ in their staying qualities.
Some have held up for 50 to 60 years, while others have
passed out quickly. The old Peachblow variety which
was widely grown forty years ago has largely run out
now except in certain localities like the Carbondale region,
where it has been given careful selection and is better
to-day than ever before.

Another reason ascribed is that long-continued bud
propagation results in an inner physiological weakening.
It is difficult to see, however, how prolonged asexual
propagation affects stocks injuriously.

What appears to be the running out of a variety may,
in some instances, be due to a change in market demands
and the varieties disappearing which do not meet these
demands. For example, the old long Burbank has
given place to the more round varieties such as the Rural,
and the Blue Victor has been replaced by white varieties
and has now practically gone out of existence. Fru-
wirth believes that a lack of adaptation to local condi-
tions results in a degeneration of certain varieties. Poor
attention to the selection of seed tubers is also suggested
as a cause of deterioration. Fruwirth summarizes the
opinions of a number of German experimenters in sup-
port of these two views.

East points out that perhaps the potato requires
frequent crossing to keep up the vigor, and that possibly
continual propagation by asexual methods causes a loss
of heterozygosis.

Potato Breeding lb

Certain plant characters are often associated together.
In breeding practice a knowledge of these associations
is often valuable. If easily observable physical char-
acters, such as color of flower or texture of skin, are asso-
ciated with chemical composition, which is less easily
detected, the appearance of the former is a valuable
index to the existence of the latter. It has been often
observed that there is a certain shade of green in the
leaves which is correlated with vigor and high produc-
tivity. If the leaves are too light green, few tubers will
be produced, or if too dark, the yield is again small or a
large number of small tubers will be found, due to late
maturity or possibly to disease. Correlations are es-
pecially valuable when they enable one to select out good
plants in a young stage, or when they save the trouble of
making elaborate chemical analysis. Only a few defi-
nite correlations have been discovered in the potato.
East reports nearly all of these in Illinois Bulletin 127,

There appears to be a positive correlation between
yield and the following : flat shape of tuber, number of
stalks to the plant and length of the growing season.
With a heavy setting of seed berries, we may usually
expect a light production of tubers. No correlation has
yet been found between color of the tuber and yield.

Fischer of Germany (reported by East) says that round-
flat tubers tend to produce plants which are rather com-
pact in habit. Cylindrical tubers produce large, scraggly
plants.

Round-flat tubers are richest in starch. Quality is
said to improve directly with an increase in starch con-
tent up to a certain point. An excessive amount of
starch causes the tuber to be coarse and woody. A
netted skin is usually associated with high quality.

76 TJw Potato

No correlation has been discovered between color of
tubers and color in the stems and flowers.

In certain varieties there seems to be a coupling of
characters and what appears to be a close correlation.
This same association, however, may not hold for any
other variety. As East points out, we ought to have a
good understanding of the life history of different varie-
ties before we draw definite conclusions as to the correla-
tion of characters.

Appearance of bud sports

Occasionally, a single bud, or group of buds, on a tuber
will give rise to a plant distinctly unlike any others of
the variety. This is known as bud-sporting. Just
what causes this unusual behavior we can only speculate
upon. No definite cause is known.

Darwin reports three cases of bud sporting. A tuber of
the purple variety "Forty-fold" had a single eye that was
white. This when planted gave rise to a white variety.
The same purple variety in another instance produced a
white tuber which bred true. The white variety " Kemp "
sported to give the red "Taylor's Forty-fold."

Fruwirth reports a case where a yellow tuber gave
rise to a violet-skinned form. Examples of this sort
are rather numerous.

Such bud sporting is not limited to characters of the
tuber. Many believe that habit of vine, vigor, produc-
tiveness and other characters may be affected by sporting
of the tuber buds.

By carefully examining the hills of the breeding plot
at digging time, any valuable bud sports can be selected
out for further propagation.

Potato Breeding 77

Improvement by hyhridization

It is hardly advisable for the practical potato-grower
to attempt an extensive improvement of his crop by
hybridization. While the method has yielded good
results in some cases, there are many difficulties in the
way and the results are very uncertain. The major
portion of a farmer's potato breeding plot should be
given over to tuber-unit tests. If the grower feels that
he can spare the time and is willing to risk a failure in
his enterprise, it would be of interest and possibly of
profit to attempt a few crosses between his better strains.
Otherwise this method should be left to the experiment
station worker, who has the time to make the large
number of manipulations necessary, and who can devote
large areas to the growing of the seedlings.

Plants are hybridized primarily to increase their varia-
bility and to furnish more material on which to practice
selection. In the light of modern mendelian studies,
we have come to look upon hybrids as recombinations
of characters present in the parents. Care should be
exercised to choose parents having as many desirable
characters as possible. Subsequent selections should
preserve those plants which combine the largest number
of desirable qualities from both parents. Hybridiza-
tion usually increases vigor and is often useful in restor-
ing this characteristic in weakened strains.

There are certain conditions which make the successful
hybridization of potatoes very difficult. In the first
place, there is a strong tendency in most varieties not to
set seed. In such varieties, the flowers drop off shortly
after pollination. This necessitates making a great
many pollinations with the hope that a few plants will

78 The Potato

set seed. Salaman ^ estimates that only 5 per cent of
his crosses set seed. East - found it difficult to get a
good setting of seed in very dry seasons.

In some cases, persistent attempts have finally resulted
in a successful cross where at first it seemed impossible.
A second drawback is the scarcity of pollen. Many
varieties produce little or no pollen and have to be crossed
if we are to get sexually produced seed from them. Also,
some plants produce yellow pollen which is sterile and
does not function. Other varieties rarely, if ever, flower.

Most varieties of potatoes are already hybrid and
when seed from them is sown, the type breaks up into
many elementary forms, most of which are of no value
to the grower. This adds another difficulty to those
mentioned above. Each variety which is crossed trans-
mits a number of undesirable, latent characters which
come out in the hybrids. Often the seedlings from a
cross will show so many of the traits of the wild potato
that none of them is worthy of further attention. Se-
curing a valuable new variety from a cross seems in this
case to be largely a matter of chance. There is an ele-
ment of uncertainty in the work, which is not encoun-
tered with most crops.

The potato flower consists of a rotate corolla of white,
lilac or purple petals, five green sepals, five anthers and
a single pistil. The style projects up through the "cone"
formed by the closely adhering anthers. The anthers
open at the tips and give out a small amount of pollen.
In the day time, the flower is in an erect position, and it is
impossible for pollination to take place. At night, how-
ever, the flower bends over and some of the pollen can fall

1 Journ. Gcii., Vol. 1, pp. 7-46.

2 Illinois Bui. 127.

Potato Breeding 79

down on to the stigma. The flowers open in the morn-
ing and close late in the afternoon. Fruwirth says that
potato flowers usually give off pollen the second day
after opening and wilt the third or fourth day. The
period of flowering for a single plant is between 28 and
33 days. It seems to be a general opinion that the potato
flowers are only rarely visited by insects, and that wind,
also, plays little part in the pollination of the blossoms.

The first thing to be done in hybridizing plants is to
decide on a definite ideal. We then choose our parent
plants with reference to this imaginary type, trying to
obtain plants which have as many as possible of the
qualities sought in the new form.

Generally speaking, it makes no difference which
variety we use as male and which as female parent. A
great deal will depend on the nature of the varieties
themselves. Obviously, we must pick for male parent a
variety which bears at least a moderate amount of pollen.

It is well to keep in mind a few general principles of
hybridization as we proceed. First, the plant to be
used as female parent should be emasculated to prevent
its setting seed by its own pollen. This must be done
before the anthers have matured. Secondly, it is safest to
bag flowers to be used in crosses, to prevent the entrance
of foreign pollen. And lastly, the pollen should be applied
to the stigma when that part is in a receptive condition.

Mature potato flowers should be examined so that one
may become familiar with their structure. One should
learn when the anthers are mature and when the stigma
is ready for pollination. Just before the bud unfolds
the flower to be used as a seed parent is opened with a
pair of fine-pointed forceps. All the stamens are care-
fully removed, being careful not to break any or to leave

80 The Potato

parts of them in the flower. This must be done before
the pollen is mature. All near-by flowers should be re-
moved and buds other than those emasculated. As the
flowers invariably fall off when bagged, this precaution
must be omitted. The potato is not frequently cross
pollinated (Salaman) and the danger of contamination
is slight. It is necessary to tag the flowers thus treated
in order to know later on when to pollinate them. The
tag should bear the date of emasculation and other facts
of which the hybridizer wishes to keep a record. A
day or two after emasculation, the pistils of the emascu-
lated flowers should be examined. When the tips have
turned a slightly darker color and look sticky, they are
ready to receive the pollen.

As the pollen is usually borne in small quantities, it
is well to open the anthers with the point of the forceps
and scrape it out on to the thumb nail or on to a watch
crystal. A thin film of pollen on a watch crystal will
pollinate a number of blossoms. It is customary to make
two or three pollinations on the same flower in order to
catch it in a perfectly receptive condition. Once the
ovary starts to swell, there is little likelihood of the
flower falling off. The berry should be picked off when
fairly dry and before it falls off and rolls away. A record
should be kept of the dates of emasculation and polli-
nation, and of the parents concerned in each cross.

Potato seed should be washed free of pulp and care-
fully dried, in the fall. If left in the pod, it is likely to
decay. Each pod normally bears from one to three hun-
dred seeds. The seed should be planted indoors in March
or April. The seedlings are potted up when they need
moving, and set out in the field in June. They should
be planted about two feet apart.

Potato Breeding 81

Shoots are sent down into the ground from the axils
of the first leaves, and it is on these that the tubers are
borne. As a rule, the tubers for the first year vary in size
from that of a marble to that of a hen's egg. In unusual
cases single tubers have been obtained the first year
which weighed over a pound. Wilson ^ reports a total
yield of 6 pounds 3 ounces for a single seedling plant.

It is often necessary to plant the tubers for another
year or two in order to secure plants which will bear a
normal crop of good-sized tubers. The tubers should be
harvested separately for each plant, put in paper bags,
and carefully stored until spring. Usually one is able
to make his final selection the second year, but in some
cases it is necessary to plant the tubers again before he
can be sure that his choice of strains is a wise one. The
tubers should be planted about 40 inches apart the sec-
ond year to allow a careful study of individual plants.

One ought to remember that it is comparatively easy
to produce new varieties of plants, and that the mere
fact that we have secured new sorts does not mean
that they are worthy of culture. Any new variety of
plant should be distinctly superior to others on the mar-
ket in at least one respect. The markets are already
cluttered with mediocre varieties. Set your ideals high and
do not be content with anything which falls short of them.
Also do not waste time trying to select good qualities in
strains where no such possibilities exist. Selection will
not build up characters which are not potentially present.

In spite of the many hindrances to hybridization, some
careful studies have been made on the inheritance of
characters in the potato. We must remember, however,
that in some cases at least, the material studied was not

» Wilson, J. H. High, and Agri. Soc. Scot. Trans. 1907, pp. 74-92.
G

82 The Potato

pure. Perhaps it would be safest to look upon the results
as showing certain tendencies in heredity, rather than as
accurate character analysis. Salaman ^ ^ of England and
East ^ of this country have done most of the mendelian
work on the potato. A resume of their work will be given
in the sections that follow :

Stem color. — Some varieties of potatoes have pure green stems,
while others have traces of purple varying from light purple to al-
most black. The purple seems to be partially dominant over the
green. The pure greens appear to be recessive and to breed true.
Salaman ^ found that the deep purple stem color of the Congo gave a
good mendelian segregation. No ratios were given.

East {loc. cit.) reports the following: One purple-stemmed vari-
ety when selfed gave only purples. Four piu-ple-stemmed varieties
gave both purple and green when selfed. Four green varieties when
selfed gave only green. A pure green X a heterozygous purple gave
6 purples and 7 greens — RR X DR.

Flower color. — Potato flowers may be either white, heliotrope or
shades of purple. The color is usually confined to one or the other of
the surfaces of the flower. In all the domestic varieties studied by
Salaman {loc. cit.) the color was limited to the upper surface. S. tube-
rosum had color only on the lower surface. In S. rcrrucosum the
color appeared to be present on both sides of the flower.

East {loc. cit.) reports one purple which broke up into 14 purples
to 5 whites when selfed. He says that purple is probably dominant
to white.

Color in the tubers. — The skin of the tuber may be either white
(yellow), red or purple. The flesh in like manner may be either
white or colored. Purple-skinned varieties often have white flesh,
and white-skinned sorts may show traces of color when cut open.
Salaman ^ says that these colors are all due to pigments dissolved in
the cell sap.

' Salaman, R. N. The Inheritance of Color and Other Characters in
the Potato. Journ. Gen., Vol. 1, 1910-11.

= Salaman, R. N. A Lecture on the Hereditary Characters of the
Potato. Roy. Soc. Hort. Journ., 38 : 34-39 (1912-13).

3 East, E. M. Inheritance in Potatoes. Amer. Nat., U: 424-430
(1910).

Potato Breeding 83

East found that purples when selfed gave in some cases only
purples; in other cases, purples and whites; and in still others,
purples, reds and whites. Reds when selfed gave either reds alone,
or reds and whites. Whites gave only whites. No mosaics of red
and purple were obtained. The conclusion was that red is epi-
static to white, and purple, to both red and white.

Salaman ^ selfed a red-tiibered plant of the variety Flourball and
got a ratio of 9 reds : 7 whites, suggestive of the action of two pairs
of factors. He believes that chromogen, a color base, is present in
all tubers. In the red tubers he assumed the action of an R factor
for color and a D factor which develops R. The second generation
would then give : —

9 RD — red

3Rd]

3rD [ — white

Ird J

The red-tubered plant which Salaman self-fertilized was assumed
to be of the constitution Rr Dd.

The Congo X Flourball (heterozygous for red) gave in Fi 13
black : 12 red : 4 white.

Salaman holds that a factor for purple — P — is necessary in addi-
tion to the R and D factors to give purple. He has on four different
occasions united strains bearing white-skinned tubers to get colored
types. This may be a case of factor interaction similar to Bateson's
case of complementary colors in the sweet pea.

Solarium etuherosum seems to have an inhibitor to the formation
of purple in the tubers.

Flesh color. — Very little work has been done on this character.
Salaman notes that the color of flesh is inherited independently of
skin color. He says that colored flesh is apparently due to the
action of one pair of factors.

Shape of tuber. — Both East and Salaman found roundness recessive
to other shapes. Round jiotatoes bred true in all cases. Salaman
found that long tubers bred true for long axis, but often varied in
diameter and hence in shape. Many oval-shaped potatoes were
found to be heterozygous and to break up when selfed into round,

' Salaman, R. N. The Inheritance of Color and other Characters in
the Potato. Journ. Gen., Vol. 1, 1910-11.

84 The Potato

oval and elongated. The kidney and cylindrical shaped tubers have
about the same length of axis, but seem to have different factors de-
termining diameter.

Depth of ei/es. — The deep eye is a recessive character and breeds
true. Shallow eyes are dominant over deep eyes, but often not com-
pletely so.

Steriliti/. — Salaman ^ finds that a tendency toward sterility is
dominant over a fertile condition of the pollen. In a cross of Record
(no pollen) X Flourball (abundant pollen), the Fi generation gave
12 pollen-bearing plants and 20 wnth no pollen. One of the sterile
(for pollen) Fi plants crossed with the male parent used above gave
19 pollen bearing to 20 non-pollen bearing. This is practically the
1 : 1 ratio which we should expect to get from a cross between a
heterozygous and a pure recessive.

Stolon length. — The stolons on which the tubers are borne are un-
usually long in the species, S. Commcrsonii and S. verrucosum, often
reaching 6 feet or more. In the domestic varieties the stolons
average 9-12 inches. Very long and very short stolons breed true.
Intermediate stolons break up into various lengths, suggesting the
action of multiple factors. Salaman ^ thinks there may be two or
perhaps three pairs of factors involved.

Plant habit. — Salaman ^ states that upright and prone habit of
plant are due to the action of one pair of factors. A duplex condi-
tion of the factor for uprightness gives a perfectly upright plant.
Heterozygotes, Aa, are upright at first, but droop toward the close
of the season. Prone plants have the constitution aa. Both prone
and upright plants bred true to type. Intermediates gave a ratio
of 1 upright : 2 intermediates : 1 prone, when selfed.

Shape of berry. — The seed berries of domestic varieties of pota-
toes are round. Those of the wild species tend to be long. Salaman
concludes that one pair of factors is involved. He believes the long
berries to be due to a du])lex dose of a factor for length. When the
length factor is simplex, a heart-shaped berry results. The double
recessive factor gives round berries which breed true to shape.

' Salaman, R. N. A Lecture on the Hereditary Characters of the
Potato. Roy. Soc. Hort. Journ., 38 : 34-39 (1912-13).

Potato Breeding 85

REFERENCES

East, E. M. A Study of the Factors Influencing the Improvement

of the Potato. III. Bui. 127, 1908.
East, E. M. Inheritance in Potatoes. Amer. Nat., '44-' 1910, pp.

424-430.
Fraser, S. The Potato. N. Y. (Orange Judd Co.), 1-185, 1901.

Breeding and Selection, pp. 171-177.
Fruwirth, C. Die Ziiclitung der landwirtschaftlichen Kultur-

pflanzen. Vol. 3, Berlin, 1905.
New^ian, L. Plant Breeding in Scandinavia. Ottawa (Can. Seed

Growers Association), 1912, pp. 193. (Potatoes, 168-182.)
Salaman, R. N. The Inheritance of Color and Other Characters in

the Potato. Journ. Gen., Vol. 1, 1910-11, 7-46, pis. I-

XXIX.
Stuart, Wm. Potato Breeding and Selection. U. S. D. A. Bui. 195

(professional paper), 1915, pp. 35, pis. XVI, figs.
Waid, C. W. Results of Hill Selection of Potatoes. Amer. Breeders

Association, Ann. Rept., Vol. 3, 1907, pp. 191-199.
Webber, H. J. Methods of Breeding and Improvement of the

Potato Crop. Cornell Farmers' Reading Course Bui. 43,

1909, pp. 753-768.

CHAPTER V

CLIMATE, SOILS AND ROTATION

By Daniel Dean

The climate of most parts of the United States is not
well suited to the production of the potato. The heat of
summer is too great and the water supply in the soil and
in rainfall during the growing season is too small. It is
not known what are the possibilities of the potato in the
mountain regions of South America from which it was
brought by white men in the sixteenth century, but it is
certain that up to the present time growers of north-
western Europe have often secured higher yields to the
acre than those of the United States. One great reason
for this fact is the difference in climate. The most famous
potato-growing regions of Europe are several degrees
north of any part of the United States, except Alaska.
The average summer heat of northern Germany is esti-
mated by the United States Department of Agriculture at
nearly ten degrees Fahrenheit lower than that of most of
the potato-growing sections of the United States. The
climate of the principal potato-growing regions of Europe
is so cool that Indian corn is not grown in them, while
there is heat enough for corn in most of the northern
United States and even for cotton in the South. Most
of northwestern Europe has very heavy rainfall because
of the Gulf Stream. The potato is grown in the United
86

Climate, Soils and Rotation 87

States because of its high value for human food, not be-
cause of favorable conditions. These facts are emphasized
because knowledge of the nature of the potato plant helps
the grower to adapt his methods to his local conditions
to secure the best results. Except in northern Maine
and the adjoining provinces of Canada, there are few
parts of America w^ here summer heat and moisture do not
limit the yield of the potato to a figure below the best
possibilities of the plant. Methods which prevent the
effects of these two factors result in largely increased
yields. In occasional seasons, as in parts of New York
in 1909 and 1914, the climate is favorable and large yields
are grown. It might be possible in such years to get
yields equal to those of northwestern Europe, but it
would be necessary to equal their large expenses for addi-
tional labor, seed and fertilization and this w'ould result
in heavy loss in the other years when climate limited the
yield. Hot and dry years are known in Europe, but are
the exception instead of being the rule as in most of the
United States.

The United States Department of Agriculture Year-
book for 1914 gives the average yield of potatoes to the
acre for the whole United States for ten years as being
96 bushels, while that of the state of Maine, with cool and
damp climate, for the same period, was 206 bushels.
The figures for the countries of northwestern Europe are
311 for the Netherlands, 388 for Belgium, 210 for Great
Britain and Ireland and 200 for Germany. Yields are
lower in the warmer or drier countries of Europe, being
130 in France, 115 in Hungary and 106 in Russia. A
similar contrast is marked between hot Australia with an
average of 101 bushels and cool New Zealand with 216,
though both are settled by the same race of people.

88 The Potato

The warmest province of Canada, Ontario, averages 121
against 207 for the cool and moist maritime provinces
and 229 for British Columbia.

Land is much higher in price in the potato-growing
regions of Europe than in America. An extreme case is
on the Island of Jersey, where land is worth $1000 to
S2500 an acre. The annual rental under the tenant sys-
tem common in Europe is often higher than the sale
value of an acre in sections of the United States which
raise millions of bushels each year. Labor is much
cheaper in Europe than in America, allowing the use of
very intensive hand culture at low cost. If European
growers are to secure a living profit above their high
rentals, they must farm this high-priced land very inten-
sively with large expenditure of cheap labor, seed at
the rate of an average of over 37 bushels to the acre and
heavy fertilization.

American agriculture has been developed in the direc-
tion of heavy production to each worker engaged rather
than in that of large yield to the acre. The high-priced
day's work is the unit, not the high-priced acre of land.
From the time when the Massachusetts Bay colonists
"went west" to the Connecticut Valley in 1635, it was
necessary to go westward, even to northwestern Canada,
for there has been a new region of cheap land awaiting
settlement. Almost until the present time, the competi-
tion of new soil of virgin fertility has kept down the price
of farm produce and of land in the older settled communi-
ties to figures far below those of Europe. An even worse
effect of this competition has been that little attempt has
been made to keep up soil fertility. Methods of farming
suited to frontier conditions of low prices and highly
fertile soil have continued in use too long. Land is now

Climate, Soils and Rotation 89

rapidly rising in price, and methods of increasing the yield
of crops will become more important than before.

The high cost of labor in the United States compared
with that of land has resulted in the invention and use
of labor-saving machinery for nearly every process of
farming by which the power of horses or of engines has
displaced that of human muscle. Machinery cannot so
much increase the production to an acre as the production
to each worker engaged in farming by increasing the num-
ber of acres farmed by each. For example, the use of
horse-drawn tools compels a wider spacing of potato
rows than where most of the work is by hand labor.
This reduces the yield to the acre by reducing the num-
ber of plants. On the island of Jersey, rows of potatoes
are spaced 16 inches apart and 24 to 27 in other parts of
Europe, compared with 33 to 42 in America.

FACTORS INFLUENCING POTATO CULTURE

Study of the factors governing the choice of methods
for the culture of the potato shows that eight are of prin-
cipal importance: (1) heat in air and soil; (2) water;
(3) soil texture ; (4) available plant-food ; (5) drain-
age and soil air; (6) the "critical period" in the life of
the plant ; (7) type, variety and strain of the seed ;
(8) diseases.

The term "limiting factor" is frequently used in other
connections and is peculiarly appropriate in potato-
growing. Any one of the above factors may be inhibiting
in some conditions and may be able to place a limit on
the size of the crop which cannot be removed by the
others being favorable. For example, all farmers are
familiar with the loss of yield caused by drouth, although

90 The Potato

not all know that the direct effect of great heat is per-
haps even more harmful than the lack of water. The
results of unchecked attacks of insects like the Colorado
potato-beetle or of the late blight and rot, are other
familiar examples. The potato-grower who would raise
good yields every year through a series of years must
study very carefully every factor which enters into the
growing of potatoes under his particular conditions,
with the idea of making sure that no one condition
will limit the results of his labor in other directions.
Such care counts heavily in increasing the income of the
farm, because seasons in which a crop is generally poor
from any cause are the ones in which prices are high.

Heat

Numerous experiments have shown that temperatures
in the soil above certain limits injure the vitality of the
potato plant. The extent of the injury depends on the
degree of heat and on other injurious factors, as drouth
and insQct injury. The effect varies from reduction in
yield to practical failure with tubers ruined for use as
seed. Potatoes are not grown in the South in midsum-
mer. When grown in the months of late winter and spring,
the vitality of the tubers for use as seed is ruined by the
heat at the time the tubers mature. The "second-crop"
for seed in the South is planted in July or August and
forms its tubers in the cool weather of late fall. At this
time seed of good vitality is obtained. Near the Canadian
line and in the Rocky Mountain region there is little more
time in the whole growing season than is needed by the
late main-crop varieties. When hot seasons occur there,
as at Ottawa, Canada, in 190G-7-8, and at Greeley, Colo-

Climate, Soils and Rotation 91

rado, in 1911, there is no way of avoiding the heat by
early or late planting. In intermediate sections like those
from Long Island through to Iowa, growers avoid the
effects of summer heat to some extent by planting
either very early or very late.

Another method used more or less unconsciously by
growers to prevent the effects of summer, is the use of
heat-resistant varieties. The INIcCormick or Late Hoosier
is used in Virginia and INIaryland in summer because of
its peculiar ability to produce crops in weather too hot
for any other variety. The Rural or Blue-Sprout type
is the one which is grown more than any other in the
LTnited States. It owes much of its popularity to the
fact that it will yield well in hot and dry seasons. The
use of the Green INIountain or White-Sprout type is
mainly confined to the cooler sections, like INIaine, because
of its inability to stand heat as well as the Rural type.
The Triumph, Cobbler and Early Ohio types are used to
avoid extreme heat by growth in early spring rather than
by heat resistance.

Heat is such a decisive factor in the growth of potatoes
in most of the United States that growers must ever keep
its effects in mind if they are to succeed with the crop.
Many of these methods of culture now used have been
forced on growers unconsciously by the influence of heat
on the plant. ]\Iuch is to be expected in the future from
further investigations. Straw mulches have been found
very beneficial in the hot regions of the western plains to
insure coolness in the soil. It has been proved that
thorough spraying with bordeaux mixture greatly reduces
the injury from heat. This is shown by some of the
gain from spraying in hot seasons when blight and insect
injury are absent. A possibility is in the use of over-

92 The Potato

head irrigation in humid sections. One of the greatest
needs of potato-growers everywhere is a new variety
possessing the table quahty, yield and appearance of
those now in use together with the heat-resistance of the
McCormick.

Water requirements

Lack of sufficient water is often a Hmiting factor on
the yield of potatoes. Many experiments indicate that
about 400 tons of water are used by the potato plant for
each ton of dry matter produced, or over three tons for
each bushel. This equals 3 inches of rainfall for each
100 bushels to the acre. Study of Weather Bureau
records of rainfall shows that the average amount in the
entire growing seasons in most potato-growing sections
is only 10 to 18 inches. The losses from run-off and
from evaporation are so heavy that this factor must
be provided for if exceptional yields are to be raised.
Methods of conserving the soil water left by winter rains,
for the use of the crop, are of great value. The use
of ordinary surface irrigation in the West and of over-
head irrigation in the East produces much heavier yields
than when rainfall is the whole dependence. With these
methods, yields of over 500 bushels to the acre are common.

Surface tillage to prevent evaporation and the incor-
poration of organic matter with the soil are the principal
means of conserving moisture. Plants on rich soil or
when manures or fertilizers are used, are able to secure
their plant-food from the soil by the use of less water
than when grown on poor soil. Any means of extend-
ing the growth of roots makes more water available.
The great need of water for the potato crop comes at the
time when the tubers are forming. It is a matter of

Climate, Soils and Rotation 93

common observation that a small amount of rainfall at
this time may be worth much more than larger amounts
at other times. As this comes immediately after the
critical period in the life of the potato, it will be seen that
every effort should be made to keep the plant well sup-
plied with water by tillage, organic matter, and the like.

Soil texture

The root system of the potato is weak and small com-
pared with that of other standard farm crops, such as
corn. It is especially weak in penetrating heavy soils.
In any soil, loose texture greatly favors the potato by allow-
ing wider and deeper distribution of the roots. The de-
velopment of the tubers is checked and rendered irregular
unless the soil is loose and open in texture. Most of the
early crop for sale in summer is grown on sandy soils.
On account of their advantages in structure, potatoes would
be raised only on sandy soils did they not have other dis-
advantages which offset the value of good structure and
earliness. Too great soil heat and lack of moisture often
limit the yield of potatoes grown on sandy soils as a late
main crop in summer. Much of the w^ork of the potato-
grower must be directed to give heavier soil types a struc-
ture more loose and open. Increasing the proportion of
organic matter loosens up the structure of soils. Some of
the greatest potato-growing soils naturally possess plenty
of organic matter, as the Aroostook soils and the tule
lands of California. The increased value of irrigated
soils for the potato-growing where organic matter is sup-
plied by rotation with alfalfa, or the use of humus-produc-
ing cover crops in the South, shows the importance of or-
ganic matter. There are few American soils which are not

94 The Potato

improved for the potato by increasing their organic matter
content. Under most American methods of cultivation
the proportion is reduced ; consequently yields are grad-
ually' reduced, and in the case of some varieties, like the
Burbank, even the shape of the tubers may be injured
by development in the less mellow soil. Cheap and easy
methods for the increase of the supply of organic matter
are among the greatest needs of potato-growers.

Available plant-food

For several reasons the potato is less able to secure its
plant-food from the soil as well as many other plants un-
less it is in readily available condition. For example, the
use of insoluble phosphoric acid in the form of raw rock
phosphate often gives good results on other crops but
seldom on the potato. A large supply of organic matter
in the soil, good drainage and a slightly alkaline condition
are essential to the liberation of the stores of plant-food
in the soil for the use of plants. Fertilizers do not pro-
duce their full effect on potatoes unless these conditions
are present. If the latter are favorable, fertilizers seldom
fail to increase the yield. The use of fertilizers on potatoes
is increasing very rapidly. In Maine, Long Island, New
Jersey and through the coast-trucking section from Nor-
folk to Florida, over a ton to the acre is often used. The
value of potatoes for human food is so high that the price
received for the crop makes such use profitable. There is
also a residual effect of the fertilizer on the succeeding
crops of a rotation, to be considered. Part of this effect
may be due to a favorable effect of fertilizers on the soil
bacteria.^

1 U. S. D. A. Off. of Exp. Sta. Bui. 194.

Climate, Soils and Rotation 95

Drainage and soil air

All crops require more or less air in the soil for health
and growth. The need of air in the soil is one reason
why potatoes do poorly on too heavy clay soils. One
reason for the ridge culture so much used on wet or heavy
soils like those of the Aroostook region and the volusia
soils region is the need of drainage and soil air. Air is
necessary to the work of bacteria in the soil and to the
chemical changes which make plant-food available in
it. Water is necessary to plant growth, but too much
in the soil is injurious. Tile-drainage removes the sur-
plus of water quickly after rains and so extends down-
ward the area in which roots can live. Western potato-
growers who irrigate have learned to apply the water in
furrows between the rows. The rows are ridged high
enough to allow the forming tubers and a large part of
the root system to remain above the level of the water in
the furrows. The potato is very sensitive to the presence
of too much water in the soil. This is shown by the
quickness with which potatoes die after being covered
by floods or by standing water after rains. The immer-
sion of the tops for a few days or even hours is fatal.
Too much water in the soil will kill part of the roots, and
greatly reduces the vitality of the plants.

Critical period

The potato is now very different from the wild plant
before its domestication. Then it produced few tubers,
and these were very small. The present varieties have
been produced from the original wild stock by hun-
dreds of years of breeding and selection to meet the de-

96 The Potato

mands now made upon the plant. The yield of tubers
has been enormously increased above that of the wild
plant. Many shapes and colors have been discarded to
keep the few which suit the eyes of civilized men. The
length of the life of the potato plant has been shortened
from nine months or more in the wild state to only three
or four months. Vast numbers of seedling varieties
which may have possessed greater natural vigor have
been discarded to keep those which possess these quali-
ties. It is not surprising therefore that the potato plant
is not a strong one. One period in its life is especiall}^
precarious. The cultivated plant now produces much
less seed than the wild plant, some kinds seldom or never
blossoming; but blossoming is still a demand upon the
strength of the potato. In the wild state the tubers were
set after the seed formation. Under domestication the
life of the plant has been shortened and the two processes
overlap. When this time comes in hot weather, as with
the late main crop of the northern states, the heat and
drought which occur so often make the poorest possible
conditions for the potato. Insects, diseases and careless
methods of cultivation often further reduce the vitality
of the crop. This has been called the "critical period"
of the life of the potato. If it is passed in high \-ig<)r, the
potato has later a more or less indeterminate growth.
That is, there is no clearly defined time for its maturity,
as with grain crops, but instead it gradually weakens, all
the time increasing the yield of tubers. This condition
occurs but seldom in the United States on account of the
heat of summer, but it is an ideal towards which potato
growers should strive. Production of a high degree of
vitality in the growing plant in its early life and good
soil conditions and care during the hot weather, will carry

Climate, Soils and Rotation 97

the crop safely through heat and drought which would
not only badly reduce the yield but also spoil the crop
for use as seed. Practically the whole yield is produced
after this time.

Type, variety and strain

In this chapter, reference to the seed used is made to
show that the variation between different types, varieties
and strains allows the grower considerable latitude in
adjusting the potato crop to different conditions. The
use of quickly maturing types in the South and of heat-
resistant types in all but the most northern sections are
examples of these adaptations. Much effort has been
expended in the effort to find new varieties possessing the
quality of resistance to some of the more serious potato
diseases, but with little success as yet.

Diseases

Several of the most important potato diseases affect
cultural methods. Examples of such are the use of long
rotation to eliminate common scab, rhizoctoniose, the
nematode eel worm and the fusarium wilt, from affected
soils. Early spring planting to insure maturity before pos-
sible attacks of late-blight is employed in some sections.

GENERAL TYPES OF POTATO-GROWING IN THE UNITED
STATES

Conditions of climate, soil, seed and markets vary so
much that every grower has his problem to select the
methods which will give him the most profitable results.
The climate is something the grower cannot change.

98 The Potato

The markets have demands which the individual can do
little to change. But in the selection of methods he has
wide range of choice. The great variation in the climates
and soils of as large a country as the United States makes
for a wide range in culture methods. Broadly speakmg,
most of the potato-growing of the United States may be
divided into five general types :

(1) The early truck crop of the southern states, extend-
ing to about the latitude of Washington. This belt is
characterized by extreme summer heat which prevents
growth in summer, excepting that of the heat-resistant
McCormick variety. The crop is grown in the cool
months of winter and spring for shipment to city markets
because too perishable to store in the hot summer. Most
of the seed is imported from the north or grown in the
cool fall months as a "second crop." Commercial fer-
tilizers are heavily used in this belt. The summer heat
does not permit growth of most of the perennial hay crops
used in other sections. Annuals are mainly used for hay
and for the cover-crops that are often raised to prevent
erosion and loss of plant-food in winter. Owing to the
higher prices for extreme earliness, only short-season early
maturing varieties are used and these are usually dug
immature. Less machinery is used than in other sections.

(2) The northern belt of the principal potato-producing
states. This extends from Maine to North Dakota and
down to the latitude of New York City. This belt sup-
plies the cities and southern states during the fall and
winter and competes with the southern truck crop from
April to July. The climate here is cool enough for the
potato to maintain its vitality in most seasons, if given
good care. Early varieties are now grown but little
except for shipment South as seed stock. The use of fer-

Climate, Soils and Rotation 99

tilizers is steadily increasing, being very heavy in the
East from Maine to New York, Spraying with bordeaux
mixture for the late blight and rot is prevalent in the East.
Digging comes so near to freezing weather that the gnan
crops grown in rotation with potatoes are those sown in
spring. Oats are used mostly with spring wheat in the
Red River section. Oats and peas and barley are grown
to less extent.

(3) An intermediate belt between these two from
Nebraska to New Jersey and Long Island. Potatoes
from this belt come on city markets in summer and early
fall, part being stored for winter shipment. Summer heat
is not so dangerous as in the South, but there is usually
an effort to avoid its effects to some degree either by
planting early enough to get the crop nearly mature
before midsummer or else late enough to have much of
the growth come in the cool fall months. The effect of
summer heat on seed vitality is often severe, but a large
share of the seed is grown locally. The use of imported
seed from the North is increasing, particularly in the
regions of more intensive culture, such as Long Island.
Winter wheat and rye often follow the potato in rotation
in this belt.

(4) The irrigated sections of the West, destined to
great extension in the future. The problems of the
potato-grower in other sections are here largely replaced
by those peculiar to the growth of the crop under irriga-
tion. New systems of culture have been worked out to
meet the new conditions. Control of moisture has en-
abled some of the heaviest yields ever grown in the
United States. Owing to the natural high fertility of
arid soils, fertilizers are unknown. Nitrogen and organic
matter are secured by rotation with alfalfa.

100 The Potato

(5) Potato-growing by the so-called dry-farming methods,
and local conditions such as the delta section of California,
are as yet less important types.

SOILS

The choice of the soil on which to grow the potato is
peculiarly difficult because of the fact that those which
best meet the needs of the plant in one respect may be
unfitted for it in others. Sandy soils permit free develop-
ment of the root system, are well drained and are capable
of early tillage in spring. Although usually poor soils
unless fertilizer is applied, the growth of the crop is rapid ;
and for these reasons most of the early truck crop of the
South is grown on sandy soils, as earliness secures the
highest prices. The great problem of potato-growing on
sandy soils is that of sufficient water supply at the time
the tubers are forming. This tendency to drought and
heat injury of the crop has operated to lessen the use of
sandy soils in the northern states for the late main crop
In favor of soils cooler and more retentive of moisture.
A large proportion of organic matter is of great value to
sandy soils in increasing available fertility and the ability
to hold moisture. The organic matter in sandy soils is
easily exhausted by tillage, and constant effort is needed
to keep it up to a high standard.

The larger part of the potato crop of the United States
is grown on soils ranging in texture from sandy or gravelly
loam to clay loam. Such soils are capable of holding
enough moisture to supply the growing plant continu-
ously, are cooler than the sands, and are usually of fair
fertility if not too deficient in organic matter. While the
extension of the roots and the formation of the tubers

HH^'"^

L^

E

^^

i

^^^^1

Plate VIII.

Seed potatoes. Top, different ways of cutting.
torn, good and bad types for seed.

Bot-

Climate, Soils and Rotation 101

are not as easy as in sandy soils, these types are not heavy
enough to prevent success with the potato. Clay soils
are too hard and heavy for the potato. Too much water
at times and poor ventilation often affect the health of
potatoes on clays. Careful tillage, tile drainage and the
incorporation of organic matter lighten clay soils until
they will produce good crops of potatoes in most years.
Except in special cases, as near-by markets, it usually
pays better to grow potatoes on lighter soils and use the
clay soils for crops more adapted to them, as grass.
Muck soils, as the tule lands of California, often produce
large yields of potatoes. The quality is likely to be poor.

The importance of organic matter in the soil is seldom
fully appreciated by American farmers. Most American
soils outside of the arid regions contained more organic
matter when first brought under cultivation than now.
The gradual depreciation from year to year is not noticed
until heavy loss in fertility has occurred. Another cause
which has contributed to the depreciation of American
soils is the low price of farm produce. The Department
of Agriculture estimates the cash labor income of Ameri-
can farmers to average about $320 a year besides the
items secured from the farm as house-rent, garden, and
the like. Too often this condition leads to robbery of
the farmer's capital, the soil. The settlement of the last
free land has led to a rise of the prices of farm products,
which now makes it profitable to replace and increase the
lost organic matter and lime fertility of older soils.

Organic matter has great power to absorb water and
hold it for the use of plants. The potato is very sus-
ceptible to injury from lack of water, making this property
of organic matter of great value. The physical nature of
any soil is greatly changed by organic matter. Heavy

102 The Potato

soils are lightened, often to a degree which insures
success instead of failure with the potato. Sandy soils
are improved by their particles being bound together.
The presence of abundant organic matter makes the soil
more healthy as a home for plants and for the beneficial
soil bacteria. Both need water and air. The plant-food
in the organic matter is in condition to feed the crop as
fast as it decays and breaks down. Indirectly the decay
helps to dissolve the mineral plant-food in the soil.

Many kinds of bacteria and other microscopic forms of
plant life are found in the soil. Their action and value
are seldom understood by farmers. Too often the word
"bacteria" conveys only the idea of disease, or at most
that of the particular bacteria associated with legumes
to take nitrogen from the air. These latter form but a
fraction of the microscopic life of the soil, part of which
is beneficial and part detrimental. Organic matter in
and on the surface of soils is the food of many kinds of
bacteria, and is broken down by them to forms which
plants can assimilate. The nitrogen of organic matter
is changed first to ammonia and then to the soluble
nitrate form. Other bacteria like the azotobacter group
take nitrogen directly from the air without being asso-
ciated with any particular plants. The solution of
mineral plant-foods is helped by some kinds of bacteria.
The statement is generally true that the fertility of a soil
varies according to the number of bacteria present. The
number of the beneficial forms is increased by attention
to maintaining the best conditions for their growth, as a
large supply of organic matter for their food, an alkaline
soil, sufficient water but not too much, and sufficient
soil air.

Organic matter in the soil is of so great importance to

Climate, Soils and Rotation 103

the potato crop that methods for maintaining its supply
need careful study. In the natural wild state the soils
of humid regions receive constant additions of organic
matter from the death of plants and the leaves of trees.
The richness of newly cleared forest land and of the west-
ern prairies when first broken are examples familiar to all.
Under cultivation most crops annually produce more
organic matter than do wild plants, but in most cases only
a fraction is returned to the soil. Part is shipped away
from the farm for the use of man or of animals, part is
destroyed by the animals fed on the farm in the process of
digestion and part is lost in handling the manure. Opera-
tions of tillage and exposure of bare soils to the air rapidly
use up organic matter. A few American soils are being
handled in waj's which increase their organic matter, but
most of them probably are not.

The principal method of maintaining soil organic
matter is that of crop residues. All crops leave part
of their organic matter in the soil after being harvested,
the proportion varying greatly. When potato tops are
burned to prevent disease, very little organic matter is
left in the soil from the roots. Other plants have more
extensive root systems and also leave other residues in
the form of stubble. A larger proportion is left when
only the grain or seed of crops is removed and all stalks
or straw is left on the land. Feeding off crops in the
field, as in "hogging down" corn, leaves all the organic
matter except that destroyed in the process of digestion.
In practice, hay crops leave more residues than others
like grain and potatoes. It is unfortunate that so little
attention has been paid to hay crops in the United States
compared with that given to the inter-tilled crops and
to the grains. Tillage, manure, fertilizer and care are

104 The Potato

too much concentrated on the other crops of a rotation
and the hay is left to grow as best it can. The handling
of meadows and pastures is far better understood in
Europe than in America, some being hundreds of years
old. The use of better seed mixtures, of better methods
of seeding, of better adaptation of the different hay crops
to soils and of better fertilization will not only add directly
to the yield and value of hay crops, but will increase
greatly the yields of the other crops of any rotation by
increasing soil fertility.

The statement is often made that when farm crops are
fed to animals, the entire crop is returned to the soil in
the manure. This is nearly true in regard to the mineral
elements when the manure is well cared for. But the
organic matter is very largely lost in the process of diges-
tion. Over sixty per cent of that of hay and straw is
used in this way, somewhat less in the case of grain feeds.
In addition there is the loss in the handling of the manure.
While the remainder is in more quickly available condi-
tion than in straw or in stubble, the question of whether
to harvest the crop to feed or to return directly to the
land will depend on the profit expected from feeding, the
need of the soil for organic matter, the cost of labor and
the effect which either practice will have on carrying out
the rotation in use. The millions of people in cities must
be fed. The organic matter and mineral plant-food in
the produce shipped is lost to the farm, but other means
can be found of replacing both. The price of farm prod-
uce within easy shipping distance of cities is often greater
than its value as feed for animals on the farm. Under
these conditions it pays to sell crops and keep up soil
fertility by fertilizers, catch-crops, and by attention to
increasing crop residues left in the soil. ' Prices for farm

Climate, Soils and Rotation 105

produce are now high enough so that this can be done.
The great danger which the history of American farming
has shown is that the temptation to sell off cash crops
too closely is so great that attention to maintaining fer-
tility is put off too long. Animal husbandry has the
advantage in practice that the return of the manure to the
soil is a necessary part of farm work and soil robbery is
less likely to result.

The third way to return organic matter to the soil is
to return the entire product of any crop. Any crop may
be used for this purpose, although, in practice, those used
are usually of low cash value. Great need of soil organic
matter and increase in yield incident to such a valuable
cash crop as the potato may make it advisable to plow
under crops like clover which would be inadvisable in
other crop rotations of less value. The term "green-
manure" refers to crops plowed under before maturity.
The term "catch-crop" refers to one grown between
crops raised for sale or feed or for other uses. The term
"cover-crop" is usually restricted to those grown to
occupy the soil during the winter. In addition to supply-
ing organic matter, any of these may cover and protect
the soil and so prevent losses by erosion and leaching.
A crop plowed under while still green and immature, and
which contains such a large proportion of water that it
decays quickly, may give only a small net gain over the
cost of seed and planting and the amount of organic
matter destroyed by tillage. Green-manures must be
used with caution wherever their use is likely to reduce
the soil moisture for the following crop. Rye plowed
under in spring is often injurious in this way. The
amount of water needed for large crops of potatoes is so
great that earlj- spring plowing or surface tillage is usually

106 The Potato

advisable to save as much moisture as possible for the
potatoes. Another danger from the use of any form of
organic matter plowed under shortly before planting is
that movement of the soil water may be hindered and
the plants injured for lack of it. So much of the money
value of grain crops is in the seed that it usually pays to
harvest the crop, sell or feed the grain and return the
stalks or straw only to the soil. Many experiments have
shown that the amount of organic matter in any crop
increases most rapidly in the latter part of its life ; so
that in the straw of a grain crop there is likely to be found
more than that in the wliole crop if plowed under a few
weeks before maturity. The value of the grain is several
times the cost of harvesting and threshing. The use of
the hay crops seeded with the small grains to plow under
gives larger net returns of organic matter to the soil,
because, unlike rye, buckwheat, or soy beans, there is no
destruction of organic matter by tillage in planting.

The need of winter cover-crops for soils is least where
the ground is constantly frozen or covered by snow
throughout the winter. Mild and open winters, as in
the South, make it desirable to have the soil covered by
plants which will prevent erosion and save plant-food
which would otherwise leach away. Unless left to grow
too long in spring, there is little danger in humid sections
of loss of enough water to injure later money-crops like
potatoes.

The choice of catch-, cover- and green-manure-crops
for any particular rotation, soil and climate depends on
many factors which differ from those governing the choice
of the money-crops of the rotation only because cover-
crops seldom have a cash value. Those crops of any
rotation which have the greatest value, as is generally the

Climate, Soils and Rotation 107

case with potatoes, naturally govern the choice of others
to a great extent. The degree of its adaptability to soil
and climate, ability to fit into rotation with other crops,
money value, net increase or decrease in soil fertility, and
cost of growing are all to be considered.

ROTATION

It is seldom desirable to grow the potato continuously
on the same soil. The reasons for the rotation of the
potato with other crops are : (1) Plant diseases often
rapidly become worse when crops are grown continuously.
This has often been the case with the potato. Modern
scientific methods of care of seed, selection, disinfection,
spraying and other details of culture somewhat reduce
this danger. (2) In the business management of the
farm, rotation reduces the danger of excessive losses in
seasons of low prices or of poor yields, and arranges the
work of the farm through the season to better advantage.
(3) Weeds are easier controlled under a system of rota-
tion. Those which flourish under the conditions of
growth of one crop may be easily kept down under an-
other. The high value of the potato crop pays for
thorough tillage and care which cleans the soil of weeds
for the rest of the rotation. (4) Insect pests are kept
down easier under rotation. (5) The high cash value of
potatoes justifies considerable sums of money spent on
fertilizers and enables more of the time of the rotation
to be used in producing organic matter to be returned
later to the soil. The thorough culture, late digging and
winter exposure of soil after potatoes in the northern
states rapidly uses up the soil organic matter. The
cheapest and easiest way of replacement is by rotation

108 The Potato

with grass, clover and other hay crops which have a money
vakie as food for animals, and also leave large amounts
of organic matter in the soil from their roots and stubble,
as well as that in the manure from the hay fed. Legumes
are able to draw part of their nitrogen from the air to
increase the soil supply. Some nitrogen is also obtained
from the air in other ways, as by the non-symbiotic
bacteria. This is shown by the great fertility of the wild
prairie soils which have had few leguminous plants.
(G) Different plants draw on the plant-food in the soil
in varying proportions. Consequently a rotation of crops
enables each to secure its plant-food easier than it would
if grown continuously. (7) Though the potato sends its
roots deeper than some crops, there are others, like clover
and alfalfa, which root much deeper. These bring up
fertility from the subsoil, and the roots of potatoes follow-
ing are able to grow lower, even in hard clay soils. ^ (8) It
is believed that plants throw off in the soil in their growth
toxic substances which by accumulation become injurious
to succeeding crops of the same plant but not to others.
(9) The physical condition of the soil for succeeding crops
is improved by the thorough culture given the potato.
Instances of this are the use of wheat following potatoes
without plowing in fall, and oats without plowing in
spring.

The net return of the rotation as a whole must be the
deciding factor in the choice of crops. The potato gives
such large cash returns to the acre and responds so well
to the use of fertilizers that it is usually the most important
crop of the rotation in which it is grown. Wherever this
is true, the choice of the other crops to go with it is largely
governed by their effect on the soil for the production of

1 Colo. Bui. 216.

Climate, Soils and Rotation. 109

the potato. In the northeastern states the most common
rotation is one of a tilled crop like potatoes or corn the
first year, a small grain crop usually oats or wheat the
second year, in which grass seeds are sown. In regions
of the most intensive culture, this hay crop is cut only
one year and in that case it is clover. In others the mix-
ture is clover and timothy with occasionally redtop, which
is cut several years. Further South, where grasses do
not grow well, it is necessary to use annual hay crops like
crimson clover or cowpeas. In the North grass seeds
are seldom sown alone. The practice of summer tillage
before sowing alfalfa has been found so valuable that it is
coming into use for the sowing of the grasses as well,
particularly on weedy soils, or on those on which it is
difficult to get seeds sown with grain to catch.

The relative profit to be expected from the growth of
potatoes, grain and hay determines the number of years
which each will use in a given rotation for any locality.
In New England hay and potatoes are both relatively
more valuable than grain, and each may occupy the soil
for two years out of a five-year rotation. In New York
and Pennsylvania the hay may be cut for several years.
Going South, hay is grown less and less until in the truck-
ing section potatoes are rotated mainly with other truck
crops as spinach and cabbage. In the middle West the
higher cost of transportation of potatoes and hay com-
pared with grain causes the latter to be grown several
years in a rotation, as is often the case in the Red River
section.

Hay plants

Alfalfa is the best crop to rotate with potatoes where
it can be grown with profit, as in the Rocky Mountain

110 The Potato

region. It is a perennial, is deep-rooted, produces several
cuttings to distribute labor and risk of bad weather
through a longer period, yields heavily, is of high value
for either feed or sale, gets part of its nitrogen from the
air and part of its mineral food from the deep subsoil,
and leaves the soil in excellent condition to grow potatoes.
Its use is gradually extending in the eastern half of the
United States as the methods necessary for its growth
become better understood. It may never attain to the
commanding position here which it holds in the agricul-
ture of the western half of the country, but it is certain
to become more generally grown than now. An objec-
tion to the use of alfalfa in a potato rotation in the East
is that the heavy liming generally necessary induces scab
on the potatoes.

The hay crops usually grown in rotation with potatoes
in the northern states are the clovers, timothy and red-
top. Except for growing only one season, red clover has
most of the good qualities of alfalfa. The growth of
either is a sign of land in good condition. Both require
considerable lime in the soil, though clover needs less
than alfalfa. While the potato will make fair crops on
land that is sour and low in organic matter, it grows
better if the soil is in the well-drained and slightly alkaline
condition in which the beneficial soil bacteria live best.
The second cutting of common red clover is often turned
under in potato rotations on account of benefit to the soil.
Mammoth red clover is a larger and coarser variety of
the red. Alsike clover is lighter in yield than the red, but
is able to grow on many poor, wet or sour soils where red
clover will fail. It should be substituted for the red
wholly or in part wherever there is danger that the red
will fail to grow. Timothy is a hay plant of great value

Climate, Soils and Rotation 111

when handled correctly. It will grow on many soils, fur-
nishes a fairly heavy root system and stubble to keep up
soil organic matter, gives a good yield of hay which is
easily cured and finds ready sale at good prices for horse
feeding. The close sod formed by timothy prevents
erosion and helps to keep weeds down. The use of lime,
manure and fertilizers on timothy greatly increases the
yield and keeps it longer at a high production. A very
common fault in the handling of timothy is to let it stand
so long that many plants die out and when the remainder
are turned under there is but little organic matter to
supply succeeding crops. It should be plowed while
there is yet material to enrich the soil. Redtop is a hay
plant seldom appreciated outside of New England. A
prejudice against redtop in mixture in market hay re-
duces the price on account of a common practice of letting
it stand until woody before cutting. Properly handled,
its value for feeding is practically that of timothy. By
the well-known principle that a mixture of grasses yields
better than either alone, redtop increases the yield of
mixtures in which it is included and is particularly valu-
able for humus production on account of its very heavy
sod. It grows in soils too poor, wet or dry for timothy.

The selection of the hay plants to be grown in any rota-
tion with potatoes should be carefully considered with
the idea of building up soil fertility as well as producing
hay for feeding or sale. Alfalfa, red clover, alsike clover,
timothy and redtop require for their growth soils varying
in fertility, drainage and lime content in about the order
named. Potatoes should be rotated with alfalfa where it
succeeds. In all others, and this includes nearly all the
northern and eastern states from the Red River to Maine,
the capacity of the soil determines whether red clover

112 The Potato

should be sown alone, or another mixture. This might
be red and alsike clover, the clovers with timothy or both
timothy and redtop, or perhaps on some of the poorer
volusia soils and others of that low grade of fertility, red
clover is best left out unless limed and only alsike, timothy
and redtop sown.

In southern sections there is difficulty in growing the
northern hay plants mentioned. Reliance must be placed
on annuals for most of the hay and for cover-crops.
Crimson clover, wheat, rye, winter oats, hairy vetch, soy-
beans, cowpeas, peanuts and velvet beans are used in the
southern states for these purposes.

In the West where irrigation is practiced, alfalfa is
used more than any other crop to rotate with potatoes to
supply organic matter. Field peas are also used.

REFERENCES

Agee. Crops and Methods for Soil Improvement.

Brooks. Agriculture, Vol. I, Soils.

Eraser. The Potato.

Grubb and Guh^foAd. The Potato.

Terry. The A. B. C. of Potato Culture.

Bui. 87, Bur. PI. Ind., U. S. Dept. Agr. Authority for " Critical

Period," p. 96.
Bui. 49, Can. Central Exp. Farms, Effect of Heat on Seed Vitality.
Buls. 347, 352, 397 N. Y. (Geneva) Exp. Sta., and Bui. 159, Vt.

Exp. Sta., On Effect of Spraying in Dry Season.

CHAPTER VI

MANURES AND FERTILIZERS

By Daniel Dean

The supply of plant-food elements present in soils will
produce potato crops of varying size according to the
climate, the original natural fertility of the soil-type and
the degree to which it has been reduced or improved in
condition since bringing under cultivation. Manures and
fertilizers are used to add plant-food in forms so easily and
quickly available that the crop wull be able to take up
and use more than it could without them. On account
of its tender nature, compared with other farm crops, the
potato responds well to the use of fertilizers. Manures
and fertilizers are used wherever the increased yield brings
enough in the market returns to meet the additional cost
and leave a profit. For these reasons, the use of fertilizers
is more or less localized in the particular sections where
their use is most profitable. For example, the cool and
moist climate of the Aroostook region of Maine is very fa-
vorable to the production of large yields of potatoes to the
acre. In spite of the great natural fertility of the soils,
these fertilizers are used to the extent of over 1900 pounds
to the acre on the average at a cost of over $30, because
the practice pays. The great trucking region which
supplies city markets from April till autumn and extends
along the Atlantic coast from Florida to Long Island is
nearly all made up of sandy soils of low natural fertility.
I 113

114 The Potato

The comparatively higli prices received for this early crop
makes heavy fertilizing, often over 2000 pounds to the
acre, profitable. By contrast, the irrigated sections of
the Rocky INIountain region often have soils very rich in
the mineral plant-food elements. Though often low in the
supph' of nitrogen, this is obtained by rotating the potato
crop with alfalfa. This would render fertilizers of little
value for these conditions even if the high freight costs
from our present sources of supply did not put fertilizers
out of the question.

Scientists are not fully agreed as to the functions of the
different elements in the soil used by plants. Experiments
have proved that several must be present or plants will
not grow. The common term "plant-food" is applied
from these experiments. Fertilizers have other actions
of value to plants, some well understood, and some which
have only been discovered and are as yet not very well
known. One is their favorable action on the beneficial
bacteria present in the soil.^ Certain fertilizers, by ren-
dering soil conditions more favorable for them, increase
indirectly the fertility of the soil as well as by their direct
action. Our knowledge of these bacteria is limited at
present in some directions, but it is certain that their
importance to agriculture is very great, much greater than
is generally known. One limit to the yield of farm crops
is the amount of water which is available for their use.
This is shown by the great gains from the practice of irri-
gation. Fertilizers practically increase the water supply
by increasing the concentration of the solution of plant-
foods in the soil water and so enable the plants to secure
more from the same amount of water in the soil.-

1 Office of Expt. Sta., Bui. 194.

« U. S. D. A., Bureau of Soils, Bui. 22.

Manures and Fertilizers 115

It is thought that to some extent fertihzers act as disin-
fectants to reduce damage by unfavorable agents in the soil.

FERTILIZER PRACTICES

Elements often present in the soil in too small quantities
for the best growth are nitrogen, phosphorus, potassium
and calcium. Wlien these are added in the form of fer-
tilizers or manure, the yield of most crops is increased.
The extent to which farmers may use fertilizers depends
on the cost of the fertilizer compared with the net value of
the increase in the crop. Another factor which must be
considered is the residual effect of fertilizers on the soil.
In the early days of the use of fertilizers, small applications
were often made without much attempt to maintain the
soil supply of organic matter. When the amount supplied
was sufficient only to give the young plant a better start,
it is probable that the increase in yield removed more of
the plant-food elements than was added in the fertilizers.
Being usually applied to grain or to tilled crops, there
was but little increase in the amount of organic matter
returned to the soil in the plant residues, not enough to
replace that destroyed by the processes of tillage. This
has led to a strong belief among older farmers that " fer-
tilizers will run out the soil." The present tendency
among potato-growers is to use much larger applications,
which supply an excess of soluble plant-food elements
over those removed in the crop.

Practice in the use of fertilizers was for many years
based on the theories of the famous German chemist Von
Liebig. He taught that plant-food must be returned to
any soil to equal exactly that removed in the crop. The
practical error in the assumption that the composition

116 TJw Potato

of a fertilizer for any crop is determined by the chemical
analysis of the crop itself is that it does not sufficiently
take into account the great natural stores of plant-food
in the soil, nor the biological conditions. The plant-food
needs of the growing plant at any time are not necessarily
based on its final composition. The presence of a par-
ticular number of pounds of an element in soluble form
somewhere among the millions of pounds of soil on an
acre is no guarantee that the plant roots will be able to
find and use it at the time when it is most needed.

Growers in specialized potato-growing regions like Aroos-
took County and the early truck potato section apply more
plant-food than the potato can be expected to remove in
the crop, in order to make certain that it will not have to
suffer for a lack at any time. The effect of this practice
is seen in the subsequent crops. In southern trucking
regions, the choice of the crop to follow heavily fertilized
potatoes is largely governed by its ability to make good
use of the fertilizer left by the potatoes. The longer ex-
perience of European farmers with fertilizers has resulted
in England in laws by which the value of the fertilizers left
in a soil by crops is computed. Under the tenant system,
by which most of the farms of England are worked, an
outgoing tenant must be paid by his successor for the
unused fertilizer left. This proportion of the value of the
fertilizers applied varies with different materials, being
lowest with the soluble nitrate of soda and highest with
such slowly acting materials as ground bone and lime.

MARKET FORMS OF FERTILIZERS

Commercial fertilizers are found on the market in the
form of manv different materials which are also manu-

Manures and Fertilizers 117

factiired into many branda of mixed fertilizers, usually
being prepared for some special crop or soil. Both the
materials and mixed fertilizers are sold under statement
of definite percentages of the plant-foods they contain.
Annual state inspection and analysis show that these
statements are usually reliable. Each has advantages
for farmers' use. The mixed factory goods are usually
in good mechanical condition for sowing and are generally
kept or can be soon obtained from dealers. These dealers
usually extend credit to buyers. The manufacturers
contend that by the wet or acid process they are liable to
utilize materials too insoluble for use directly by crops.
The many trade brands for the same crop may differ
greatly in composition ; and often a number of brands
having the same analysis are sold as "special fertilizers"
for widely varying crops.

The variation between soils is so great that the same
crop raised on different lands may require widely varying
fertilizers for the best results. Only experience and careful
study will show what these requirements are. Such study
and observation are rather rare in America. In Europe,
farmers are more accustomed carefully to mix their ferti-
lizers according to the special needs of each combination of
soil and crop. In Germany this goes so far that the mate-
rials are often applied separately at the most favorable time
for the action of each, although this would not be advisable
here on account of greater cost of labor. The materials
used by farmers in home mixtures are usually of high grade.
Sometimes, as with nitrate of soda, acid phosphate and muri-
ate of potash, a mixture that is of the right analysis for a
particular crop may be composed of materials that are
sticky in combination and do not drill well. Care must
often be taken to include materials like dried blood, tank-

118 The Potato

age, ground bone and sulphate of ammonia that drill well.
The cost of home mixing may be one dollar a ton, more or
less, sometimes under fifty cents. A tight wagon box or
barn floor, screen, measure and shovel are the only belong-
ings needed if enough is mixed so that batches are made
up of one or more bags of each material. If less, scales
are needed. Dealers do not like to sell materials in small
quantities, but by clubbing together farmers can buy car-
load lots.

Most of the phosphoric acid in factory-mixed fertilizers
comes from acid phosphate. The value is the same from
any source if acid treated. If not so treated, as in tankage
or ground bone, it is slower to become available. IVIost of
the potash comes from muriate and kainit, which differ but
little in their action ; some comes from sulphate. Fertil-
izers vary mostly in the value of the nitrogen. The higher-
grade factory-mixed fertilizers are more certain to have
high-grade nitrogen than the low-grade cheaper mixtures.

Before the great European war, the prices of fertilizers
had remained fairly constant for a number of years. The
experiment stations in the northeastern states usually
value the best grades of nitrogen at 15 to 18 cents a pound,
soluble phosphoric acid in acid phosphate and potash in
muriate at about 5 cents. These prices are ton lots of
the best materials bought for cash in large markets.
Buyers of car-lots usually purchase enough cheaper to
cover the cost of freight to country points at these prices.

Lack of knowledge of fertilizers among farmers has led
to a failure to appreciate the fact that it is the cost a pound
of the plant-food which the fertilizer contains and its
quality that determines the actual value of any fertilizer,
not the price a ton. Many farmers look too often at
the cheapest, regardless of the analysis. For example,

Manures and Fertilizers 119

muriate of potash contains four times as much potash
in a ton as kainit and often costs less for the one ton than
for four tons of the less concentrated material, making
the potash cost less a pound, in addition to the saving
in labor of hauling and applying. The cost a pound of
nitrogen in high-grade dried blood, nitrate of soda and
sulphate of ammonia at $50 to $70 a ton, may be less than
in the cheaper grades of tankage and the like, besides
being of far better quality.

There is less variation in the price a ton of acid phos-
phates because the best sold in America seldom exceeds
16 per cent. The relative cheapness of plant-food in
mixed fertilizers depends largely on the analysis.

Mixtures of acid phosphate and potash are compara-
tively low priced and at the same time are of high grade
and cheap for the amount of plant-food which they con-
tain. Nitrogen is so expensive that a small percentage
runs the price up rapidly. Usually the higher grades of
so-called "complete fertilizers," costing $30 a ton or more,
are relatively cheaper than lower grades selling around
$20 a ton. It is usual for the makers of the higher-priced
complete fertilizers to claim that the nitrogen in them is
in a variety of forms of varying quickness of solubility,
thereby becoming gradually available to the crop through
the growing season. This is something which should be
considered by farmers in making up their orders for
material for home mixing.

NITROGEN

Nitrogen helps rapidly to increase vegetative growth.
When nitrogenous fertilizers are extensively used, the
foliage grows large and rank and has a dark green

120 The Potato

color. In extreme cases the foliage may become too loose
and open and porous in texture, and so render the potato
plant more liable to the attacks of disease and sun-scald.
Lack of available nitrogen for the plant is shown by small
size and light yellow color of the foliage. Commercially,
nitrogen used in fertilizers comes from a variety of sources
which vary greatly in value and in the quickness with
which they become available. Nitrate nitrogen, the form
to which other forms must be changed in the soil before
the plants can take it up in the soil solution, is the quickest
available. Nitrate of soda is the principal commercial
form. It comes from deposits in Chile, hence the old
name of "Chile saltpeter." It is so rapidly soluble in
water that it may sometimes be dissolved and lost to the
plant if heavy rains fall before the feeding roots have had
time to form. For this reason, it is either applied after
planting as a top-dressing or is used foi" only a part of
the nitrogen of a mixture, the remainder being in slower
acting forms. Because of this rapidity of action, nitrate
of soda is particularly valuable for use in early spring, on
early potatoes before the soil warms up enough for the
processes by which the other forms of nitrogen change to
nitrate. It contains about 15 per cent of nitrogen. Sul-
phate of ammonia, a by-product of coke and gas manu-
facture from coal, is next in order of availability. It
contains the largest percentage of nitrogen of any material
— 20 per cent. It has good mechanical condition for
mixing or sowing. One drawback is that its use tends to
make land sour and that it is not very efficient on sour
soils. Nitrate of lime and cyanamid are comparatively
new commodities, being made from the gaseous nitrogen
of the air by the use of electricity. While not extensively
used, it is probable that in time they will become very

Manures and Fertilizers 121

important sources of nitrogen. Cyanamid is difficult to
mix well in fertilizers and has other drawbacks.

Much of the nitrogen of factory-mixed fertilizers comes
from organic sources. These are slower in their action,
as the organic forms of nitrogen must be changed first to
ammonia and then to nitrate before the plants can take
them up. Warm weather and warm soil are needed for this.
Dried blood is the best of the organic forms, with tankage,
fish scrap and cottonseed meal also used in different sec-
tions. Other more slowly available forms like leather,
animal bone and horn meal are nearly useless to the
potato crop unless treated with acid by the wet process to
make them more soluble. In comparing the prices of any
of these materials, the degree of availability must be
considered as well as the price a pound of the nitrogen.
It is unfortunate that state laws do not compel the state-
ment of the percentage of each of the principal forms in
which nitrogen is found in fertilizers as well as the total.
At present the nitrogen in as poor a material as dried peat,
oft(m used as a drier in mixed fertilizers, counts as high in
the total percentage of nitrogen as from nitrate of soda
or dried blood.

Nitrogen is so much more expensive than the other
elements of plant-food and so easily lost from the soil that
every effort should be made to conserve and increase the
soil supply by the use of rotations which provide plenty of
organic matter, including legumes, and by making soil
conditions as favorable as possible for the different soil
bacteria which take or change nitrogen. The other plant-
foods are in the soil in stable forms which are not easily
lost. Nitrogen exists largely in very unstable forms which
are easily lost in drainage water or b}'^ changing into the
gaseous form of nitrogen.

122 The Potato

PHOSPHORUS

Phosphorus, usually referred to under the name of its
form as phosphoric acid, or P2O5, is often in very small
quantities in American soils, even in those abundantly
supplied with other elements of plant-food.^ Its actions
on growth are not fully understood, but are very im-
portant and are becoming more and more appreciated.
A deficiency in soluble phosphoric acid quickly reduces a
crop yield. Unless a sufficient amount is present, plants
do not mature properly. Its use tends to produce early
maturity and is marked by dark green foliage.

The principal supply for use in fertilizers comes from
deposits in the South which are supposed to be derived
from fossil bones. When ground finely, this material is
sold under the name of "floats" or "raw rock phosphate."
It is much used in the corn belt states and gives good
results there on general farm crops. It is too slow-
acting for the more delicate potato crop, and has not given
very good results in most experiments in the colder north-
eastern states. Acid phosphate is made by treating this
raw rock phosphate with sulphuric acid. This unites with
part of the lime in natural coml)inations with phosphoric
acid. Instead of the insoluble jjhosphate in which three
parts of lime are united to each part of phosphoric acid,
there is formed the water-soluble form in which only one
part of phosphoric acid is united to each part of lime, to-
gether with a small proportion of the reverted form soluble
in weak soil acids in which two parts of lime are united
to each part of phosphoric acid. The sum of these makes
up the available r205. Acid phosphate is also made from
animal bones, but the supply is only enough for a small

' See Bulletins by Hopkins, 111. Agri. Expt. Sta.

Manures and Fertilizers 123

fraction of all that is used. Acid phosphate is the prin-
cipal source of phosphoric acid in this country, either for
factory-mixed fertilizers or for home mixing. The word
"acid" has created a foolish prejudice against its use which
is not warranted by facts. A very small application of
lime will prevent any chance of the soil becoming sour
from its use. Ground animal bone and basic slag are
valuable sources of phosphoric acid for some other crops,
but are too slow acting for the tender potato. Different
grades of American acid phosphates vary in the percent-
age of phosphoric acid from 12 per cent to 16 per cent or
more. Only the highest grades should usually be bought.
The price a pound of the phosphoric acid applied to the
land is the real cost.

In the northern states the price a pound at the rail-
road station is usually less in the higher than in the lower
grades and in addition there is the cost of hauling to the
farm and applying to the land. Three tons of 1(3 per cent
acid phosphate usually cost less than four tons of the
12 per cent and the cost of hauling and sowing the extra
ton is saved.

POTASSIUM

Potassium, usually referred to as "potash" or K2O, is
present in large quantities in most American soils. Some
of the very sandy soils near the seacoast and the swamp
mucks are likely to be deficient in it. Potash helps in the
translocation of starch within the potato plant and tends
to lengthen the life of the crop. Practically all the com-
mercial supply of potash comes from deposits in Germany,
controlled by a syndicate there. The principal form used
in America is that of muriate of potash containing 47 to 50
per cent of actual potash. This is usually the cheapest

124 TJie Potato

form in which to buy potash. The chlorine in the com-
bination with the potash has some tendency to make soils
sour, and in some experiments ^ has produced smaller yields
and poorer quality than when sulphate of potash was used.
The latter, 47 to 49 per cent potash, is more expensive and
is but little used except for tobacco fertilizers. Kainit is a
raw material of low grade (12 per cent potash), and is rela-
tively higher in price a pound of potash contained in most
places on account of the freight on material of less value.
Potash fertilizers are mixed in the soil after applications
and are not likely to be lost by leaching. The solutions in
soil water are rather caustic, and heavy applications are
likely to burn the roots of plants if applied close to the
seed. The old idea of mixing fertilizers according to the
chemical composition of the crop has led to the use of
fertilizers containing much more potash than practical
experience of farmers and scientific experiments warrants.
Mixed fertilizers often contain 7 to 12 per cent of potash.
A number of experiments by the Geneva and other agri-
cultural experiment stations have shown that this is too
high for profit. Five per cent is usually all that will pay.
Potash is so abundant in most American soils that nitro-
gen and phosphorus are likely to be much more needed,

CALCIITVI

Calcium, in the form of lime, is seldom so deficient in
American soils as to render its use directly necessary as a
fertilizer for potatoes. In fact, A^ery heavy yields of pota-
toes are often grown on soils too acid to grow clover. The
potato seems to be very tolerant of acid conditions. Heavy
applications of lime produce conditions under which the

1 Brooks, Mass. Expt. Sta.

Manures and Fertilizers 125

common scab is likely to injure the tubers.^ The
powdery scab prefers acid soils and is reduced by liming.
There are other reasons which make the use of lime of
great value. The other crops of a potato rotation are
more likely to be benefited than the potato, and the net
profit of the rotation as a whole must be considered. The
clover and grass crops are the ones most benefited by lim-
ing, and these are the ones that do most to maintain the
soil supply of organic matter. Heavy sods and other
residues from hay crops bring up soil fertility rapidly at
small cost. In this way subsequent crops of potatoes are
benefited. Lime is also essential for the action of the
beneficial soil bacteria. Many American soils are now
becoming deficient in lime. Lime should be added to soils
in rotation in which potatoes are grown to as large an
amount as the soil can use without producing scab on the
tubers. What this amount will be can be found only by
careful trial on every soil and sometimes on every field.
Some soils can use several tons of limestone to the acre
without danger, while 500 pounds might be too much on
limestone soils or those in high condition of fertility.
Burned lime has been almost the only source of lime for
many years. Ground limestone is now coming into use
very rapidly, and it is probable that before many years will
entirely displace burned lime in most places. It is much
easier to apply and its use is safer. Burned lime is thought
by some to have a tendency to use up the organic matter
in the soil, even when thoroughly slaked before application.
Hydrated lime is too expensive to compare with the
others. Any form of lime should be applied to the crop
in the rotation which follows potatoes, and should be
thoroughly harrowed into the soil.

' Vt. Bui. 184.

126 The Potato

SULPHUR

Sulphur is present in all soils and is not likely to be
deficient in any way. There is some ground for the belief
that part of the value of acid phosphate is due to the
sulphur contained in it.

APPLYING FERTILIZERS

The method by which fertilizers are applied to a soil
often determines the profit to be obtained from their use.
Nitrate of soda is so quickly and easily soluble in the soil-
water that it can be sown on the surface of the land at any
time with the certainty that the first rain will dissolve it,
or that it will quickly dissolve if mixed with the soil.
Other fertilizers require weeks, months or even years to
become available to plants.

A gradual evolution is taking place in the ideas as to
the proper use of fertilizers. In the earlier days of their
use, when the quantity applied w^as limited to perhaps
100 to 200 pounds to the acre, it was rightly considered as
only a starter for the young plants. It was applied to the
soil close to the seed, being often dropped by hand. The
roots starting from the young plants were certain to find
a supply of readily available plant-food as soon as they
could use it. This would give a quick start to the young
plant, which would enable it to grow more quickly to a
size when it would be able to forage for itself. As the
profits from the use of fertilizers became known, the
amounts gradually increased. About the same time
machine-planters came into use. These applied the
fertilizer in the form of a strip several inches wide in the
bottom of the furrow-mark. This wide-strip application

Manures and Fertilizers 127

is essential to prevent root injury. Application with the
planter works well whenever moisture is abundant in
the soil throughout the growing season in Maine. As the
amount applied to the acre increased to 1000 pounds or
more, growers began to use a wider distribution through
the soil. With such large amounts, there is no need of
specially placing some of it near the plants, as a fraction
is enough to act as a starter.

At the present time heavy applications of fertilizer are
used in the specialized potato-growing districts in this
country, with the idea of supplying so much that the grow-
ing plant will never suffer for lack of plant-food at any
time. For such amounts as 1000 to 3000 pounds to the
acre, broadcasting is coming into use in whole or in part.
Ordinary grain-drills or special broadcast fertilizer sowers
are used. All fertilizers broadcasted should be thoroughly
worked into the soil. While there is some tendency for
soluble fertilizer salts to work downward into the soil,
there is likely to come any summer, after potatoes are
planted, a hot and dry time when several inches of the top
soil is very dry. The fertilizer in such a dry soil is prac-
tically useless to the crop for lack of sufficient water to dis-
solve it. This is especially true when a surface mulch of
dry soil is maintained for the purpose of conserving the
moisture in the earth below. This accounts for some of the
contradictory results obtained by experimenters on com-
parisons of the application of fertilizers by the drill and
broadcast methods. Under the conditions of northern
Maine, in which the water in the soil is usually abundant,
part of the heavy fertilizer used is often put on after the
plants are up, being applied to the ridge and covered with
soil. It is doubtful whether this method would be a
success in other regions, even in some other parts of

128 The Potato

Maine/ unless soil moisture conditions are fairly certain
to be favorable at the time of the second application.
Nitrate of soda may be applied at any time, as it is so
easily dissolved. Success with any method of applying
fertilizer depends on soil moisture conditions. The correct
method in one case may be entirely wrong in another.

The writer has developed, for his own farm conditions,
a method which has been very successful for applying
large amounts of fertilizer. The soil is a silt loam of good
water-holding capacity, further increased by the incorpora-
tion of large quantities of organic matter. The total rain-
fall for the whole year averages under 30 inches. Periods
of dry weather after planting, sometimes extending to
several weeks, keep the surface soil very dry. In some
fertilizer experiments, acid phosphate applied as a top-
dressing after planting did not become dissolved to produce
much increase in yield. At the same time, when it was
applied deeper in the soil before planting, a good increase
resulted. The soil is deep, and potato roots easily pene-
trate to the depth of several feet. The fertilizer is usually
1500 to 2000 pounds of a mixture of acid phosphate and
muriate of potash.

Part of the fertilizer is sown broadcast in early spring
on the surface of fall-plowed land, thoroughly disked in to
the depth of 7 to 8 inches and the field replowed to the
depth of 10 inches. The remainder of the fertilizer is then
applied and disked in as before. The essential idea of this
method is to have a large amount of fertilizer so evenly
and thoroughly distributed through the soil to the depth
of 10 inches that the potato roots are drawn out and down
completely to fill this whole space, rather than to have a
tendency to remain in the more limited space occupied
1 Maine Agri. Expt. Sta. Bui. 246.

Manures and Fertilizers 129

by the fertilizer when either the drill or the broadcast
method of sowing is used. Scientific experiments show
that roots multiply mostly in the soil where the supply
of plant-food is most abundant.^ The surface mulch
of dry soil keeps the lower parts both moist and cool.
Later the heavy tops shade the ground with the same
result. This cool lower soil, although itself too dry for
roots to grow in, is a marked advantage in hot seasons in
preventing degeneration of the potato as well as in increas-
ing yield. 2

This method of applying fertilizers has produced very
striking results in dry seasons. In periods of extreme
drought the tops showed but little injury from tip-burn and
grew continuously. The writer thinks that this success
is due to the greater moisture supply made available to
the plants by the wide and deep distribution of the root
system. This enables the plants to find and utilize the
water in a larger volume of soil at the time when the
plants need it most. When the roots are encouraged
to develop near the surface by broadcasting the fertilizer
and working it in shallowly, the drying of the upper soil
layer deprives the plants of the use of much of their root
system, and may leave them in poorer shape to with-
stand hard conditions than if the roots had been forced to
spread out and down earlier to find plant-food.^ In the
corn-belt, dry weather in June is recognized as a favorable
factor for the future success of the corn crop because it
forces the plants to root deeply, while a wet June would
result in shallow rooting which would be certain to suffer
later in the summer.

1 Storer, " Agriculture." Vol. 1, pp. 297-300.

" Neb. Agr. Expt. Sta. Bui. 146 ; and Colo. Agr. Expt. Sta. Bui. 216.
' Bureau of Soils. Bui. 22, p. 52.
K

130 The Potato

FARM MANURES

Farm manures increase the productiveness of the soil
in four ways : first, by the actual plant-food added to the
soil ; second, by the physical effect of loosening and
aerating the soil and adding to its moisture-holding ca-
pacity ; third, by the action of the organic matter of the
manure in making available to the plants by its decay the
insoluble plant-food of the soil ; and fourth, by improving
the soil conditions for the work of the beneficial bacteria.
Any computation based on the trade value of the plant-
food may be falsified by the other values being even more
important. A better way is to consider the results ob-
tained in farm practice by particular crops through a
series of years long enough for the residual effect of the
manure on the soil to be measured. The potato usually
responds well to the use of manure throughout the humid
sections, and the increase in yield of a cash crop like the
potato gives quick returns for the use of the manure.

There is some danger that common scab will be worse on
potatoes grown on land heavily manured. This danger
is reduced by using smaller amounts, by having the
manure rotted, and by spreading some time before plant-
ing. Horse manure is thought by some to favor scab
more than other manures, but this is doubtful.

Manures are poorly balanced fertilizers. They contain
relatively much more of nitrogen than of the other
plant-food elements and are likely to produce plants
with large growth of tops without corresponding tubers.
This can be prevented by using with the manure 50
pounds of acid phosphate to each ton, and in rare
cases potash may be added also. Coarse and strawy
manure may make some soils too open and porous,

Manures and Fertilizers 131

causing them to dry out, particularly in dry years and
dry climates.

A practice in handling manure that is gaining ground is to
apply it to the hay crop preceding potatoes in the rotation.
By increasing the yield of the hay, the organic matter left
in the soil by the roots, stubble and aftermath is increased
for the use of the potatoes later. When manure is applied
directly to the potato crop, it is better spread in the pre-
vious fall or winter than just before plowing. The manure-
spreader does better work than hand-spreading because of
the practical impossibility of getting as even distribution
with a fork as wdth the machine. Unless the potato-
grower has only a small area, it is more profitable to give
the whole a thin coat of manure than to have parts heavily
covered and the remainder without any. Experiments
extending over many years show that the profit to a ton
decreases as the size of .the application increases. The
manure-spreader has an advantage over hand-spreading
in this respect because smaller amounts to the acre can be
spread evenly.

The value of farm manure is greatly reduced by poor
methods of handling. The best net returns from its use
come from spreading as soon as possible after it is made.
When necessary to keep it for some time, as when fields
are occupied by growing crops in summer, precautions
should be taken to prevent loss. Exposure to rains may
leach away half the value in a short time. By heating in
piles, much of the nitrogen escapes. Keeping under cover
prevents leaching. Keeping in shallow^ piles, tramping by
animals and occasional wetting prevents heating. Land
plaster and other substances are mixed with the manure
to prevent the loss of nitrogen. Raw rock phosphate
or " floats " is valuable for this purpose in addition to

132 The Potato

its phosphoric acid, the element needed to balance the
manure as a potato fertilizer. Acid phosphate is valu-
able for this purpose, but it must not be used under the
feet of animals. Manure spread in the winter suffers no
loss from heating and but little from leaching unless the
field is so sloping that water runs off rapidly. It is so
difficult to prevent loss in manure kept in other ways
that spreading as rapidly as made is the best method in
most cases.

REFERENCE

VoELCKER and Hall. The Valuation of Unexhausted Manures.

CHAPTER VII

PLANTING
By Daniel Dean

Soil preparation for planting potatoes should be such
as will meet the peculiar demands of the potato plants.
A loose and mellow soil is needed for extension of the weak
and tender roots and for the development of the tubers.
Preparation should be designed to correct the faults
of the local soil and climate as far as that can be accom-
plished. Preparation before planting should be such as
will reduce the tillage after planting as much as possible.
Weeds are more cheaply killed by wide-spreading tools,
like harrows and disks, than by small, single-row tools
or by hand hoeing later.

Fall plowing is of great value in all but the lighter
soils. It rots the soil organic matter, puts the land into
better physical condition by exposing the bare soil to
winter freezing, stores up more water for the use of the
crop and sprouts and kills part of the weed seeds in the
ground. The control of insects, like the white grub
and wire-worm, is easier with fall plowing because the
larvae are more exposed to freezing and to attacks of
their natural enemies, such as birds. As a rule, the
heavier a soil, the more it is benefited by fall plowing.
There is some saving in labor by fall plowing in the
northern states because potatoes are usually followed
133

134 The Potato

by spring-sown grain, which requires considerable work
early in the spring. The harrowing needed to place
fall-plowed land in condition for planting takes less
time than spring plowing and the harrowing necessary
to cut up the sod well. Harrowing must be deep and
thorough or the benefit of fall-plowing may be largely
lost. While there is some additional loss of moisture
from plowing a second time in spring, this later plowing
greatly reduces the amount of harrowing necessary and
makes certain that the soil is well pulverized to the
depth of the furrow. It is well to fall-plow land as
roughly as possible wdth the furrows-slice standing nearly
on edge. A rough surface catches the rains better, ex-
poses the soil better to the action of frosts and reduces
the damage by winds through the winter. Water is
saved in fall-plowed soil because the layer of sod or
trash at the bottom of the furrow prevents the water
in the subsoil from escaping as readily. Straw or manure
spread on the surface before fall plowing will usually
become rotted enough by spring to give little trouble if
replowed. The mellow soil with rotting organic matter
holds more water than unplowed land would, especially
in places like dry knolls. Clover sods rot quickly, but
sods of the grasses take longer. With spring plowing
only, it is beneficial to cut up the grass sods with a disk
harrow before plowing. The sod rots more quickly and
the soil settles together better so that the movement of
the water in the soil is not hindered.

Earliness is a great advantage in spring plowing in the
northern states. An experiment by King at Wisconsin
showed that water equal to If inches of rainfall was
evaporated in one week in spring. Water evaporates
from the soil very fast in the first days of spring after

Planting 135

the frost goes out. This water can seldom be fully
replaced by later rains. Its conservation may often
turn the scale between success and failure in droughts
late in the season. Fall plowing has here an advantage
over spring plowing because it is possible to cover many
acres with harrow or disk in a few days as soon as the
ground can be worked without injury in the spring.
By going over fall-plowed potato ground once before
sowing spring grain, the saving in moisture for the potato
crop will more than pay for any loss of grain by slightly
delayed sowing.

TILLAGE TOOLS

The plow is the standard implement of tillage. Ex-
cept in special cases, nothing has been found to equal
its work. The common plows used in the East and
South are drawn by one, two or three horses or mules.
The two-bottom reversible sulky plow is coming much
into use in the East. It is heavier and more expensive
than the common plow, but will work better in soils of
varying hardness, and in plowing alfalfa sod. This
reversible sulky plow, like the ordinary two-bottom gang
sulky used in the central West, does poorer work in plow-
ing mider straw, stalks and the like than the ordinary
walking plow. The plow can turn under sods, and so
forth, more perfectly than any other tool, and its use
distributes surface organic matter. The jointer enables
sod and trash to be buried more completely.

The type of harrow to be used depends upon the work
to be done. Harrows may be used merely to fine and
smooth a rough surface, like the spike-tooth harrow, or
may be designed to tear up and fine the soil to consider-
able depth, like the disk and spring-tooth types. The

136 The Potato

disk and its variation, the cutaway, are used most in
soils nearly or quite free from stone. With these the
soil can be thoroughly fined nearly to the depth of the
plowed furrow. The disk will cut up sods or straw and
will work in soils so full of weed-roots that other types
of harrows will be clogged. The spring-tooth harrow is
used more than the disk in sections with stony soils. It
pays to keep the cutting edges of the disk or the points
of the teeth sharp. The spike-tooth smoothing harrow
should follow the disk to level the surface before plant-
ing. It is also valuable to keep a surface mulch before
planting and to kill weed seeds that have sprouted.

The roller is a tool of great value, but is often used
with poor judgment in potato-growing, because it has
considerable weight for the small surface. Its action,
resting on the soil, is to firm the earth to a considerable
depth, something seldom necessary with potatoes unless
on very light soil, and is often harmful. Used to follow
the plow after plowing in the spring, it may help to pre-
vent sods on edge from making open spaces in the soil.
Too often it is used with the idea that it is necessary,
as with the grains and grass seeds, to firm soil around
the seeds to furnish moisture for germination. The
roller is used to assist the germination of grain and grass
by packing the soil around them, causing it to become
damp by the capillary rise of water. Such seeds are
dry and need water to start, and their small size demands
closely packed soil for the benefit of the roots. Unlike
the dry grain seeds, the large potato seed-pieces have all
the water they need, 80 per cent, and can grow for weeks
without any from the soil. This fact is familiar to those
who have seen potatoes in cellars send shoots to the
length of several feet. Soils are seldom too loose for the

Planting 137

potato and are very often too hard. The plank float,
or clod crusher, is a better tool to crush lumps, and does
not settle the soil below the surface as does the roller.
Such lumps crush easiest a few hours after a rain.

The depth of plowing for the potato should be as great
as the fertility of the soil will permit. The weak potato
roots need all the space they can get. Outside of the
arid regions of the United States, care must be taken
not to expose much of the cold and infertile subsoil at
any one plowing. Where it is necessary to plow land
deeper than formerly, not over one inch of subsoil should
be turned up at a time. Organic matter must be added
to lighten the subsoil turned up, as it is very deficient in
this. Sandy soils, in which potato roots penetrate easily,
need deep plowing less than heavy soils. Only three to
five inches is used in some sandy sections. Heavier
soils, if well provided with humus, are frequently plowed
to the depth of ten inches or more, usually about 6 or
7 inches.

RESULTS OF TILLAGE

The results of soil tillage are :

(1) The organic matter in stubble, manure, and the
like is buried in the soil, to decay there.

(2) The mineral particles are made finer, and fresh
surface exposed to the action of solvents, such as soil
water and carbonic acid.

(3) The soil organic matter is broken up and easily
changed into more useful forms. The rapidity with
which soil organic matter is destroyed by tillage is
little appreciated. The common saying, that "tillage
is manure," is practically true. Tillage is expensive in

138 The Potato

labor and also expensive in the changes it produces in
the soil. A soil thoroughly tilled for a potato crop has
thereby lost a considerable amount of organic matter.
The expense of replacing this must be considered in the
final profit-and-loss account of the crop. In many parts
of the United States, potato-growing has gained a bad
reputation from the rapidity with which it reduces the
fertility of the soil. In others, where organic matter is
kept up by good rotation and where fertilizers are used
heavily, potato-growing is regarded as a sure way to
enrich the land, A single tilled crop, like potatoes or
corn, places the soil in better physical condition to grow
succeeding crops of grain and hay. The alternation of
tillage crops, which excite and increase bacterial activity,
with the hay crop will provide organic matter as a food for
the bacteria and thereby keep up fertility at low expense.

(4) The increase of the volume of the air-spaces of the
soil by thorough tillage greatly increases the chemical
and bacterial activities of the soil. The oxygen of the
air combined with the organic matter of the soil causes
the formation of carbon dioxide. This, in turn, acts
with the soil water as a solvent of mineral compounds,
such as insoluble phosphoric acid. The beneficial bac-
teria of the soil are favored by plenty of air in the soil
and increased greatly in number and activity. Their
action increases the availability of the soil plant-food.
Some species of soil bacteria are injurious. As these
mainly thrive where little or no air is present, tillage re-
duces their effect.

(5) Tillage exposes fresh soil surfaces to the air and at
first causes some loss of moisture. Loosening the surface
soil by tillage prevents evaporation from the lower parts
of the soil by breaking up capillary connection between

Planting 139

the soil under the tilled area and the surface. Until
capillary action is again established by the settling to-
gether of the tilled soil, but little water can be lost by
evaporation. A thin layer only of loose soil is sufficient
to prevent evaporation. A thin layer settles together
sooner than a thick one and needs breaking more often.
More emphasis has usually been placed on tillage of
potatoes after planting than before planting. The
great soil supply of water in late winter and early
spring presents opportunities for conservation that exceed
those during the growing period of the crop. In recent
years a change has come about in the attitude of inves-
tigators towards the value of summer tillage. Extended
experiments have shown that one factor which was
largely neglected by early experimenters is of impor-
tance — this is the ability of the plant root to seize
upon the use of soil moisture. When the soil is not
occupied by a growing crop, there is no doubt that a sur-
face mulch of loose soil does conserve moisture by pre-
venting evaporation, but when the soil is well filled with
plant roots, there is little more water evaporation from
untilled soil than from tilled. The gains in yields ob-
served from tillage come from another source — weed
killing — rather than from prevention of the evapora-
tion. This means that the farmer will till practically
as much as under the former practice, but will have in
mind weed killing as his principal object, instead of pre-
venting loss of water. In practice this will mean that the
tillage of the potato crop during the growth of the crop
will be done earlier than has been the custom. Water
will be conserved by fall plowing where possible ; by the
addition of organic matter to the soil ; and by early spring
tillage to save the water supply. The soil will not be

140 Tfie Potato

allowed to dry out for the late main crop of the northern
states before planting. All this early tillage also kills
many weeds which have formerly been left to be killed
by inter-tillage later on.

After planting there is a period of several weeks when
large and wide tools can be used to advantage in tillage.
The harrow, leveler and weeder cover several planted
rows at once and kill weeds very cheaply, besides saving
moisture.

The necessity of weed killing for the production of
large crops is even greater than the saving of moisture
by tillage. Weeds not only rob the potatoes of mois-
ture, but are able by their stronger root systems and
greater foraging ability to seize upon and use the soluble
plant-food in the soil. Very small weeds in this way
injure the potato crop more than would be supposed.
The weeds which sprout from seeds in the soil are more
easily killed before coming up than afterward. The
tender shoots from the seeds are killed by a light stirring
of the soil which would not affect them at all a few days
later. The sprouts starting from the seed have but little
vitality until they can reach the surface, and produce
green leaves. Then roots start to secure plant-food which
is worked by the leaves into material for further growth.
Every day now adds to the ability of the young weed to
stand punishment and live. Several successive crops of
weed seeds can be sprouted and killed by tillage between
planting and the time when the potato tops are six inches
high. Tillage at this time can be done carefully enough
to prevent injury to the growing sprout of the potato
before it comes up and until it is established for itself
in the soil. Perennial weeds with root stalks, like quack
or witch-grass, are much easier controlled by previous

Planting 141

cultivation in the fall or early spring than by tillage during
the life of the potato. The reserve of nourishment in the
root stalks enables them to stand punishment for several
weeks and recover from it to injure the potato after
tillage is no longer possible.

The preceding results of tillage have all been favorable
to the potato plant. Tillage has another action which
has not been sufficiently studied and which has led to
many conflicting results in experiments and in farmers'
practice. It is a fact that tillage can injure the potato
plant even easier than it can the tough and hardy weeds.
It is very difficult to work with soil near the potatoes
without injuring them. As the season advances, this
becomes more dangerous to the potato. While the
young plant is still attached to the seed piece and draw-
ing on it for nourishment, it can lose part of its small
roots without great loss, particularly as the weather is
yet cool and favorable to the vitality of the crop. Each
day the potato grows older increases the danger of loss of
yield from injurious root injury. In the later part of
the plant's life, the whole upper soil becomes filled with
roots. These come so close to the surface that it is most
difficult to work any tillage tool without some injury.
Few tools except the hand hoe can be worked as shallow
as one inch, and many of the larger roots are that close
to the surface. Under some conditions, late tillage may
do less injury to the potatoes than under others. In
periods of abundant rainfall, the plants may tend to
root too close to the surface and some root-pruning may
force the potato to root deeper. If drought comes later,
this will be a benefit to the crop. In very cool seasons
in which the potato does not suffer from extreme heat,
root-pruning by tillage tools does less damage than in

142 The Potato

hot and dry seasons. The loss in yield from tillage at
the wrong time, too deep, or too close to the plants,
often amounts to a large percentage of the crop. The
greatest danger from excessive tillage is likely to come
in the northern states in which late cultivation of the
main crop comes at the hottest time of summer. When
the "critical period" of the plant's life comes at the
time when climatic conditions are most unfavorable to
the potato, any injury to the roots is likely greatly to
reduce the yield.

PLANTING

The time of planting depends on the market for which
the crop is grown and the local soil and climate. The
higher prices received for extreme earliness in the south-
ern truck crop compel the use of short-season varieties,
like the Triumph and Cobbler, and planting very early
to get the crop on the market before prices fall. All
cultural methods are arranged with this end in view, so
there is little choice in the time of planting. Along the
Canadian border and in much of the Rocky Mountain
section the whole growing season is but little longer than
the life of main-crop varieties. But in most of the prin-
cipal growing states, from New England to Iowa and
Nebraska, it is possible to vary the time of planting
by several weeks. Here, as a rule, most potatoes are
now planted in late May and in June. The later plant-
ings yield better because the crop matures in cooler
weather than with early planting. Moisture is more
likely to be abundant in fall than in late summer. The
dangers of late planting are late-blight and rot, — unless
spraying with bordeaux is practiced, — injury from early
frost and early fall freezing of the soil, and conflict of

Planting 143

the later tillage of the crop with the rush period of
haying and harvesting. But increasing competition of
the southern crop is forcing many growers to abandon the
previously profitable early crop for local trade. Bordeaux
spraying has been found to lengthen the life of the potato,
and potatoes to be sprayed may be planted slightly earlier
than those unsprayed, for that reason.

The methods of ridging and level culture with deep
and shallow planting are best illustrated by their use in
two of the best-known potato-growing regions of the
United States. Ridge culture with comparative shallow
planting is used in Maine. The northern latitude of
Maine makes the growing season short compared with
the southern states. The mean temperature of the
month of July is only 62° to 65° F. Frosts are frequent
in June and September and may occur in August. Not
much field work can be done before the month of May,
and October 10th is regarded as the danger line beyond
which potatoes are likely to be frozen in the ground.
Only a short distance away in the Atlantic Ocean, the
cold ocean current from the Arctic reaches the warm Gulf
Stream. The fogs of the fishing banks here are well
knowm. The rainfall is heavy and is seldom deficient
throughout the growing season. The rainfall of winter
is largely available to the potato crop. The ground is
covered with snow all winter and the loss by run-off and
evaporation before time of planting is much less than
that of the other great producing states. The soil con-
ditions of Aroostook County, the great potato-producing
section of Maine, are favorable for the retention of soil
water. Most of that section has been cleared from the
forests only a few years, compared with the longer settled
communities, and the soil is well supplied with organic

144 The Potato

matter. The region is so damp that the higher and
dryer parts are usually considered safer and better for
potatoes than those lying lower. The more or less
gravelly limestone loam soil crumbles Easily and seldom
gives trouble by baking. With such conditions under
which surplus of water is more to be feared than a de-
ficiency, Maine growers use an extreme ridge culture.
Instead of leveling down the ridges left by the planter and
depending mainly on the use of leveling tools and the
weeder to kill the weeds sprouting among the plants in
the row, Maine growers kill the weeds in the row by
ridging several times. There is little danger that the
growing plants in the ridges will suffer from lack of
moisture. Ridge culture is also the favorite in the ad-
joining provinces of Canada, in which conditions are
similar. This culture is suited to wet climates and
wet seasons. Digging is rendered easier by ridging
where the soil is likely to be wet. The first ridging after
the plants come through the ground covers the small
plants and prevents injury from*late frosts. In many
other sections, such covering would result in baking
the soil. Ridging is necessary under the methods of
irrigation in order to prevent injury to the potato plants
from the irrigating water.

Long Island potato-growing stands as an example of
prosperous farming, where a different method than the
ordinary is used. The soil of Long Island is a rather
light sand which is easily tilled and dries out quickly
after rain. Level culture is used because much better
yields are secured than by ridging. Less soil surface is
exposed to evaporate water by level culture.

Partly owing to the high prices in late summer, Long
Island potatoes are planted as early in the spring as the

Planting 145

ground can be worked — last of March and April —
and mature in the dry weather in July and August.
Deep planting and level culture exposes less of the easily
heated sandy soil to the sun and reduces danger of heat
injury as well as that from drouth. The light soil usually
is dry at digging time, gives little trouble in digging,
though sometimes fields left late before digging are
ridged to kill weeds which have started. Level culture
is a relative term as some earth is thrown toward the
plants by the teeth of the cultivators. This prevents
the growing tubers from being sunburned. Deep plant-
ing allows the soil over the rows to be thoroughly worked
in the week subsequent to planting. Weeds are easily
killed at this time and soil water conserved for the later
use of the crop. As a rule, early planted potatoes should
be put in shallower than late potatoes, as the sprouts
start more slowly in the cooler soil. Very shallow plant-
ing is seldom advisable unless the soil is so wet and cold
that heavy ridging is necessary for drainage. Growers
in other sections of the country use methods between
the two extremes, according to their conditions. The
truck crop of the South is raised under soil conditions
similar to those of Long Isfend. The need of securing
warmth in the soil to hasten growth leads to some ridg-
ing. Shallow soils with hard-pan close to the surface
as in the volusia soils of New York, Pennsylvania and
Ohio, present a hard problem. Ridging is the usual
method used in this section on account of trouble in digging
in wet seasons, and with the usually stony soil, it is diffi-
cult to control weeds near the plants by the use of other
tools than those which ridge the rows. Light and dry
soils particularly, if likely to be fairly dry at digging
time, do better with nearly level culture.

146 The Potato

The advantages of having sufficient soil over the seed
to permit wide tillage after planting are so great that it
pays growers to plant deep enough for this purpose.
The bottom of the furrow made by the planter or marking
tool should be at least two inches below the level of the
surface of the soil and better three or four; for sandy
soil likely to be dry, even more. Growers are often
deceived at the depth they plant by looking at the depth
of the mark below the level of the earth thrown out by
the marking tool instead of taking the measure from the
true level of the surface soil to the bottom of the furrow.

Hill and drill 'planting

Two principal methods of planting are used in the
United States. Potatoes are said to be in hills, checks
or squares when the ground is marked both ways and
the seed dropped at the intersection of the mark. This
method is much used for hand planting. It has the
advantages of permitting cultivation both ways and
so weeds are easier kept under control. With poor soils
the large area allowed to each hill is an advantage, as
each hill has enough space to produce a good yield. Rows
in the United States are from 30 to 42 inches apart ac-
cording to the value of the land, the amount of stone in
the soil and according to the fertility. Unless the ground
is very poor, it is advisable to have the hills closer to-
gether in the short way of the field to give a large yield.
Whew planted in drills, the seed is planted from less than
12 inches apart in the row in the best soils, to sometimes
nearly 2 feet in poor soils. Planting in drills is rapidly
gaining ground in the United States, as the yield from
the larger number of hills is larger to the acre than when

Planting 147

planted in hills. Growers in all the important potato-
growing sections find it practicable, by modern tillage
methods, to keep weeds subdued in drills as well as in
hills. The prices received for potatoes from sections in
which drill culture is general are higher than from those
where hill culture is mainly used. City markets demand
medium-sized tubers, and pay better prices than for the
coarse and overgrown tubers raised in hills. When
machine diggers are used, digging costs the same when
either method of planting is employed. With hand
digging, the larger number of hills to the acre under drill
culture takes more time to dig than with hills and may
reduce the acreage by limiting the amount which can be
dug before freezing weather. The constant improvement
in the manufacture of diggers is producing machines that
will dig in very stony soils.

The general rule for spacing hills is to vary the number
of hills to the acre according to the yield which may be
expected. As the distance apart decreases, the weight of
the individual hills and the size of the tubers is reduced
and the total yield to the acre is increased. The cost of
planting and digging may be increased. Digging close-
planted hills is rather expensive. The smaller size from
close planting brings higher prices in city markets. An ex-
treme case of close planting is that in the island of Jersey
where potatoes are planted 12 by 16 inches, or over
32,000 hills to the acre. With very rich soil and hand
tillage, a yield averaging over 400 bushels to the acre is
secured, even when dug for the early market, while still
growing. The ty^Q of the potato variety affects the
spacing. The common Rural or Blue Sprout type sets
fewer tubers to the hill than the Green Mountain or
White Sprout type and should be planted closer on that

148 The Potato

account to prevent coarseness, a common fault complained
of by city buyers in Rurals. Early types like the Bliss
Triumph and Irish Cobbler are usually planted closer
together than late varieties. In Europe it is a common
practice to use small tubers uncut for seed. These are
often secured by planting very close, sometimes as little
as six inches apart in the row. As before noted, wide
spacing allows faster digging on stony soils. Regions
of intensive potato-culture, such as Maine, Long Island
and the coast-trucking region, usually plant rows 30 to
36 inches apart and the seed dropped 12 to 16 inches
apart in the rows or 12,000 to 16,000 hills to the acre.
Regions with stony soils, as the Steuben County and
Chateaugay sections of New York, plant to some extent
in checked hills about 3 feet each way or less than 5000 hills
to the acre. The regions where the expense for rent of
land, fertilizer and care are high use close planting, while
low-priced land with other small expenses allows more
space to each hill, which may be of value in bad seasons.

Planting tools

Machine planters of several types are in use and a
larger proportion of the total crop is planted by machinery
each year. Hand planting is used mainly in stony and
rough sections, in the South where the labor is cheap and
not well adapted to using machinery and to sections
and farms where potato-growing is of small extent and
regarded as secondary to otlier farm crops. INIachine
planters are nearly universal in such regions of intensive
potato culture as northern Maine and Long Island.

IMachine planters are of two types. In one the seed
is picked up from a hopper and dropped by revolving

Planting 149

pickers ; in the other the seed potatoes are fed on a plat-
form containing a revolving wheel. An assistant to the
driver sits behind this and corrects the mistakes of the
planter by removing the extra pieces where two or more
are fed between pairs of spokes and by filling the spaces
which are empty. The first requires only a driver, an
advantage where labor is scarce. The picker type does
fair work Avhere the seed planted is small and round,
and on smooth land. Its efficiency falls off with the use
of cut seed and on rough or stony land. The picker may
injure the seed and spread disease. Picker planters are
most used where land is cheap and labor high, where
cheap cull seed is used wdth mellow soil and in general
where it is the object to raise large areas at low expense.
The platform type planter is adapted to higher priced
land where every missed hill is expensive. It will feed
cut seed perfectly with much less trouble to the feeder
if care is taken to cut the pieces somewhat blocky in
shape. With expensive seed and wfien spraying, manure
and fertilizer add to the acre cost, it does not pay to
have any missed hills to cut down the income from each
acre. The cost of each acre is the same whether every
hill is planted or not and the cost of the wages of the
second man on the planter is small compared with the
increased income.

The use of machine planters has called attention to
several advantages in their use which may be copied
with profit by growers planting by hand. The saving in
cost of labor over hand planting may or may not be great
when the cost of the machine is considered. The gain
from the use of machine planters is largely in other ways.
The machine opens the soil with a small plow or disk
and the seed is dropped into soil which is cool and damp.

150 The Potato

There is no tendency, as is often the case with hand
planting, for the seed to become dried out before cover-
ing. In some sections as on Long Island there is trouble
with seed slightly infected with late-blight germs rotting
in the ground after planting. Trouble of this kind is
much worse where furrows are left open and the soil
warmed to a temperature at which the blight germs
develop and rot the seed. Seed which becomes dried out
before or after planting seldom produces as good a yield
as where it is allowed to keep all its moisture. The seed
planted with the machine planter is put in to a more uni-
form depth than seed in rows dropped by hand which falls
on each side of the center of the row and forces the culti-
vator teeth to be kept away on account of injury to the
plants which are set out of line by hand planting. The
seed dropped by a machine falls in a straight row which
is less liable to injury from cultivating tools than that
dropped by hand. The weeds growing next to the plants
are the ones hardest to kill, and a perfectly straight row
easily kept clean reduces the damage from weeds. It is
uoticed that in sections where machine planters are in
common use the rows are usually planted close. The
soil in the space between the rows is so tramped by horses
and wheels of tools that it is of less value to the crop
than that in the row. The yield is increased by a larger
number of rows to the acre. Planters are often furnished
with a fertilizer attachment which applies the fertilizer
along with the seed. The fertilizer should be dropped
in a strip several inches wide and covered with soil before
the seed is dropped or the sprouts may be injured by
the action of the dissolved fertilizer salts.

Planting 151

Hand planting

More potatoes are planted by hand than by machines.
If well done, hand planting can be made nearly as good
as machine planting in some respects and far better in
others. It is scarcely possible to make a row as straight
and in as perfect a line as with a machine, and in prac-
tice the seed and soil must be exposed to drying for a
short time at least. The objection is often made that
machines cannot be made to plant deep enough. Much
hand planting is too shallow because the tools used in
marking the rows do not make the marks deep enough.
The three or four point markers used in many sections
cover ground fast, but the marks are very small. In
light soils these markers can be shod with iron points
large enough to make a fair mark. In heavier or stony
soils a small landside plow, or better a wing shovel plow
such as is often used for ridging should follow the marker
to deepen the furrows. All marking tools should be run
with great care to keep the rows straight. Crooked
rows result in damage to the potato plants by the culti-
vator teeth later in the season. Opening the furrows
just ahead of dropping, and covering right after, reduces
the danger of drying out seed and of warming the soil
too much. Covering the seed may be done with the hoe
or with a small plow, with a shovel plow or "middle
buster" in the South or with a hiller with wings on each
side of the row. With shallow soils the hand hoe does
the poorest work, as there is not enough earth placed
over the seed to allow tillage with harrow, weeder and
the like. Seed covered with the hoe in deep soils allows
such tillage to gradually fill up the mark, at the same
time killing many weeds. It has a great advantage for

152 The Potato

early potatoes in heavy soil, as the amount of earth covered
over the seed is so small that the plants come up much
quicker in cold springs than where several inches of dirt
are ridged over the seed.

SEED POTATOES

The problem of conserving the full vitality of the seed
potato until planted is a hard one unless cold storage is
available. The white sprouts formed in ordinary storage
cellars rapidly reduce the vitality of the seed, are easily
broken off and cannot be planted. The potato requires a
resting stage for some time after maturity, after which it
starts the sprouts rapidly at temperatures as low as 50° F.
If the temperature of the storage space can be kept down
to from 34° to 36°, the sprouts will not start and the whole
strength of the seed will be saved to grow the crop. Every
attention should be given in early fall, winter and spring
to keep the temperature down. Keeping the doors and
windows open on cool nights and closed daytimes in
fall and spring and using ice to keep down the heat re-
duces the sprouting. Potatoes intended for seed in
cellars sprout less in shallow piles on the floor than when
piled up too near the ceiling, owing to difference in tem-
perature. A special cold-storage plant would be ideal
but is too expensive for farmers unless for very large
growers. A very good method of storing seed which is
falling into disuse is that of storing in pits covered with
alternate layers of straw and earth to prevent freezing.

A European practice which may in time be adopted in
America is that of greening seed. The high cost of land
in Europe, low cost of labor, large proportion of small
tubers in the varieties grown, vigor of small tubers which

Planting 153

makes them safe for use as seed, use of immature seed,
and trouble with seed germinating, have led to the use
of a method of care of seed by which it is kept in winter
and spring in shallow trays racked up in buildings so
constructed that each tuber is in the light. The sprouts
at the seed ends start and grow short, green and stubby.
When planted, these potatoes start quickly and grow
rapidly. The cost of the equipment and of the labor
required to place the seed in the racks and again to place
the seed in the ground with every seed end up, would be
very heavy in America. Unless seed which has been
sprouted in this way for some time is planted with the
sprouts up, there is trouble in loss of stand. A modifica-
tion of this plan may be used, however, for American
conditions of cost of labor. Such short green sprouts
grown in the light for a short time, perhaps two weeks
or less, will not be broken off in a potato planter and will
give no trouble about coming up. It is, therefore, prac-
tical to keep the seed on a barn floor in the sun for that
time and save the strength of the sprouts which would
be lost by growth in a cellar. For a few days the seed
may be left in crates in the sun without making too long
sprouts in the crates.

Wlien seed potatoes are disinfected with formaldehyde
solution for common scab or with corrosive sublimate
solution for both rhizoctonia and scab, the crates may be
disinfected at the same time by having a vat of solution
in which the crates of seed are immersed. Soaking too
long or in too strong solution injures the vitality of the
eye. The seed must not be cut before soaking and must
be dried at once or rot may result.

The above-mentioned plan is much used in Europe to
plant tubers from \\ to 2\ inches in diameter without

154 TJie Potato

cutting. Trouble with soil diseases affecting the stand
is causing the use of similar small seed in some of the
western potato-growing sections. The use of small culls
as seed is usually condemned in the United States. Very
often the vitality of the cull seed is low on account of
disease or degeneration in the parent hill. Many experi-
ments have generally resulted in higher yields from use
of large seed cut than from small uncut seed. Even if
the small seed is used on part of the field on account of
the lower cost, it will pay growers in the northern states to
have seed plots in which large cut seed is planted. While
the results of the many experiments of the cutting and
size of seed are often conflicting some general rules may
be stated : —

(1) The yield to the acre increases with the size of the
seed piece up to 50 or more bushels of seed to the acre
when the distance of planting is the same.

(2) The yield to the acre increases with the size of the
fraction of the seed tuber from one eye up to the whole
large tuber.

(3) The net yield to the acre above the amount of seed
planted and the increased value of seed potatoes kept till
spring compared with an equal number of bushels on
increased yield which must yet bear the expense of digging,
storage and marketing, reduce the size of the most profit-
able seed to plant to much smaller size.

(4) Increasing the number of hills to the acre to-
gether with the amount of seed used, while keeping
the size of the seed constant, increases the total yield
and reduces the yield of the individual hill and the size
of the tubers.

(5) Cutting the same weight of seed to an acre into
smaller pieces may or may not increase the yield because

Planting 155

the seed will, at some size, be cut too small to insure a
good start to the plants.

(6) As noted above, salable tubers used as seed usually
outyield cull seed, because of the fact that a larger portion
of the culls come from weak, diseased or degenerate hills.
The cull is not poor seed because small, but because there
is a greater chance that its inherited vigor is low. In
cool and wet climates, like those of Scotland, Ireland,
and Maine, there is less risk of small seed being injured
in vigor than in climates too hot and dry for the best
growth of the potato. The use of the systems of field
seed selection to find the strain having the greatest
inherited vigor with seed plots to multiply the selected
seed produced a stock of which the small culls may be
saved for use as seed.

Experiment stations have found conflicting results in
studying the relative value of eye in different parts of the
tuber, which need further investigation. The eyes at the
seed end of the tuber start first to grow and are practically
the only ones which grow under greening in the sunlight.
When these seed-end eyes start sprouts, which are broken
off in handling before the others start the vigor is likely
to be more equal. Observations indicate that the eyes
nearest the stem end, particularly with varieties having
few eyes as the Rural type, are the ones most likely to
fail to grow and are the ones from which degenerate
strains originate. Under the present state of knowledge
of the subject, it is safest for growers to cut seed in such
ways as to have the seed end eye on as many of the cut
pieces as possible, and to allow a slightly larger amount
of flesh to the pieces with stem end eye, to make up for
their slower starting growth in spring.

Smaller seed pieces can be used with fertile soil than

156 The Potato

with poor soil. The young plant can become established
and get its nourishment from the soil quicker.

Whole seed matures the crop a few days earlier, an
advantage for early high prices, and is less likely to rot
in cold weather, and to attacks from soil diseases, as in
Colorado.

Cutting seed

Many tools have been invented for cutting seed potatoes,
but none is able to do as good work as the knife, eitht r
in the hand or fastened in some way. The Colorado
cutting rack is a box on legs with slanted or sloping bot-
tom, having an opening at the side. To the rim of a
ledge at the front of the operator, a knife is fastened
with the point vertical. The seed rolls through the ad-
justable opening at the side to the ledge. The operator
picks up the seed without motion except that of his hand
and wrist and cuts the seed by pulling against the knife.
Some operators prefer to push against the knife, but the
pulling motion is better because the eyes are then always
in view, and better judgment can be used in allotting the
eyes to the different pieces from each potato. The cut
pieces drop into a crate or sack. Trouble with potato
diseases of the seed makes it always advisable to have
some means of disinfecting the cutting knives, even if
the seed is soaked, as no treatment reaches into the in-
terior of the tuber. All seed suspected of being danger-
ously diseased should, of course, be thrown away. A
dish of formaldehyde solution in which to disinfect the
knife is advisable. Corrosive sublimate solution is a
better disinfectant, but is a very dangerous poison to have
around.

With the Colorado cutting rack, the operator can do

Planting 157

even better work than with the knife hekl in the hand
and can cut nearly or twice as fast with less fatigue, due
to the fact that there is no lost motion in reaching some
distance for every potato cut. All roll down to within a
few inches of the hand. The cost is small, being only
that of a little rough lumber, as the knives can be used
for other purposes. A knife may be held by fastening to
a board and potatoes picked from a crate. Any knife
used in cutting seed should be ground thin and kept
very sharp.

Under most conditions a larger yield is secured by
planting as fast as the seed is cut. The reduction of yield
of seed allowed to dry may be heavy. Lack of labor in
planting time often leads farmers to cut seed in periods
of bad weather and to save the time of cutting later. To
prevent the loss of seed by heating, it should be kept in
separated containers, as sacks or crates, with a small
amount in each in a cool place. The moisture on cut sur-
faces must be dry to prevent heating and rot, but no more
drying should be allowed. Such carefully dried cut seed
may do better than freshly cut in cold and wet soil.
Land plaster (gypsum) may be used to dry cut seed.
Sulphur has been advocated for disease-prevention, but
its use does not completely prevent any disease and it
is very disagreeable to handle.

The principles of seed cutting are as follows : —

(1) Seed pieces should be cut blocky in shape to
make surfaces as small as possible. Blocky pieces feed
better through machine planters and the smaller exposed
cut surface reduces loss of moisture and danger of infec-
tion by rot germ (see Plate VIII).

(2) The probability in most cases that the seed and
eyes are more vigorous makes it better to cut each tuber

158 The Potato

in such shaped pieces that will give the largest number
having eyes from the seed end. Seed of size to make two
pieces should be halved through center of seed end group
of eyes. Tubers short and round enough to make four
pieces without their being too long and slender should be
quartered through the seed end group. Those which
will make too slender quarters cut in this way should be
cut once lengthwise and then transversely, making four
blocky pieces. Many tubers will be the right size and
weight to furnish three seed pieces. These should be
cut with one piece taken off the stem end about one-third
of the length from the stem and the remainder of the
tuber halved through the seed end group of eyes. This
gives two out of tliree pieces with a more vigorous seed
end eye and the third being cut with a little more flesh
to make up for the slower start given by its eyes compared
with those of the seed end.

Fairly blocky seed large enough for six pieces is cut in a
similar way, splitting the stem end into two pieces and
the seed end into four. Seed cutting into more than
six pieces often has so few eyes, compared with the amount
of flesh, that it is difficult to cut well, especially towards
the stem end. The seed end of such large seed should
usually be cut into four pieces.

(3) To make sure of one good eye on every seed piece,
it is well to have two wherever possible.

(4) The average weight of the seed must be adjusted
to the needs of the crop for the soil planted. Garden
soils will need little more than the eye itself to produce
plants, while soils in very poor condition need large seed
to furnish nourishment to the young growing plant for
some time before it can grow roots far enough to support
itself. The commonest size of seed used runs from one

Planting 159

to two ounces. The average amount of seed used to the
acre in America is estimated at 11 to 12 bushels, the
range in most cases being from 9 to 16 bushels. Under
European conditions, growers find it profitable to plant
larger amounts. In England a long ton, or about 37
bushels to the acre, is the usual amount and is often
exceeded.

CHAPTER VIII

CARE OF THE GROWING CROP
By Daniel Dean

The tillage of the potato crop is best considered as a
connected whole from the time of plowing until the last
cultiv^ation. The results of tillage before planting and
after, in rendering soil fertility available, in conserving
moisture and in killing weeds are the same. There is no
danger of injury to the growing plant before planting.
Therefore, as large a part of the tillage of the potato as
practicable should be done before planting. If soil
moisture has been well conserved, plant-food made avail-
able and a large part of the weeds in the soil killed, the
amount of the tillage after planting can be largely reduced.
The danger of injury to the plants can thus be largely
prevented. The cost of tillage with wide tools like the
harrows is less than that of work between rows. Only
careful men can be trusted to work tools between rows
without danger, while much poorer labor can work in the
open field. When plowing is delayed until just before
planting, a dry period following will badly injure the crop.

Tillage is most profitable when given at one particular
time. After every rain the soil is at first too wet and stiff
to work without injury. It should be carefully watched
until in the driest part of the field it becomes mellow
enough to work. At this stage, the soil crumbles easily
160

Care of the Growing Crop 161

and has passed the time at which stirring will cause baking.
Stirring the soil at this time saves the maximum amount
of moisture for the use of the growing crop. Evaporation
is so rapid that a few hours' delay results in a great loss of
water. The air is usually cool and the soil stirs easily.
With fresh horses, a large area can be covered in a few
hours. Weed seeds which have been sprouted by the re-
cent rains are stirred about and the weeds killed. Grow-
ing weeds which have escaped previous cultivation are
torn out and left on top of the soil to be dried and killed
by the heat of the sun. The potato plants have just
received the stimulation of needed rain and the dissolved
plant-food which has been forming in the soil during dry
weather but not available on account of lack of moisture.
Under these conditions, the potatoes can stand root
injury which would be more dangerous at drier times.

Wide tools can be used in tillage nearly up to the time
the sprouts break through the surface of the soil. The
common practice in the principal potato-growing states,
outside of Maine, of harrowing down the ridges, left by
the planter or by ridging tools after planting, is very
beneficial. Plank-floats or clod-crushers are often used,
but they are dangerous to the growing sprouts. The
ideal tool for this purpose would be a level which would
smooth down the ridges without crushing the soil around the
sprouts. A tool made of plank 2 X 10 inch standing on
edge and long enough to cover two rows, has been found
very useful. The driver stands on a horizontal plank
fastened to the rear of the plank which does the work.
According to the hardness of the soil, the vertical plank
is slanted slightly or dropped below the level of the hori-
zontal plank. Frequent adjustment is needed as the soil
changes texture rapidly after rains. The horse should be

162 TJie Potato

hitched close to the level to keep it from digging into the
soil. On any but perfectly level fields, the use of level or
harrow on more than two rows at a time is likely to result
either in injury from working one row too deeply or 'in
poor work from going too shallow on one and hurting the
others. Leveling the rows can be delayed longer when the
seed is covered deeply. Many stones in the soil make it
advisable to level earlier if it can be done at all on account
of stones moving the seed.

A practice used much in IVIaine and suited to wet and
cold climates is to ridge the potato rows just after the
plants come up. If frost follows, the plants are safe from
it for several days longer than if left uncovered. Such
ridging kills many weeds, but is suited only to sections in
which the soil is sure not to bake over the little plants, and
to conditions of damp soil which make ridging the best
practice.

Without heavy ridging late in the season, the weeds
hardest to control are those closest to the potato plants.
Thorough stirring before the plants come up and a fre-
quent use of the weeder afterwards enables one to control
the weeds near the plants as easily as those between the
rows.

Many forms of cultivators are made for tilling the soil
between the rows of potatoes. Very heavy soils, such as
those of the Greeley region of Colorado, need four-horse
cultivators which use two teeth four inches wide and four-
teen inches long on each side of the row and stir the heavy
clay to the depth of eight or ten inches. Other cultivators
for light sandy soils may merely stir the surface with twelve
or fourteen peg teeth. Between these types, every grada-
tion of size and number of teeth may be found according to
the soil conditions.

Care of the Growing Crop 163

As a general rule the first cultivation after planting is
made as deep and as close to the seed as possible, because
the potato roots have not started far yet and are safe from
injury. The soil settles together so quickly that it should
be kept mellow in this way as long as possible. Sometimes
a second deep cultivation may be given. Later cultiva-
tions after the roots start are made with the teeth working as
shallow as they can be made to work, so as to form a mellow
soil mulch. This depth will vary in different soils from one
to three inches. ]\Ieasurement will show that cultivator
teeth often work much deeper than the grower is aware.
As the tops begin to grow and form a mass, the cultivator
teeth can be narrowed. Weeds start less in the shade of
the tops and evaporation becomes less, partly on account
of the shade and partly because surface roots form to use
the moisture. Wide, deep teeth are manufactured to
cut the roots of perennial weeds like the Canada thistle.
Such teeth may often be substituted in part for the com-
mon teeth. Cultivators are made for one, two, three or
four horses, with wdieels and without, and for the driver
to walk or ride. One-horse walking cultivators, common
in the East and South, have great disadvantages. Even
when fitted with wheels in front to regulate the depth, the
teeth cut much deeper in some soils than in others. The
machine is too light to hold in the soil in stony ground.
Masses of weed roots, like those of quack- or witch-grass,
clog the teeth and cause the teeth to rise out of the soil at
the very places where the best work is needed. Wheel
cultivators enable one to regulate the depth of working to
better advantage. The weight of the wheel cultivators,
with that of the driver, holds the teeth into the ground
among stones and weeds. The wheels prevent the teeth
from cutting too deeply in mellow places free from weeds.

164 The Potato

Deep cultivation is most dangerous in dry times. The
gain from weed killing may be offset by the loss of the
potato roots.

A tool which is used less than it should be is the weeder.
Weeds like ragweed, foxtail or barn grass, pigweed and
the whole class which grow from small seeds in the potato
field are very easily killed by the frequent use of the weeder
until the potatoes are nearly a foot high. Weeders are
made with either two or three rows of teeth, with wheels
and without and Avith different styles of teeth. The prin-
ciple is the same in all, that the light and somewhat flexible
teeth tear out and destroy the tiny weeds starting in the
surface soil with little or no injury to the larger sized potato
vines. The weeder is a tool which demands certain soil
conditions to be effective. It will not work at all on hard
soil. Many growers have discarded weeders after trying
them where the soil was not suited to their use. Most
soils have a short period after every rain when the flexible
weeder teeth are able to penetrate and stir the soil. If
that time is taken for their use, many sprouting weeds
can be killed in a very short time and the surface mulch
established close to the potato plant. The weight of the
weeder selected and the stiffness of the teeth should be
carefully chosen according to the character of the soil. If
necessary, weight can be added. A needed precaution in
the use of the weeder is to keep the teeth free from trash.
Weeders are often used to follow a cultivator with large
teeth to better level the soil between the rows. Weeders
and leveling tools, like the harrow, are sometimes driven
crossways of the potato row. It may be possible to do
the work a little better in this way, but the danger of injury
to the growing sprouts and roots of the potatoes from
crushing under the feet of the horses is so great that it is a

Care of the Growing Crop 165

practice of doubtful advantage. In most cases, practically
all of the weeds can be killed by driving along the row.
The weeder is a tool for prevention of weeds rather than
their cure. It will not kill those which have got much of a
start above the soil or those with underground rootstocks
like quack-grass.

A comparison of potato-growing of 1916 with that of 50 to
75 years ago shows how great has been the substitution of
tools operated by the power of animals for those worked by
man. Where formerly the plow and harrow were nearly
the only tools not worked by hand labor, the farmer may
now use the horse-drawn planter, fertilizer-sower, manure-
spreader, numerous types of cultivators, weeders, ridgers
and other tillage tools, the sprayer and the different types
of diggers.

Within the last twenty years the gasoline engine has
been developed to a wonderful degree. Millions have been
built for automobiles and probably millions more have
been sold for farm use, for threshing, feed grinding, pump-
ing water and other uses. Gasoline tractors are being
rapidly developed to draw farm tools in the field. As yet
they have been little used in potato-growing except for
plowing and harrowing. A great obstacle to the use of
present tractors between potato rows is the width of a track,
usually four or five feet. Potato rows are usually about
three feet apart and tools for work between the rows must
have a tread of about three feet, or else have a six-foot
tread, like most potato sprayers. Four-wheeled tractors
used to draw tools need two operators, one for the tractor
and another to handle the tools. On any but perfectly
level land the side movements of front or rear wheels in
skidding quickly injure the potato plant. New types of
tractors are being developed by which the same two wheels

166 The Potato

are used for driving and steering, the tool itself taking the
place of the other wheels of the tractor. One operator
handles both engine and tools. Similar small engine-
propelled tools are being made for garden use.

Engines are being used on potato sprayers to give better
results by higher pressures than horses can furnish. The
elevating and separating machinery of potato diggers is
sometimes driven by engines, horses being used to draw
the tool only.

Harrows or leveling tools are usually used once ; occa-
sionally twice. Weeders may be used up to a dozen times
in extreme cases and half a dozen pay well. Cultivators
are used from three to eight times with four or six as
the most common number. Outside of Maine, the ridging
tools are used once or twice. Thorough tillage and a good
condition of the soil before planting necessitate less work
later. It is a good rule to cultivate after every heavy
rain, and to cultivate more frequently in hard soils than in
light. Tillage is less needed in soils which are mellow and
full of organic matter, because such soils supply plant-food
and water more readily.

The danger of the growing tubers protruding out of the
soil and being sunburned is prevented by ridging lightly
after the tubers are formed. Ridging earlier does not pre-
vent sunburn because the depth at which the tubers form is
controlled by the depth of planting. Very shallow plant-
ing results in the tubers forming below the seed and very
deep planting in forming at a depth where little sunburn-
ing results. Usual depths of planting are not deep enough
to entirely prevent sunburn. While late ridging is some-
what feasible, the difficulty is that any injury to the roots
of the growing potato plant at that stage is dangerous.

Tillage is so necessary in potato-growing for the libera-

Care of the Growing Crop 167

tion of plant-food, maintenance of healthful soil conditions,
saving moisture and weed killing that it must be practiced
after planting the potato crop. As the potato plants are
more tender than most weeds, great injury may result from
careless tillage. The tender white sprouts starting from
the seed tubers are usually injured by a touch. The soil
about the seed may be thoroughly stirred with a harrow
and level during the first few days after planting without
danger. The weeder can be used with good results in
killing weeds and keeping a soil mulch above the plants
if great care is used to prevent the teeth from injuring the
sprouts. If the number of injured sprouts is small, the gain
from the tillage may outweigh the setback which the in-
jured plants receive.

The next period, from the time the plants form green
leaves above the ground till the tops are eight to twelve
inches high, is one when the benefits of tillage are usually
greater than possible injury. During a large part of the
time the plant-food in the seed tubers is still available, and
the leaf surface is not yet large enough to transpire enough
water to seriously injure the plant. Sun-scald and tip-
burn are not common imtil the plants are larger. Roots
are being developed close around the seed and stalks.
Until the roots are numerous enough for tillage to destroy
more than a small proportion of the whole root system,
tillage is beneficial. Later the horizontal roots extend
until they cross between the rows. These roots are now of
the size to make their injury a serious matter to the grow-
ing plant. The greatest development of the roots is in
the plowed area, or five to ten inches below the surface.
Many roots also extend down to the depth of three to four
feet. A large part of these vertical roots drop downward
from the large horizontal roots close to the surface. It is

168 The Potato

very difficult to use any cultivator or ridging tool late in
the season without cutting these lateral roots. The loss
of root area is further increased by the loss of the vertical
roots attached to these lateral ones.

The relation of the value of these roots to the yield of
the crop is vital. One function of the roots of the growing
plants is to take in water containing plant-food in solution.
The water is transpired from the lea\es and the plant-
food transformed into material for further growth of the
plant. Transpiration from the leaves of the potato is less
easily checked in periods of drought than with many other
plants. The potato has less ability to regulate its use of
w^ater by the supply available. Removing part of the
leaves by pruning or by attacks of disease reduces the yield
by taking away from the plant the factory in which the
material for the tubers is elaborated. As the supply of
water and plant-food remains the same, such pruning may
even be of benefit in the cases where the normal food
supply is deficient. The removal of part of the roots not
only removes a fraction of the supply of water and food,
but, from the nature of the plant, throws it out of balance.
The leaves continue to transpire water, and in the lack of
full supply from the root, use up part of the water in the
plant itself. The whole plant suffers, the greatest injury
showing at the tips of the leaves. The ends of the leaves
dry up and die, a trouble commonly called "tip-burn."

The strain upon the potato from exhausting effects of
blossoming and forming tubers at nearly the same time is
very heavy. The heat and drought which often occur at
this time add to the troubles of the plants. Any damage
to the plant is now more dangerous than before. At this
time, tillage may be beneficial or may be very injurious.
If the weather is cool and the soil water ample, tillage may

Care of the Growing Crop 169

gret.tly increase the crop. Hot and dry weather, at or
following the time of tillage, may nearly ruin the crop,
weakened by root injury.

Tillage so loosens the upper inches of the soil that the
roots cannot de\'elop there until after tillage stops. The
plant-food contained therein may be of great value to the
growing crop. Exhaustive experiments show that with
corn practically the same amount of water is found in the
soil late in the season whether tilled or not. The plant
roots are able to use the water before it can escape from the
surface.^ If weeds have been killed, there is little need of
stirring the soil late in the season. The frequent grinding
of the upper soil layer by early tillage has changed much
of its contained plant-food into a condition in which it is
available to the plants. If the previous care has been such
that the crop has passed the critical period in good condi-
tion, the roots soon fill the surface soil and use the plant-
food supply for the production of tubers. A few weeds
which may have escaped the tillage tools should be pulled
by hand in July and August before they go to seed.

Spraying is commonly thought of only in its relation to
insects and diseases. Thorough spraying with bordeaux
has been found to give an increase in yield in the absence
of disease and insects. This action is noted most in hot
and dry seasons. It should always be considered among
the methods to insure good yields in sections where heat
and drought are likely to limit the yield.

1 111. Bui. 181. Bui. 257, Bur. PI. Ind., U. S. Dept. Agr.

CHAPTER IX

POTATO INSECTS AND THEIR CONTROL

The amount of damage to the potato crop by insects
is very large, much larger than is ordinarily supposed.
Spraying with poisonous substances has to be resorted to
in order to obtain a crop which has been uninjured by
insects. They do four kinds of damage and may be clas-
sified in this manner: (1) insects chewing the leaves;
(2) insects sucking the leaves and tips ; (3) stalk borers ;
and (4) insects affecting the tubers. Most of the damage
is done by the Colorado potato-beetle and the flea-beetle.

The Colorado jJotato-beeUe {Leptinotarsa decemlineata)
(Fig. 10).

This is a leaf-eating insect, and its ravages are very
general. It seems to be always present where potatoes
are grown, and the damage it causes is very great. Indeed,
in most sections, it is impossible to obtain a crop at all
unless its ravages are held in check by the application of
some poisonous substance to the leaves.

This insect is a native of a strip of country which lies
just east of the Rocky Mountain range and includes eastern
Colorado. In its native state the beetle lives upon the
wild weeds of the potato family, the chief of which is the
sandbur (*S. rostratum). It is a general feeder, living on
170

Potato Insects and their Control 171

not only potatoes, but tomatoes, eggplants, tobacco and
peppers.

"It was first brought to notice," says Geo, C. Butz,
"about the year 1856. In 1861 it was found in the potato
fields of the settlers of Kansas. In 1862 it was in Iowa, and
in 1862 it appeared in southwestern Wisconsin. It crossed
the Mississippi River into Illinois in 1864. It was in
Michigan and Indiana in 1867, Ohio in 1868 and Pennsyl-
vania in 1870. It moved eastward at the rate of about fifty
miles a year for a number of years, but later it traveled
more rapidly. It is reported to have reached the Atlantic
Coast about 1874, and Nova Scotia about 1882. When it
reached the Atlantic Coast, it had traveled 1500 miles in
sixteen years, and nearly 1000 miles more the next eight
years in its march to Nova Scotia."

The mature beetle hibernates in winter in the ground
usually at a depth of eight to ten inches and begins to fly
early in the spring. As soon as the first leaves of the po-
tato appear above the ground, the beetles fly to them and
soon lay their reddish yellow or orange-colored eggs in
clusters on the under side of the leaves. In about a
week the young beetles or larvae appear and begin to
devour the foliage with great rapidity. The larvae
pass through four stages or instars and are mature in
sixteen to twenty-one days, according to the weather.
Then they go into the ground and transform into the pupa
or resting stage, in which they remain at least a week —
usually longer — before coming out as the adult beetles.
The egg-laying period lasts about thirty-five or forty days.
The minimum time for the life cycle is about four weeks.
The last brood of larvae which disappear into the soil
before severe frost pupate there, remaining in the ground
in the form of perfect insects until the following spring.

172 The Potato

The adult beetle is oval in shape, about three-eighths of
an inch in length and a trifle narrower than long. The
ground is yellow and the wings are marked by ten black
lines running lengthwise. There are also black markings
on the thorax (see Fig. 10). These insects have great
power of endurance. They will walk for great distances in
search of food, and it is said by direct experiment they are
known to have lived thirty days without food. Their
eggs are a bright yellow when fresh and the young are
dark red or brown grubs with black heads and markings
of black spots in double rows
on each side. The color be-
comes lighter as the grubs
mature.

Control. — The Colorado
potato-beetle is controlled by
the use of poisonous sub-
* ^ stances which either in solu-

FiG. 10. Potato bug, larva and ,• • i

mature beetle enlarged. tion or suspension are sprayed

upon the vines. The most
common of these arsenical poisons are paris green, arsenate
of lead or arsenate of soda. Any one of them may be
sprayed upon the vines alone or mixed with bordeaux mix-
ture and applied. Poison is usually necessary only for the
first two regular sprayings, but should be added at any time
the larvae become numerous. The eggs should be watched
carefully, and after they are well hatched and the young
have begun to feed, the first application of the poison
should be made. A second spraying will doubtless be
necessary in ten days to two weeks. The necessity for
subsequent applications of poison will be determined by
any later appearance of the pests. The first sprayings
should not be delayed too long, as the larvae develop very

Potato Insects and their Control 173

rapidly after hatching and much harm is often done before
one is aware of it. With fifty gallons of water, if the poison
is to be used alone, or of bordeaux mixture, use three to
five pounds of arsenate of lead or one pound of paris green,
and add two pounds of quicklime to prevent burning.
One pound of paris green to the acre in either water or
bordeaux mixture is ordinarily recommended. Growers
should be warned against the use of excessive quantities of
paris green because it burns and injures the vines if put on
too strong. Arsenate of lead has the advantage of adher-
ing to the vines and is only slightly washed off by rains.
After long-continued rains, the vines may often be seen
to be grayish in color because of the arsenate still clinging
to them. When these poisons are applied with water,
whether with or without bordeaux mixture, some provision
must be made to keep them constantly agitated so that
they will not settle to the bottom of the spray tank.

Flea-beetle {Epitrix cucumeris) (Fig. 11)

This is a leaf-eating insect. There are several kinds of
flea-beetles which are troublesome to potatoes, the one
named above being the most common. In the South the
tobacco flea-beetle {Epitrix parvula) and the eggplant
flea-beetle {Epitrix fuscnla) do considerable damage.
Another larger, more elongated form, known as Systena
hudsonias, has been found to cause considerable damage
in the North.

These flea-beetles all belong to the leaf-chewing class.
The adult beetles frequently do much damage to the
potato crop, but being so small, less than one-twentieth
of an inch, they are often not seen. They are black and
jump when alarmed, which also makes it difficult to see

174 The Potato

them. The result of their depredations will be found in
the many small holes which may be noticed in the leaves
of the young potato plants, and in the lessening of the
crop on this account. These many small holes make
excellent starting places for many diseases to get a foot-
hold to injure the plant. The beetles stay mostly on the
under side of the leaves and are not seen, their presence
being detected only by their work. The larvae occasion-
ally do injury by mining into the
tubers and cause pimply potatoes.
During the hot, dry summers,
especially, they often become the
worst enemies of the potato. The
insects very often congregate in
b such numbers that the leaves of the

Fig. 11. Flea-beetle, plants appear almost black with
them. Young potatoes and newly
set tomato plants frequently have their leaves so badly
eaten that they shrivel, and the tomatoes may die.

The life histories of the different flea-beetles are prac-
tically the same. The adult insects live over winter under
leaves and rubbish and appear during the latter part of
May and first of June. As soon as they come out, they
lay eggs near the roots of the potatoes or of weeds related
to them. The larvae mine into the roots ; and when full
grown, they pupate and later emerge as adult flea-beetles.
In some sections, particularly in Colorado, the greatest
damage is done by the larvse, which are tiny white grubs
about a quarter of an inch in length. They frequently cut
into and destroy the young tuber stems of the potato and
prevent a regular setting of the crop.

One brood of potato flea-beetle appears yearly in the
North and two broods in the South, the second ordinarily

Potato Insects and their Control 175

appearing in August and September. This brood, coming
at a time when the tubers are partially or wholly grown,
bores into the flesh and underneath the skin of the potato,
causing a pimply or scabby appearance which detracts
from their market value.

Control. — Flea-beetles are very largely controlled by
bordeaux mixture, which acts as an effective repellant.
They ordinarily feed, however, on the under side of the
leaves, and thorough spraying both on the upper and lower
sides of the leaf is necessary to be satisfactorily effective.
Spraying may have to be begun somewhat earlier for the
flea-beetle than for other insects or diseases. The insects
are so small and their damage begins on the under side of the
leaves, so that often a great amount of damage may have
been done before it is detected. It is a good practice to
eliminate from the farm such plants of the solanacese fam-
ily as nightshade, bitter-sweet, horse-nettles, ground cherry
and jimson weed. The flea-beetles breed on these as well
as the potato itself.

Blister-beetle {Epicauta and Macrobasis)

These are leaf-eating insects. The so-called "blister-
beetle" or "old-fashioned potato-bug" consists of four or
five species of insects which do a tremendous amount of
damage to the potato in some years. They sometimes
appear in great numbers and are not easily vanquished.
They are all medium-sized elongated beetles of different
colors : spotted, striped, black, light or dark gray. The
adults damage the potato plant, but the larvae are especially
beneficial in destroying the egg masses of the grasshoppers.

A large number of eggs are deposited by the female in a
small cavity in the ground. The larvae are provided with

176 The Potato

legs by which they crawl about until they find a grass-
hopper's egg mass, upon which they feed. They then molt,
their legs becoming rudimentary. As helpless grubs they
complete the remainder of their larval stage surrounded
by an abundance of food. There is one brood a year.

Control. — If potatoes are carefully sprayed for the
Colorado potato-beetle and flea-beetle, there will be little
danger from the attack of these insects. Sometimes,
however, they appear in large numbers and should be im-
mediately killed by additional applications of arsenical
poisons.

The three-lined leaf-beetle {Lema trilineata)

These leaf-beetles are leaf-eating insects. Both the
adults and larvse of this insect feed on potato leaves. This
beetle is smaller and more elongated than the Colorado
potato beetle and has only three black lines on a yellow
ground color. The larvae are distinguished by having their
backs covered with their own excrement.

The adults hibernate over winter and come out in the
spring, laying their eggs on the underside of the potato
leaves along the veins. There are two broods a year ; the
larvse of the first brood appear in June and those of the
second brood in August. The adults of the second brood
go into the ground to hibernate over winter.

Control. — This insect is controlled in exactly the same
way as the blister beetles.

Tortoise-beetles (Cassida and Coptocycla)

Tortoise-beetles are leaf-eating insects. The insects
of these genera are of minor importance, but may do some
damage in unsprayed fields. Their oval shape and flaring

Potato Insects and their Control 177

edge of the thorax give them some resemblance to a
tortoise shell. They are of small size and green, gold or
black in color.

The adults make their appearance in May, having lived
through the winter in crevices under bark and in similar
dry places wherever shelter could be found. The female
begins to lay eggs soon after her appearance. The eggs
are laid singly on the leaf-stems or on the under side along
the larger veins, and each is covered with a little daub of
black excrement, so that all that is visible to the eye is a
little mass of black, pasty material that soon hardens.
This mass incloses the whitish oval egg and protects it.
During the first part of June, many of the eggs have
hatched and larvse, eggs and adults may be found on the
plants all at once. "The larvae are decidedly flattened,
more or less oval, with lateral spines or processes from the
margins, and at the end of the body is a fork which, in
some species, holds all the excrement voided during life
and sometimes the cast skins as well, often making a mass
nearly as large as the larvae itself." These feed, pref-
erably, on the under surface of the leaves and do much
damage. The larva pupates about the middle of July.
The beetles appear during early August and feed very little,
all trace being gone before the beginning of September.
There is one brood a year.

The potato jAant-louse (Macrosiphum solanifolu)

This plant-louse is relatively large in size, and either pink
or green in color. Its mouth-parts, like those of all plant-
lice, are adapted for sucking the juices from the tender,
growing tips of the vines. The infested vines grow brown
at the ends and often die back for four or five inches. In

178 The Potato

certain seasons, these insects become very numerous and
their depredations check the growth of the vines con-
siderably. The wounds made by the beaks of the aphids
often admit fungi and indirectly result in greater injury
than the work of the insect alone.

The potato aphid passes the winter in the egg stage,
the eggs being attached to weeds. In the early spring, the
adult insects are to be found feeding on the succulent tips
of rose bushes. In July, the aphids migrate to potato
fields and start feeding there. The potato seems to be an
ideal food for this insect, for it increases in numbers very
rapidly, a single female often producing over fifty young
in two weeks. Late in August or early in September,
the lice leave the potato vines and go to rose bushes or
other food plants. Here they produce several more
generations of young. The last generation of the year
consists of wingless females and winged males. The
females lay the over-wintering eggs on the shepherd's
purse, potato, and other food plants.

Control. — There are certain natural agencies of control
over these insects which frequently make them of little
consequence. Among these are cold weather, frequent
rains, parasitic fungi and insects, and various predacious
insects. These factors cannot be relied upon, however,
to keep the pest in check every year. Fall plowing will
turn under many weeds and old leaves on which the eggs
have been laid. It has also been suggested that the
farmer burn the dead vines in the fall in order to destroy
the eggs. The adult insects can be killed by using any
good contact insecticide like one of the tobacco extracts,
kerosene emulsion and the like. Spraying is usually only
resorted to when the insects become very troublesome.

Potato Insects and their Control 179

Leaf-hoppers (Empoasca mail)

These leaf-sucking insects do some damage to potato
tops by sucking the juices and making holes in the leaves.
The most common of the leaf-hoppers is Empoasca rnali,
which is a small, elongated, pale-green insect, very active,
jumping and fl^'ing readily.

This insect spends the winter either in the adult or in
the egg stage. It appears in the spring and starts to feed
upon the apple or other food plants, and soon lays its eggs.
The nymphs from the over-wintering eggs are found about
the middle of May. Usually about four broods develop
during the season. The leaf-hoppers are generally all gone
by the first of October.

Control. — They do not require special treatment, never
appearing in sufficient numbers to do any great damage.
Treatment for other insects readily keeps them in check.

The potato-stalk weevil {Trichobaris trinotata)

This is a stalk-boring insect which does considerable
damage in the south central states. The adults are small
ash-gray beetles with a long snout, and the larvae are small
white grubs.

The adults appear in the spring after hibernation and
eat holes in the base of the stalk with their long snouts and
deposit an egg in each hole. These soon hatch, and the
larvae make their way into the main stalk and branches.
These grubs become full grown near the middle of August,
and then they pupate in cocoons which they have spun
near the base of the stalks. Adults appear a w^eek later
and remain in the stalks until the following year.

Control. — Since the adults hibernate in the old stalks,

180 The Potato

the best method to keep them in check is to rake the fields
over after digging the potatoes and burn all the refuse.
Destroy also all other solanaceous plants which may be
growing in the neighborhood.

The stalk-borer (Papaipema nitella)

The potato is probably not the normal food plant of this
insect, but when other food material, such as certain weeds,
tomatoes, corn, cotton and some grasses, are lacking, the
potato is sometimes infested. The adult is a gray moth,
and the larvae do damage by boring into the stems of the
plants on which they feed.

The insect lives over winter by means of eggs which are
laid in the fall in masses of fifty or sixty on grasses and
weeds. The eggs hatch in the spring, and the larvae
puncture the leaves and then work down into the stalk.
Frequently they travel from one plant to another. The
larvae, when mature, eat holes in the sides of the stalks and
pupate. Late in August, the adults emerge and lay eggs
for next year's flock. There is one generation in a year.

Control. — The stalk-borer should have the same treat-
ment as the stalk-weevil.

White grubs (Lachnosterna species) (Fig. 12)

These are the larvae of the May-beetles or June-bugs.
They are large, white, soft-bodied grubs which are com-
monly found in sod ground. They feed on the roots of
many plants and sometimes eat into the tubers of pota-
toes, especially those planted on new ground.

This insect lives in the ground over winter either as an

Potato Insects and their Control

181

adult beetle or as white grubs. It takes two or three
years to complete its life cycle. The adults lay eggs in
sod ground in June which hatch in about two weeks. The
larvae or grubs feed on roots and require one or two sum-
mers to become fully grown.
They pass the first winter as
grubs living deep down in the
ground and the second summer
are much larger and more
destructive than the first, so
that those fields left in sod one
year are likely to be badly in-
fested the next year. The
larva, ordinarily, pupates in
June or July of its second year
and after remaining a pupa for about three weeks, changes
into an adult beetle and remains in the ground until the
next spring.

Control. — If the ground is badly infested with white
grubs or wire-worms, it should be given a thorough fall
plowing and either plowed again or thoroughly harrowed
in the spring. Land which has been in sod for many years
would ordinarily need this treatment. Potatoes should
not be planted immediately upon such ground, but it
should be planted for a year or two to such crops as buck-
wheat or some of the other small grains which are damaged
but little bv white grubs or wire-worms.

Fig. 12. White grub and
May-beetle.

Wire-tcorms (several species) (Fig. 13)

These insects do much damage to the roots of many crops,
including the potato. Like the white grubs, they normally
live in sod ground and feed on roots, and are not usually

182

The Potato

injurious to potatoes unless the ground has been in sod a
year or two. Wire-worms are the
long, hard, cylindrical larvse of the
click beetles. They include several
species.

Like the June-bugs, the eggs are
laid on sod ground and the larvae
require from three to five years to
mature. They transform to adults
under ground in midsummer, but
usually remain in the soil until the
following spring.
See methods of control of white grubs.

Fig. 13. Wire-worm
and the beetle.

Control.

CHAPTER X

DISEASES OF THE POTATO

By M. F. Barrus

When healthy potatoes are planted in a warm, moist soil,
vigorous sprouts will grow up from the tubers. These
develop into vines with green expanded leaves. On
underground stems there will be formed young tubers
which enlarge greatly in the latter period of the growth
of the plant. When the healthy tuber is planted, the
food stored within is used for the production of tissue
for roots, stems and leaves. As soon as the leaves have
expanded they perform the important task of making
food during daylight from the carbon dioxide of the air
and from water and soil solutions absorbed by the roots.
This food is used for the maintenance and further growth
of the plants, and whatever is made in excess of this is
stored in the tuber largely in the form of starch. After
the vines have obtained their greatest growth, the leaves
make a large excess of food above that needed for main-
tenance, and consequently the storage of food in the tuber
takes place rapidly. It is plainly to be seen, therefore,
that in order to have a large amount of food stored in
the tubers, that is, to have a large yield, it is necessary
first to have a good growth of vines and to have them
remain healthy until the tubers become of maximum size.
A destruction of the leaves by any means reduces the
yield of tubers.

183

184 TJie Potato

Wlien the leaves of the plant become crinkled and
curled, mottled, rolled, spotted, blighted or dead at the
edge, when the vines show a yellowing and wilting, or
become stunted, or the stem shows discolorations on the
outside or within, or when the tubers have rough scabs
or pustules or show rotted areas, or the tissue within is
streaked with brown or is decayed, we say the plant is
diseased. Any one of these appearances, called symp-
toms, may indicate the presence of disease, and its appear-
ance means that the plant is unable to produce its maxi-
mum yield. It is to the interest of the farmer to know
what these diseases are and especially to know how to
prevent them.

A plant, like a person, may be small and also be healthy.
Poor soil often produces small plants, and late planted
tubers may produce vines which may be killed by frost
before they have attained their maximum growth. Such
small plants are not diseased. Other things being equal,
however, small vines will not produce as large yields as
large vines. But plants may be small because they are
affected by some disease, so that it is often difficult to
tell whether small plants growing in a field are affected
by disease or are small for other reasons. Some plants
grow "all to vines," that is, the vines continue to grow
vigorously all the season and by so doing use up a large
amount of the food made by the leaves so that there is
but little left for storage in the tubers. Such plants
usually have small or unmarketable tubers. This condi-
tion may be brought about by too much shade or by a soil
too rich in nitrogen. On the other hand, such a condition
may be the result of a disease known, for the want of a
better name, as "large vines and many small tubers."

A disease of a plant is an abnormal condition which

Diseases of the Potato

185

prevents it from completely carrying on its life processes
and producing its fruit naturally. There are many
agencies capable of bringing about disease of the potato,
some of which are not well understood at present. Disease
may be brought about by conditions of soil and climate
unfavorable to the
plant, by physiologi-
cal disturbances within
the plant, the direct
cause of which is not
clear, and by the
attacks of parasitic or-
ganisms. Troubles re-
sulting from the first-
named condition may
sometimes be reme-
died by selecting vari-
eties or types of plants
better adapted to the
climate in which they
grow, or by adopting
a system of culture that will overcome or obviate the
unfavorable condition. The second group of troubles
are often heritable, and the only means of avoiding them
are through the elimination of tubers from affected
vines for planting purposes. The third type of disease,
and often the most destructive, is caused by parasitic
organisms and may be communicated to healthy plants
by the transfer of the parasite or some special portion of
its body adapted for the purpose.

For convenience in discussing them, we may classify
parasites of the potato into plant and insect parasites.
The plant parasites include fungi, bacteria and slime-

FiG. 14. Section through a part of a dis-
eased potato leaf, showing the spore stalks,
with spores attached, extending down
through the breathing pores of the leaf.

18G

The Potato

J ^p^^c

molds. A fungus is itself a plant, but without leaves or
green color. It is not able to prepare its own food as
higher plants do, but must live upon the product of other
plants. jNIany fungi and bacteria and most slime-molds
are saprophytes, that is, they obtain food from the prod-
ucts of plants or animals that are dead. Others are
parasites — obtaining their food from the products of
living plants by attacking the living tissues, injuring or
killing them and thus causing a diseased condition in the
plant or the death of the entire plant.

A fungus differs from a higher plant in that it does not
have roots, stems or leaves in the sense in which we
generally regard these organs, but in its vegetative stage

it consists of tiny thread-
like tubes or strands
known collectively as
mycelia. The mycelium
penetrates the food ma-
terial and obtains its nu-
trition from it. After a
period of growth the
mycelium produces its
fruiting body which va-
ries greatly in size, shape
and condition in the dif-
ferent fungi. The fruit-
ing body bears the re-
productive bodies known
as spores (Fig. 15), of which enormous numbers are
usually produced. These are disseminated by water, air
or animals, depending on the kind of fungus producing
them. When spores of parasitic fungi fall upon their
host plant, that is, the plant from which they are able

/^-v

(After U. S. Dept. Agr.)

Fig. 16. Below from right to left
are shovm four stages in the formation
of swarm spores. The way in which
the swarm spores germinate is shown
above.

Diseases of the Potato 187

to extract their food, they will germinate under favorable
conditions of temperature and moisture. Indeed most
spores will germinate under favorable conditions without
the presence of the host plant. These conditions vary
with different fungi, but, in general, a fairly warm, moist
condition is favorable for the germi-
nation of most spores. The sprout,
or germ-tube (Fig. 16), produced by
the germinating spore enters the tis-
sue of the host directly through the
wall which it is able to dissolve, .^^^ ,^^:™;--

through wounds or through the ing germ-tube entering

breathing pores. The root-hairs of ^^ '
higher plants have very tender walls, and these may serve
as a point of infection by parasitic fungi of the soil. After
a fungus gains entrance to a plant, it lives upon the cell
products and usually brings about the death and discol-
oration of the tissues at the point, so that the infested
area may be seen as a spot, rot, blight or canker. The
fungus, sooner or later, puts forth fruiting bodies on the
outside of its host, and on these bodies the spores are
borne.

Bacteria are plants of a lower order than fungi, many
kinds consisting of but a single minute cell. In the
presence of oxygen, water, food and suitable temperature
they reproduce very rapidly. They do not produce
spores like fungi, and are unable to penetrate unaided
the outer tissues of plants, but may enter the plant
through insect and other wounds or through other open-
ings. Thus, parasitic bacteria may be carried from plant
to plant by insects and be introduced into their tissues
during dry weather when fungi would be unable to do
so. Bacteria also live entirely within the host plant and

188

The Potato

do not produce fruiting bodies on the exterior, though
the Hving bacteria may ooze out with the sap through
wounds or breathing pores.

Most shme-molds are entirely saprophytic, though a
few attack hving pLants. The one pro(hicing powdery
scab is the only example of a slime-mold disease of the
potato. The slime-mold differs from a fungus or a bac-
terium in that it consists of a naked mass of protoplasm,
often of many cells, in its vegetative stage. The spores
of the one producing powdery scab germinate as a tiny
mass of naked protoplasm which gains entrance to its
host through the lenticles or breathing pores on the tuber.
It passes from cell to cell within its host, infesting the
contents and itself greatly increasing in mass. Finally,
its body is transformed into spores which become exposed
with the rupture of the skin above them.

CLASSIFICATION OF CAUSES OF DISEASE

According to their causes, we may classify the diseases
of potatoes as follows :

Fungous — Early blight, late blight, and rot,
Fusarium dry rot, Fusarium
wilt, Verticillium wilt, rhi-
zoctoniose, wart, and silver
scurf.

Bacterial — Common scab, black leg, soft
rots, bacterial wilt, streak.

Slime-mold — Powdery scab.
Non- J Curly dwarf, leaf-roll, mosaic, spindling sprout,
parasitic | net necrosis, tip-burn, arsenical injury.

Parasitic •

Diseases of the Potato 189

Early blight (Plate X)

Early blight, caused by the fungus Alternaria solani,
appears as angular, dark brown dead spots on the leaves,
which may become so numerous as to kill the entire leaf.
The spots are marked with concentric rings of elevation,
giving the dead area a target-board appearance. The
vines usually do not become aflFected until after blossom-
ing has occurred, but may then become so severe as to
cause the vines to die. The spots often occur around a
flea-beetle puncture or other injury, but may also be
found on an otherwise uninjured surface. The fungus
commonly attacks the older and weaker leaves first, but
may spread from them to the younger ones.

The disease may be confused with tip-burn or with
arsenical or other injury to the foliage. The fungus
may attack such injured or dead area first and later
spread to healthy tissue. The spores are large, thick-
walled, many-celled bodies produced on both surfaces of
the older dead areas. The fungus is able to live over
winter as a mycelium in the dead leaf tissue, and the spores
themselves will remain alive for more than a year. They
germinate in water, each cell being capable of sending
out a germ-tube. These are able to enter the leaf through
stomates or penetrate the epidermis directly. The
fungus attacks the foliage only, but as a result of the
attack the tubers may be small and thus the loss will be
considerable. This will depend upon the virulence of
the attack and may amount to one-half or more of the
crop.

The disease can be held in check by thorough appli-
cations of bordeaux mixture.

190 The Potato

Late hUght (Plate IX)

Late blight, also known as downy mildew, is caused
by the fungus Phytophthora infestans. It occurs in north-
eastern United States and adjacent parts of Canada and
sporadically farther south and on the Pacific Coast. It
has also been known for years in many countries of Europe,
and has been reported as occurring in Australia and in
the high plateaus of South America where potatoes are
grown. It prevails in those regions where the weather is
relatively cool and moist, conditions most favorable for
the growth of the potato itself, and, even there, is de-
structive only during especially favorable seasons. For
this reason the disease appears in epidemic form in
many sections in occasional periods of years, the inter-
vening periods being comparati^'ely free from it.

The disease shows on the leaves as water-soaked or
brown areas that may occur on any part of the leaf. In
moist weather these spots rapidly enlarge so that the
entire leaf may become affected, and over the recently
affected area, usually on the lower surface, a fine white
mildewy growth may be noticed. The stem may be-
come affected in a similar manner. In moist weather
the affected areas soften instead of drying and give off a
disagreeable odor characteristic of decaying vines.

The fungus causing the late blight may attack the
tubers (Plate IX), the upper surface of those lying nearest
the surface of the soil being first infected, producing on
them a discolored, water-soaked area which may be small
or, if the soil is moist, may extend over much of the tuber.
The affected area becomes somewhat sunken at digging
time or later in storage and the flesh has a rusty-brown
color. This condition is known as dry rot. The flesh

Diseases of the Potato 191

is not affected to a greater depth than one-fourth to one-
half an inch, although such affected tubers in a heavy
wet soil or even in storage may be invaded by saprophytic
fungi or bacteria that produce a soft, malodorous condi-
tion known as wet rot.

The fungus causing late blight lives as a mycelium in or
near the margin of the diseased area in affected tubers.
Wlien such tubers are planted under conditions favorable
to the fungus, namely, a warm moist soil, the mycelium
will grow into shoots often weakening them and some-
times destroying them.

When these affected sprouts succeed in growing, they
appear above the ground as a slender, weak stalk often
hidden by healthy neighboring ones from the same tuber.
On these weak stalks the fungus, during moist weather,
forms its fruiting bodies on which are produced a large
number of spores. These are blown by air currents to
neighboring healthy vines, where, if the vines are wet,
they germinate in two to four hours in an interesting
manner. An opening appears at the tip of the spore,
and six or more zoospores are pushed out as naked masses
of protoplasm that are able to move about in the water
on the leaf surface by means of whip-like strands of
protoplasm extending from their bodies. After moving
about for an hour or so, they settle down on to the sur-
face of the leaf and after a time send out a little tube, the
germ-tube. The germ-tube is able, after a few hours, to
penetrate the surface of the leaf. Once inside, the germ-
tube grows rapidly into a mycelium extending between
the cells and even penetrating them. These cells be-
come disorganized and turn brown and from them the
mycelium obtains its nourishment. Cell after cell is
killed in this manner, and the discoloration resulting upon

192 The Potato

their death is noticed as a blighting of the leaf. After
four or more days, the mycelium has produced fruiting
bodies bearing more spores. These are carried by air
currents or by other means to healthy leaves, which in
turn become infected if the weather is wet, or they fall
to the ground, where during rains they are washed into
the soil. Thus under favorable weather conditions the
fungus may spread from an infected vine to neighboring
ones, causing them to blight, and thence to all the vines
in the field until all are blighted. The spores, washed
into the soil, come into contact with the new tubers and
infect them in much the same manner as the leaves were
infected, so that they rot in the manner described earlier.
If the soil remains wet and soggy, as heavy soils often do
during rainy periods of the fall, the fungus grows luxu-
riantly in the tuber and produces fruiting bodies on its
surface. Spores produced there infect other tubers in
the hill and possibly spread to other hills. It has been
shown that the fungus may fruit on the surface of the
tuber in storage and infect mature tubers there, though
this does not often happen. All that is necessary for
infection of the tubers is the presence of spores on their
surface under moist and fairly mild or cool weather.
Infection readily occurs when the blighting vines come
into contact with freshly dug tubers. These points are
of importance, as it teaches us to leave blighting vines
until they are dead and dry before digging unless we can
dispose of the crop at once or unless there is danger of
the tubers rotting badly in wet soil. Tubers infected
shortly before digging time may show no evidencf of it
then, but the dry rot will appear later in storage.

It has also been shown that throwing the soil over the
tubers with a shovel plow to the depth of four or five

Diseases of the Potato 193

inches before or at the time the vines begin to blight will
prevent a large amount of tuber infection. This method
of control is a makeshift at best, and the practice in some
localities is known to have reduced the yield. Spraying
the soil with bordeaux mixture will aid in preventing
infection of tubers, but usually is not practical.

As the fungus grows best in the tubers under mild or
moderately cool moist conditions, it naturally follows that
infected tubers will rot but little or not at all when stored
in a dry place and held at a low temperature (40° F. or
below). The application of lime or formaldehyde to the
tubers in storage is of no value in preventing rot.

The disease, then, is caused by a fungus carried to the
field with infected tubers. The fungus spores produced
on infected vines spread readily during moist weather
to the other vines in the field and to neighboring fields,
producing blight whenever infection occurs. Many
spores fall from the vines to the soil below and are washed
to the tubers, which upon infection sooner or later show
the dry rot. When the soil remains wet, such tubers
become invaded by other soil fungi and bacteria which
bring about a soft malodorous rot.

As a result of many experiments it has been found that
spraying the vines with bordeaux mixture is the best
practical way to control the disease. Thorough appli-
cations made frequently during the summer to keep the
new growth covered, especially before rainy periods, and
in the late summer and the early fall, will prevent infec-
tion of the vines. If the vines do not blight, the tubers
will not rot. More complete directions regarding spray-
ing practices will be found under the chapter on Control
Measures.

194 The Potato

Rhkoctoniose (Plates X and XII)

This is a name given to the several symptoms of a
disease caused by the fungus Rhizoctonia, which when
producing its perfect spores is known as Corticum vagum
var. solani. The fungus forms small black irregular
masses often the size of a half-pea or smaller on the sur-
face of the tuber. These resemble httle chunks of muck,
but can be readily detected by washing the tuber, for
they do not wash off as soil does although they can be
easily scraped off. These bodies, called sclerotia, enable
the fungus to pass the winter without injury. In the
spring, when planted with the tuber or even when kept
in a moist place, a fine mycelium grows out from them.
This attacks the sprouts and produces cankers on them,
so that the portion above is commonly destroyed.
Younger sprouts may then appear from below the can-
kered area, but these in turn may be infected, so that the
plants are late in making their appearance above the
ground or do not appear at all. Affected plants that
succeed in appearing may continue to grow and produce
well. The fungus, however, commonly attacks and
destroys the stolons and in this way reduces the yield.
Older plants are sometimes weakened by cankers on the
stems, and brown strands of mycelium may be observed
over such affected areas. The cankers may be so severe
that the vines become yellow in color and the leaves roll
upward the same as when the vine is affected with black-
leg. Indeed, in such cases the stem is sometimes found
to be decayed by a black-rot similar to black-leg. Af-
fected vines often have small aerial tubers formed in the
axils of the leaves and the stems themselves are thick-
ened. Such vines usually have a large number of small

■ /"''.S^-.--

j';^>>'

i

I^'^^^hs^ ^ ^ ' •

4

^m^SSty ^

:^k

^flp'

^

^

Plate X. — Potato diseases. Top, part of a potato leaf showing spota

of early blight ; magnified. Bottom, rhizoctoniose.

(Courtesy Dept. of Plant Pathology, College of Agriculture, Cornell University.)

Diseases of the Potato 195

tubers clustered close to the base. The fungus produces
its spores during moist weather on a thin, white, frost-like
growth extending over the base of the stalks.

This fungus is able to attack many kinds of plants and
to live as a saprophyte in the soil from year to year. For
this reason it is difficult, if not impossible, to eradicate it.

The sclerotia on the tubers can be killed by soaking
the tubers in corrosive sublimate solution, and if this
treatment is coupled with a judicious rotation of crops
on the land, the injury from the disease will be greatly
reduced.

Fusarium wilt

This disease is caused by the fungus Fusarium oxy-
sporum, which gains entrance through the roots from in-
fected tubers or from the soil and works upward in sap
vessels, interfering in that way with the normal circulation
of the sap. The fungus mycelium destroys the roots and,
later, fruits on them, producing abundant spores. The
diseased condition of its roots and of the sap vessel causes
a yellowing, dwarfing and finalh- a wilting and dying of
the vines. The stem pulls up easily and its tissues beneath
the outer layer have a light brownish color. This color
in the vascular tissues extends to the roots, stolon, and
tubers. A section across an affected tuber near the stem
end shows a brown ring of sap vessels. This browning of
the vascular ring is associated with some other diseases
and is always found in tubers in which this Fusarium has
developed to any extent, although in the earlier stages of
infection no discoloration may be noticed.

Such diseased tubers should never be used for seed
purposes, as vines coming from them nearly always be-
come infected. The only successful way to control the

196 The Potato

disease is the selection of tubers from healthy plants and
a wide rotation of crops as outlined under the chapter on
Control Measures.

Vertidllium wilt

This wilt is caused by the fungus Verticillium albo-atrum
and shows symptoms much like the Fusarium wilt, and
the two are very easily confused in the field. The fungus
Verticillium gains entrance to the plant in much the same
way and also inhabits the sap vessels of the plant. Af-
fected plants show yellowing, wilting and dying of the
leaves, beginning with the lower ones and progressing
rapidly upward. The plants have a straggling appear-
ance, usually die earlier than is normal and yield poorly.
As with Fusarium wilt the tissues underlying the outer
layers of cells show a brown discoloration, which in this
case extends upwards into the branches as well as down-
ward into the roots, stolons and tubers. The tubers
show a blackened ring in a section of the stem end. The
fungus passes the winter in such infected areas of the
tuber and is also capable of living in the soil. The same
methods of control should be practiced as for Fusarium
wilt.

Fusarium dry rot (Plate XI)

This rot, caused by one or more species of Fusaria, is
a dry rot extending deep into the tuber. The surface
of the rotted area is much wrinkled and often shows
numerous clusters of a white, moldy growth. The fun-
gus gains entrance to the tuber through the skin wounds
or through lesions caused by other fungi, so that the rot
may occur at any point on the tuber. The powdery
dry rot caused by Fusarium trichothecioides, common in

Diseases of the Potato 197

the western United States, "spreads rapidly in potatoes
in transit to market or stored under unfavorable condi-
tions." None of these dry rots is known to affect the vine
to any extent. The fungi causing them will live in the
soil and infect the new crop when an opportunity comes,
so that in control all rotted tubers should be discarded
for planting.

Silver scurf

This is caused by the fungus Spondylocladium atro-
virens, recently introduced from Europe, and has been
commonly observed in the United States. It shows as
dark spots or areas on the surface of the tuber. In these
areas fine black points are found which make up the spore-
bearing area. The fungus destroys the skin so that the
moisture escapes and the affected tuber shrinks badly.
The affected areas at this time and even before have a
silvery luster, a character which gives the disease its
name. The market value of such tubers is lessened, and
they should not be used for planting, as seed treatment
is apparently ineffective in destroying the fungus.

Potato ivart

This disease, caused by one of the lower forms of
fungi called Synchitrium endobioticum, does not appear in
the United States and should continue to be kept out by
strict quarantine measures. The disease has been known
in Hungary since 189G. It has been found in many
European countries and also in Newfoundland. It is
reported to be very destructive and is very difficult to
control, a long rotation of crops being the only measure
recommended.

198 The Potato

The fungus causing the disease gains entrance into the
eyes, which become black and swollen. "In more ad-
vanced stages one or more nodules, varying in size from
that of a wrinkled pea to a lump as large or larger than
the tuber itself, may be found. These are green where
they project from the ground and white below, turning
as they grow old to dark brown or almost black. They
have a wrinkled coral-like appearance like the head of a
cauliflower. 'A still more advanced stage occurs when
the fungus has utilized every particle of food stored in
the tuber and has reduced it to a brownish black soft
mass, giving off a very unpleasant putrefactive odor.'
Such potatoes cannot be harvested whole. The black
pulpy mass breaks up, liberating millions of sporangia
(spore-sacs) which live for years in the soil. These
sporangia have been known to infect potato crops after
an eight-year interval." ^

Common scab

Common scab, caused by a soil bacterium, Actinomyces
chromogenus, is too well known to require detailed de-
scriptions. The organism affects only the outer layers of
cells, though there are deep scabs supposed by some to
be caused by the same organism. It has been shown
that gnats and possibly other insects may be responsil)le
for the original deeper injury, though the scab may also
be present.

The scab organism winters over on the scabby tuber, but
may also live from year to year in the soil. Badly scabbed
tubers should not be planted. Clean tubers, as well as
those not badly scabbed, after being treated may be

» U. S. D. A.. Farmers' Bui. 489.

Plate XII. — Spindling potato sprouts ; upper picture, the disease

rhizoctiniose.

(Courtesy Dept. of Plant Pathology, College of Agriculture, Cornell University.)

Diseases of the Potato 199

planted on land where crops have been rotated. Lime,
wood ashes, manure and other materials giving alkaline
reaction should not ordinarily be used on potato soil in
connection with the growing of that crop. If it is neces-
sary to apply any of these substances in order to grow
other crops the application should be made in the fall
after digging the potatoes. Manure may be applied best
as a top dressing to the meadow.

Black-leg

This disease, which is caused by the bacterium Bacillus
phytophoni^, affects the vines and tubers. Infected
vines have a lighter green color than is usual and have a
stiff upright growth instead of the normal spread of foli-
age. The leaflets have a tendency to roll about the mid-
rib. The plant also may be smaller than it would natu-
rally be, though this is not always so. The base of the
stem is quite black and somewhat shriveled. The
diseased area commonly extends two or three inches
above the ground, sometimes much farther. It also
extends downward to the old seed tuber and may extend
into the stolons and young tubers.

The affected tubers may show a stem-end black-rot,
and when cut lengthwise sometimes show a black, foul-
smelling center decay and even a hollowed condition.
This center decay may be present with little evidence of
it at the surface.

The disease is distributed mainly- by affected seed
tubers, or by bruised, cracked or decayed tubers harbor-
ing the organism. Control consists in the selection of
seed tubers from healthy plants, in discarding bruised,
cracked and rotted tubers, and in seed treatment.

200 The Potato

Bacterial wilt

Bacterial wilt, caused by the bacterium Bacillus
solanacearum, is a disease that affects potatoes, tomatoes,
eggplants and a few other solanaceous plants. It occurs
mostly in the southern United States. The vines wilt sud-
denly, often on a single stalk, but later affecting the entire
plant. The stems lose their bright green color and be-
come shriveled and blackened. The vascular tissues, at
an early stage, have a brown color somewhat similar to
that described for Fusarium wilt. This color can be
seen through the outer cells and extends upward as nar-
row black streaks, even out upon the leaf petioles and
vines. When such stems are cut across, tiny drops of
liquid ooze out of the vessels at the cut surface. These
are of a dirty or yellowish white color, but not sticky or
foul smelling. Examination with a microscope shows
them to be swarming with bacteria.

This discoloration of the stem extends downward into
the stolons and tubers. A section across an infected
tuber at the stem end usually shows a blackening of
vessels, making a dark ring around the cut surface of the
tuber near the periphery. Bacteria similar to those
found in the stem are present in these vessels of the tuber
and later invade the other tissues, finally rotting the
entire inside of the tuber.

The bacillus is carried from infected to healthy plants
by insects that infest the potato vines. Probably this
is the common means of dissemination. Control, there-
fore, would consist in destroying the insects as far as
possible and in the early removal of infected plants from
the field.

Diseases of the Potato 201

Powdery scab (Plate XI)

Powdery scab is a disease of the tuber which is caused
by a sHme-mold, Spongospora suhterranea. It may be
easily observed at an early stage in young tubers as
brownish colored blisters. These, later, show as pits
filled with a brown powder, the spores of the parasite.
These pits are bordered by the torn skin of the tuber.
In storage the slime-mold may continue to be active,
causing a dry sunken rot about the pit. A cankerous
stage of the disease has been described as occurring in
low, wet lands, in which case the deeper tissues of the
tuber are invaded by the slime-mold and by other organ-
isms, so that it becomes badly rotted. The disease has
not been serious in the United States, and its develop-
ment seems to be arrested in the warmer potato sections.

The parasite is disseminated by the distribution of
affected tubers and by any agent upon which the spores
may become lodged. The disease is difficult to control,
but it is said to be materially reduced by seed treatment
and rotation of crops. Affected tubers should be de-
stroj^ed by burning or by boiling, and no tubers, even
though healthy, coming from fields known to be infested
should be used for planting.

Tip-hum

This is a disease characterized by a browning and
shriveling of the tips and margins of the leaves. The
trouble may become quite severe and greatly reduce
the yield of tubers. It is often confused with blight, but
it is not due to parasites, but to hot, dry weather follow-
ing a period when the conditions of temperature and

202 The Potato

moisture favored a rapid growth of the vines. Cultural
practices that aid in the conservation of moisture com-
bined with frequent applications of bordeaux mixture
will reduce the amount of leaf-area injured.

Arsenical injury

This is a burning caused by a heavy application of
paris green or other insecticides containing free arsenious
acid. The injury often resembles early blight, but is
lighter colored and usually occurs about flea-beetle punc-
tures or other injuries to the leaf, while early blight spots
may occur on the otherwise uninjured leaf. The neces-
sary amount of the more caustic poisons used with bor-
deaux mixture or with equal parts of lime should cause no
burning.

Spindling sprout (Plate XII)

Spindling sprout is a disease characterized by very
small, weak, needle-like sprouts coming from the eyes
instead of large vigorous ones. Vines from such sprouts
remain small and weak and only small unmarketable
tubers are produced from such hills. It is believed that
tubers becoming unduly heated by the hot soil during
their growth produce sprouts of this character. If this
is true, northern-grown seed is less likely to be affected.

Net necrosis

This name is applied to a diseased condition of tubers in
which brown streaks occur within the tuber. These
streaks are confined largely to the vascular system, though
they do not appear as a dark ring on the surface of a cut
across the tuber as is usually the case with other vascular

Diseases of the Potato 203

diseases, but they may also be found within the central
area of the cut surface. They may be found throughout
the length of the tuber or be confined to the stem end.
The exterior appearance of the tuber gives but little
indication of conditions within. The vines also become
affected, but the symptoms have not been studied care-
fully enough to differentiate them from those of wilt
disease. No organism has been found associated with
the streaks in the tubers, but an organism has been found
associated with affected stems and roots. Affected tubers
should be discarded for planting as they may produce
weak plants, but they are not unfit for food. The same
or a similar disease is known in England as "Sprain"
and in Germany as " Eisenfleckigkeit."

Curly dwarf

Curly dwarf is a non-parasitic disease characterized
by a wrinkling and curling of the leaf-blade about the
veins and midribs. Affected plants are usually dwarfed
and die earlier than healthy ones, though all stages of the
disease may exist in a field, and in some plants it may be
so slight as to be hardly noticed. The yield in advanced
cases is very much reduced. Tubers from affected
plants, while they show no evidence of disease when
planted, will produce vines that show a more advanced
stage of the disease. Since the presence of the disease
is partly responsible for reduced yields, no tubers from
affected vines should be planted. The elimination of
these can best be accomplished by inspection of the
vines in the field about blossoming time of the plant, at
which time affected hills should be removed or marked
for removal.

204 The Potato

Mosaic

This disease is characterized by a crinkhng of the
fohage and by a mottled condition due to numerous small
areas of the leaf-blade having a lighter green color than
is usual. In some plants this is not especially notice-
able, for there are all gradations from healthy plants to
badly diseased ones. The disease is more commonly
found on white sprout varieties and is said to reduce the
yield materially. Since, like curly dwarf, it is transmitted
by means of the tuber, the same selection should be prac-
ticed.

Leaf-roll

Leaf-roll is the name given to a non-parasitic disease
of the plant and is characterized by a dwarfing and a
yellowing of the vines and by an upward rolling of the
leaflets about their midrib. The leaves have a tendency
to point upward and are rather stiff to the touch. There
are, perhaps, several types of the disease. In one type
the lower leaves at first show a tendency to roll and be
stiff though the plant is otherwise normal in appearance.
In another type the foliage has a yellowish cast. The
leaflets of the upper and younger leaves point upward
and roll and often show a rose or light purple color at the
lower margins. There are all gradations of the disease,
and the well-marked t^-pes show great reduction of growth
and yield. The disease is transmitted by means of the
tubers, so that rigid selection in the field is necessary to
avoid it.

The cause of curly-dwarf, mosaic and leaf-roll is un-
known. Many theories have been advanced to explain
them, but it is unnecessary to discuss them here. All

Diseases of the Potato 205

three diseases are evidently widespread and may be
important factors in causing reduced yields and "running
out" of potatoes. Tubers from such vines are usually
small. For this reason the selection of small tubers from
the bin is likely to increase the percentage of such affected
plants. It is possible to avoid them by the selection out-
lined in the chapter on Control Measures.

Constitutio7ial degeneracy and other weakened conditions
of plants

Constitutional degeneracy is a name given to a condi-
tion of weakness of growth showing as small, often spin-
dling stems producing but a few small tubers to a hill.
Such a condition is inherent in the plant and is inherited
by the progeny. This trouble may be confused with
similar conditions associated with the non-parasitic
diseases already enumerated. Very small, spindling
plants producing no commercial tubers are often found
to be associated with an early rotting of the seed tuber
after being planted, and similar plants sometimes appear
when the only eye on the piece of tuber is near the cut
surface. Rotting of tubers may be due to such prac-
tices as keeping cut tubers undusted a week or more
before planting and as planting cut tubers in hot soil or
leaving them exposed to the sun after hand-planting.
Avoiding such practices may be of assistance in reducing
the number of weak plants in the field, but tubers from
degenerate hills should never be used for seed. The
elimination of these can be accomplished to some extent
by grading, but selection from the field is the surest way.

CHAPTER XI

CONTROL MEASURES AGAINST DISEASES

By M. F. Barrus

It will be noticed from reading the preceding pages
that for some diseases the selection of seed tubers is
advised and for others seed treatment, crop rotation or
spraying is recommended. It may be necessary to prac-
tice more than one control measure in order to control
some diseases. P'or the seed potato grower, it is desirable
and is becoming more and more necessary that all meas-
ures be employed that will tend to produce sound tubers
free from all diseases. Detailed directions for carrying
out these measures are given in these pages.

Control of curly-divarf , mosaic and leaf-roll

As has already been pointed out, such diseases as curly-
dwarf, mosaic and leaf-roll, transmitted by the tubers,
cannot be detected by the appearance of the tuber out-
side or within. There is very little or no outward evi-
dence on tubers affected with Fusarium and ^^erticillil^n
wilt, bacterial wilt and net necrosis, and occasionally on
some tubers affected with black-leg. Even a section of
the stem end will sometimes fail to reveal the presence
of these last-named diseases. In such cases, it is very
206

Control Measures 207

necessary, if these diseases are to be avoided, to inspect
the field one or more times during the growing season in
order to detect the affected hills from the appearance of
the vines. If only one inspection can be given, this should
be made at about the blossoming time, because the non-
parasitic and other troubles can be best detected at this
time. A second inspection before the vines die will often
reveal diseased vines that could not be seen earlier. At
the time of inspection all diseased hills should be marked
for removal before digging the others in order that they
may not be mixed with them. If there is a considerably
large percentage of them, more than 10 or 15 per cent,
the crop should not be used for commercial seed purposes.
The grower, however, may select from such a field plants
that are healthy for his own seed, and these should be dug
before the others and stored by themselves.

Field inspection

The grower may feel that he is unqualified to do such
inspection himself, but certainly he can detect poor hills,
and with a little instruction from an expert can learn to
distinguish the various diseases. If, however, individual
farmers growing seed potatoes for sale make their own
inspections, there will be a great diversity of standards,
hence it is more practical for one man to inspect all the
fields in a certain locality. Such a man should be trained
for the work. He may be employed by an association of
potato-growers or by some other organization, or he may
be an official inspector of the state or country employed
to inspect fields, and tubers after digging, for the purpose
of certifying them. Some such method will greatly im-
prove the seed stock, and the grower of such stock will

208 The Potato

not only be able to secure better prices, but will increase
his own yields because of the use of better seed. The
time will not be long before the southern potato-grower
will demand seed tubers certified by some responsible
organization, and poor seed will find a market for table
stock or some other purpose.

Not all the vines thought to be healthy in the field will
produce satisfactory seed tubers. There may be hills
among them that produce a small number of marketable
tubers, and these should be eliminated from seed stock, if
possible. However, this can be done only by digging
each hill separately and selecting tubers from desirable
hills, as explained in an earlier chapter. Growers should
do this whenever possible to improve their own seed, but,
to improve further the seed stock for sale, much can be
done by grading because of the small tubers, many of which
come from weak or diseased hills. Growers at planting
time should discard all rotted, bruised or badly scabbed
tubers, for these are not as satisfactory as healthy, smooth
ones, even when treated.

Seed treatment to prevent disease

Seed treatment as directed will destroy organisms living
on or anchored on the surface of the tuber. For this
reason, it is to be advised when such diseases as com-
mon scab, powdery scab, rhizoctoniose and black-leg are
troublesome. Treated tubers often give a better stand
because rot organisms, ordinarily saprophytic, found on
the surface of the tuber are destroyed. Treating the
seed also eliminates the danger of introducing disease
organisms into new soil or soil that has been freed from
them to a greater or less extent. Few growers have

Control Measures 209

believed that these organisms introduced with the seed
affect not only the crop of that year but remain in the
soil to attack subsequent crops of the same or other kinds.

Treating seed tubers is not as troublesome as some
farmers think. The treatment, if desired, can be made
several weeks in advance of planting, but less handling is
necessary if it is made immediately before cutting. Where
one has only one hundred bushels or less to be treated, it
is convenient to place two or more barrels on a platform,
which should be high enough to draw the solution off
through a hole near the bottom of the barrel. The pota-
toes are dumped into the barrels and are covered with
the solution, which may have been prepared in another
barrel. One barrel of solution will cover two barrels of
potatoes. After they have soaked the required length of
time, the solution may be drawn off at the bottom and
emptied into the barrel in which it was prepared. The
treated tubers can now be emptied on to the ground to be
dried, but care should be taken that they are not over-
heated by the sun. The barrels can be filled again with
potatoes and the same solution used once more. While
waiting for this lot to soak the tubers already treated
may be cut for planting. This saves time. By using
two barrels, it is possible for one man to treat about 50
bushels of potatoes in a day and have time to cut tubers
for planting between treatments. Two men can treat
about 250 bushels in one day by the use of 10 barrels
in making the treatment.

Either formaldehyde or corrosive sublimate may be
used. The former is much cheaper, less poisonous and
can be used in metal vessels if desired, but it is not as
effective in destroying the sclerotia of Rhizoctonia as cor-
rosive sublimate. A pint or pound of 40 per cent form-

210 TJie Potato

aldehyde, costing about 30 cents, should be diluted with
30 gallons of water. This can be used over and over
again for at least ten times without losing strength, but
the quantity will, of course, be diminished with each treat-
ment. The tubers should be soaked in it for two hours.
A longer time may injure the sprouting power of the tuber.
When corrosive sublimate is used, four ounces of the dry
powder, costing about 50 cents, should be used to 30
gallons of water. The powder should first be dissolved
in a quart or two of warm water and then added to the
other. It dissolves more slowly in cold water. The solu-
tion should not come in contact with metal, as it reacts
with it and loses strength. Neither should it be used
more than three times in treating potatoes unless renewed
with fresh solution, for it loses its strength rapidly with
use. Tubers should be soaked in it for at least one and
one-half hours, but never longer than five hours. Great
care should be taken in its use, for it is exceedingly poison-
ous. Treated tubers should never be used as food.

Where one has large quantities of tubers to be disin-
fected at one time, the formaldehyde gas treatment may
be used. For this purpose the tubers should be placed in
crates or in shallow slatted bins so as to permit the free
movement of gas about them. The disinfecting room
should be made as air-tight as possible. Spread potas-
sium permanganate evenly over the bottom of a large
deep pan or bucket. Twenty-three ounces should be
used for each 1000 cubic feet of space within the room.
Pour over the permanganate three pints of 40 per cent
formaldehyde for each 1000 feet of space. Give the pan
a tilt, leave the room as quickly as possible, and close the
door tightly, leaving it closed for 24 hours or, at least, over
night. The door can then be opened and the room aired

Control Measures 211

out, after which the potatoes may be handled as any
other treated tubers. The following recommendations
should be observed by those using this method. Make
the treatment before the potatoes sprout. Place the
generating pan so that no potatoes are within three feet
of it and none directly above it. Use at least 167 bushels
of potatoes for each 1000 cubic feet of space or injury
will result to the tubers. This injury shows as a pitting
about the lenticels. Do not attempt treatment when the
temperature of the room is below 50° F. It is most
affective at 80° F. Thoroughly wet the floor of the dis-
infecting room with boiling water just before adding the
formaldehyde to the permanganate, as moisture in the air
of the room is very essential for effective work. Do not
attempt to treat potatoes in sacks or piled high in bins.

The question often arises as to whether the crates or
bags in which the tubers are to be carried to the field
should be sterilized or whether cutting-knives should be
often disinfected. It is possible for spores of the organ-
isms causing potato diseases to be carried on containers
or implements and later come in contact with the tuber
under such conditions that infection may take place.
The writer is of the opinion that infection in this manner
does not frequently take place, but if one desires to avoid
every possible contamination, this disinfection will be
necessary. It may even be desirable when such diseases
have been very troublesome, but ordinarily it is not neces-
sary, although one should use judgment in the matter.

If potatoes are cut more than a few days in advance of
planting, they should be dusted to prevent decay from
the action of saprophytic bacteria under favorable con-
ditions of heat and moisture. While other kinds of dust
will prevent the decay, flowers of sulphur is preferable as

212 The Potato

it has fungicidal properties. Indeed, it has been shown
that when sulphur is used in sufficient quantities, it aids in
the reduction of powdery and common scab. Gypsum
makes a satisfactory material for dusting, but lime in any
form should not be used for this purpose as it may induce
scab.

Disease from organisms already in soil

It must be remembered that seed treatment, while it
destroys certain pathogenic organisms on the surface of
the tuber, does not insure immunity of the crop from these
diseases. Many of these organisms also live in the soil
from year to year, and these are as able to attack plants
coming from treated as from the untreated seed. The
treated seed must be planted in soil that is free from these
organisms or where they are much reduced or in an in-
active condition. It is impractical to sterilize soil for
growing potatoes, although for greenhouse and other
valuable crops it is considered to be a good practice.
The application of chemicals to the soil that will destroy
or retard the growth of these organisms has not given
very satisfactory results. Sulphur applied at the rate of
450 to 900 pounds to the acre has reduced the amount of
scabby tubers to a considerable extent, but it may also
reduce the yield. It has been observed that clover will
not grow in soil treated in this way. Fertilizers such
as lime, which increase the alkalinity of the soil, greatly
favor the development of scab, while acid phosphate, sul-
phate of ammonia and the like, at least, do not increase
scab injuries.

When potatoes are grown year after year upon the
same land, the parasites, especially those that live in the
soil, are likely to increase unless one constantly guards

Control Measures 213

against them. On the other hand, if the potato crop is
alternated with other crops or can be grown in a three-
to five-year rotation, these parasites depending upon the
potato for food will be starved out during the intervening
years. Unless such parasites are introduced again by
planting affected seed, or with manure containing these
organisms, or with infected soil washed or carried on to
the land, the potato crop planted in a rotation should be
comparatively free from them.

This would be the case were it not the habits of some
organisms like Rhizoctonia to live on hosts other than
the potato, or of others like the scab organism to live
from year to year on dead organic matter in the soil.
However, a rotation aids in reducing these organisms
when they are troublesome, and for this reason, if for no
other, should be practiced when possible.

Often there are a large number of missing hills in a
field caused by the decay of the seed tuber from attacks
of Rhizoctonia, or for other reasons, causing the total
yield to be materially reduced. This is especially true
when the tubers are planted in hills or at distances greater
than 18 inches in the row. When the tubers are planted
close together, a missing hill does not mean a complete
loss, because the neighboring hills, having more room for
growth, w^ill produce a larger yield. Some farmers have
found it profitable to replant missing hills with tubers
that have been greened, i.e. left in the light so that they
have stubby green sprouts. Such tubers when planted grow
rapidly and are not much later than the ones planted first
and not greened. Greening potatoes is a good practice, for
such tubers will give a better stand than those not greened.

There are diseases, such as early and late blight, that
occur under favorable weather conditions and do much

214 The Potato

damage even though the seed has been carefully selected
and treated and other precautions taken.

Treatment for potato blight

The blight-rot fungus is not destroyed by seed treat-
ment, and slightly affected tubers may be overlooked in
sorting. Blight spores, being easily carried by air cur-
rents, are readily disseminated from one field to another
and bring about an infection if wet weather prevails. It
must be remembered that the tubers are infected by
spores produced on blighting vines. Hence, to prevent
this rot from occurring, it is necessary only to prevent
the vines from blighting. The vines will not blight, even
under very favorable weather conditions, if the spores do
not gain entrance into their tissues. The spores cannot
enter the leaves if the vines are thoroughly sprayed with
bordeaux mixture before the spores have germinated.
As they germinate only in the presence of moisture, the
applications need be made only before moist conditions
prevail, that is, before rainy periods. "The grower should
not hesitate to spray at such times for fear that the mix-
ture will be washed off. It dries rapidly, and once dried
on the vines, enough remains even after heavy rains to
protect them from the fungus."

Every susceptible part of the vines should be protected
by the mixture. To do this eflFectively, it is necessary
that the mixture should come from the nozzle as a fine
mist and settle over every leaf and stem like a fog. Such
a mist can be produced with a satisfactory nozzle and
with good pressure.

One application thoroughly done will protect the parts
receiving it for a long time, but new leaves appear, and

Control Measures 215

these must be protected by subsequent applications.
These applications should be continued as long as growth
of the vine takes place. Even when the vines cover the
space between the rows and driving through will injure
them, the spraying must be done. Less loss will result
from injured vines than from rotted tubers. On loamy
ground, the injury to the vines is not so great as one would
think. Some ingenious farmers have devised a means of
pushing the vines away from the wheels by attaching rake
teeth on each side of each wheel. Manufacturers of
spraying machinery should be able to devise some means
of overcoming this objection to spraying.

From five to eight applications, depending upon weather
conditions, should be made during the season. The first
should be given when the plants are six to eight inches
high or when a poison is applied to kill the bugs. For
the early applications 50 to 75 gallons of mixture to the
acre will be sufficient, but later in the season it will re-
quire 100 gallons or more. Enough should be applied to
do a good piece of work even though it takes 150 gallons.
The operator should determine this. Nozzles capable of
delivering this amount of liquid as a mist must be the
only kind employed, although pressure has much to do
with fineness of the mist. From 70 to 80 pounds of
pressure will make a fine mist with vermorel nozzles if
there are not too many used at a time, while it will take
100 to 150 pounds of pressure to get a good mist w^ith an
equal number of disk nozzles. But the vermorels do not
have the capacity that disk nozzles do and more are re-
quired to do the same work. One disk nozzle will do
good work at first, but two should be employed later on
and then should be so adjusted that the spray is directed
at an angle rather than straight down upon them. The

216 The Potato

pump of the machine should be capable of maintaining a
uniformly high pressure. These are factors that must be
considered in buying or constructing a machine. Other
points are of secondary importance. For small fields of
an acre or less, a small compressed air spray may be used.

The operator should see that the mixture gets on to the
vines. It is of little value applied to the soil. It occa-
sionally happens that a nozzle becomes clogged, and the
vines below are not being properly sprayed. One cannot
hope to spray a field adequately by merely driving through
it. Much depends on the interest taken by the driver.
One can best determine whether the application is thorough
by examining the vines after spraying them.

Various strengths of bordeaux mixture have been
recommended. The 5 : 5 : 50 formula is commonly used
on potatoes. Experiments have shown that the spores
of the blight fungus can be prevented from germinating
at a much weaker strength, so that there is little doubt
that the blight can be controlled with bordeaux mixture
at 2 : 2 : 50 or 3 : 3 : 50. When copper sulphate is very
expensive, as at present, larger profit can doubtless be
secured with a weaker mixture than with a stronger one,
which may give slightly increased yields from greater
stimulation.

For many years potato spraying experiments have
been conducted in several states. The bordeaux mix-
ture has been prepared in various ways, and used at
different strengths. The experiments have been con-
ducted on experiment station grounds and on farms in
various parts of the country. These applications have
been made by scientific men and by farmers with hand
machines and with traction sprayers. The conclusion in
nearly every case has been that it pays to spray with

Control Measures 217

bordeaux. There have been years when certain fields
have shown no increase from spraying, but usually a suffi-
cient increase has been obtained, if the spraying has been
well done, to pay for the cost of the applications. Even
in years when the blight is absent, the application of bor-
deaux appears to stimulate the vines, for they are greener
and remain alive longer than unsprayed vines. Bordeaux
also acts as a repellant to the flea-beetle and reduces the
amount of tip-burn and so protects the leaves from vari-
ous injuries. In years when blight is present, the evi-
dence is greatly in favor of spraying. One cannot tell
with any certainty when blight will come, so one should
practice spraying as a protection. Growers should accept
the evidence and make spraying of potatoes with bordeaux
a general farm practice every year whether wet or dry on
both early and late varieties.

Preparation of hordeailx mixture (See Plate XIII)

Bordeaux mixture can be purchased on the market as
a paste or powder. Usually most of the proprietary mix-
tures contain in addition an arsenical poison for killing
biting insects. They are prepared for spraying by the
simple addition of water to a given quantity of material.
For this reason they are convenient to use and also safer
when one needs to depend on irresponsible help to do the
work. However, these do not stay in suspension as well
as bordeaux properly made at home, and they are more
expensive. Home-made bordeaux, according to most
comparative experiments, is the most satisfactory. Its
preparation is easy and inexpensive and one requires but
a short time, when the apparatus for making it is once
constructed. The following directions with a few addi-

218 The Potato

tions are taken from the New York Cornell Agricultural
Experiment Station, Circ. 19, 1913.

The best bordeaux mixture is made by mixing a dilute
solution of copper sulphate (blue vitrol) with a dilute milk-
of-lime. The mixture may be made of various strengths
by using different amounts of copper sulphate and lime to
a given amount of water. A combination of 3 pounds
of copper sulphate and 3 pounds of lime to 50 gallons
of water is probably strong enough to control the blight,
but because of the stimulating action of bordeaux mixture
on the potato plant, a strength of 5 pounds each of
copper sulphate and lime to 50 gallons of water is usually
recommended. This is indicated by the formula 5 : 5 : 50.
In order to make the bordeaux mixture of any strength,
the procedure should be as follows : —

A stock solution of copper sulphate should be made in a
barrel from 45 pounds of copper sulphate dissolved in 45
gallons of water. A gallon of the solution will then con-
tain about one pound of copper sulphate. If the crystals,
placed in a gunny sack, are suspended so as to be slightly
beneath the surface of the water, they will dissolve in
three or four hours.

A stock mixture of lime should be made from a bushel
of good stone lime placed in a barrel and slaked by the
gradual addition of water. Care must be taken not to
"drown" the lime. When it has become pulverized by
the slaking, water is added to make a paste, and then
enough more water may be added to make 45 gallons.
This should not be allowed to dry out. Hydrated lime
(which is already slaked) may be used in place of stone
lime, but air-slaked lime should never be used.

Another barrel or larger container or even the sprayer
tank itself may be used for mixing the bordeaux. What-

Control Measures 219

ever container is used should be filled three-fourths full
of water. If a 5 : 5 : 50 solution is desired, 5 gallons of
copper sulphate stock solution should be added to this
water for every 50 gallons of mixture to be made. The
solution requires stirring until it is well diluted, after
which 5 gallons of the stock mixture of milk-of-lime should
be added to each 50 gallons of mixture. The lime-water
should be run through a strainer in order to prevent the
larger particles of lime from getting into the sprayer tank.
While the milk-of-lime is being added to the dilute copper
sulphate solution in the sprayer tank, the material in the
container should be stirred constantly. The sky-blue
bordeaux mixture will result. Enough water to make the
required amount of mixture must be added to it.

It is often more convenient, although not necessary, to
make the bordeaux on an elevated platform so as to allow
the mixture to run by gravity into the sprayer tank (see
Plate XIII). When such a platform is provided, it is easily
possible to dilute both the stock copper sulphate solution
and the stock lime solution in separate containers before
mixing them by allowing them to run together. This
method makes a bordeaux that stays in suspension a little
better than that made by diluting but one stock before
mixing. In case the latter method is used the required
amount of stock in each case should be diluted with one-
half the amount of water necessary to make the mixture.

The mixture should now be tested with a few drops
of a solution of potassium ferrocyanide. This is made
from crystals of potassium ferrocyanide dissolved in soft
water. Five cents' worth of crystals dissolved in a pint of
water will provide enough of the solution to last through-
out the season. Should a brown precipitate result when
a few drops of this solution are added to the bordeaux

220 - The Potato

mixture, it would indicate that more lime-milk is needed
to neutralize the copper sulphate solution. When suffi-
cient lime is added, no brown precipitate will be formed
by the potassium ferrocyanide solution. Bordeaux mix-
ture will burn the foliage of plants if it is not properly
neutralized. It is unnecessary to measure the milk-of-
lime in making bordeaux mixture if the mixture is tested
from time to time with the ferrocyanide solution while
adding the lime. The test will indicate when sufficient
lime is present.

When it is necessary to spray with a poison in order
to kill potato beetles and other biting insects, the re-
quired amount of poison may be added to the bordeaux
mixture.

Other remedies

Soda bordeaux, in which an equal amount of sal-soda is
used in place of lime, has been employed by some potato-
growers, but carefully conducted experiments indicate
that other preparations wdth copper compounds are in-
ferior to lime. Dry bordeaux applied as a dust has not
proved to be a satisfactory fungicide. Lime sulphur solu-
tion is also unsatisfactory and unsafe. Where it has
been used in experimental work, potato plants sprayed
with it have given smaller yields than the unsprayed ones.
Powdered sulphur and arsenate of lead or arsenate of zinc
have been tried in New Jersey on early potatoes, but have
been found to be less satisfactory and more expensive
than bordeaux mixture.

Fusarium dry rot and other rots are caused by organ-
isms that gain entrance to the tuber through wounds.
Potatoes with tender skin loaded into cars in hot weather
soon after digging often rot badly. Care in handling the

Control Measures 221

tubers is necessary if one wishes to avoid these troubles.
Provisions for ventilation should be made when the tubers
are placed in storage. A potato tuber contains living
protoplasm which gives off carbon dioxide, water and
a certain amount of heat, and when provision is not made
for ventilation, black-heart or center decay may occur.

Disease-resistant varieties

These various control measures have been discussed
because it is necessary to adopt some or all of them if one
is to grow healthy tubers. However, each practice adds
to the cost of producing the crop. If such measures do
not increase the yield or add to the value of the tubers,
they are not worth putting into practice. If it were pos-
sible to obtain potatoes that would not become diseased
even when subjected to the parasite under favorable con-
ditions for infection, much labor and expense would be
saved. It is well known that certain individual plants as
well as animals have shown marked resistance to diseases
that ordinarily occur on their kind. By selection and
breeding, it has been possible to obtain highly resistant
plants producing crops of good quality. Notable ex-
amples are wilt-resistant melons, cotton and flax, rust-
resistant wheat and anthracnose-resistant beans. For
several years scientists have been endeavoring to secure
a satisfactory strain or variety of potatoes that is blight
resistant. Some varieties have been secured that have
shown a fair degree of resistance to blight or rot. Unfor-
tunately, a variety that seems to show a slight degree of
resistance to blight may show considerable susceptibility
to rot, and varieties showing resistance to early blight
may be subject to late blight. William Stuart of the

222 The Potato

Department of Agriculture, Washington, D. C, has
reported certain varieties that have shown considerable
resistance to both early and late blight. These are
Apollo, Sophia, Professor Wohltman and Max Eyth.
They are all foreign varieties and under conditions of
climate and soil in the United States they succeed very
poorly, being light yielders and rather poor in quality.
Stuart remarks that it would seem as if high disease-
resistance of the vine was correlated with low yield and
undesirable tubers. He found no varieties tested to have
strongly marked scab-resistant qualities when grown in
soil well infested with the scab organisms. He believes
that the value of disease-resistant varieties is problem-
atical, but that the plant-breeder, by mating them with
the most desirable commercial American types, may
develop commercial types of resistant varieties.

Summary

It may be well to summarize control measures in the
following way : —

What selection does. — It aids in eliminating curly-
dwarf, leaf-roll, mosaic, the various wilts, black-leg and
other diseases showing on the vines and also transmitted
by the tuber. It eliminates low-yielding hills. It elimi-
nates impurities in a variety.

What seed treatment and rotation do. — They reduce in-
jury from rhizoctoniose, scabs and black-leg. They
increase the stand of potatoes in the field. They give
clean tubers.

What spraying does. — It prevents early and late
blight. It prevents the blight rot. It reduces injury
from tip-burn. It repels flea-beetles. It kills the bugs.

Control Measures 223

It stimulates the vines to longer periods of growth. It
gives increased yields.

REFERENCES

DUGGAR, B. M.

1909. Fungous Diseases of Plants. (Ginn & Co.), 1-508, Figs.
1-240.
Gloyer, W. O.

1913. The Efficiency of Formaldehyde in the Treatment of Seed

Potatoes for Rhizoctonia. New York (Geneva) Agri.

Expt. Sta. Bui. 370 : 417^31, pi. 1.
Jones, L. R.

1899. Certain Potato Diseases and Their Remedies, Vt. Agri.

Expt. Sta. Bui. 72 : 3-32, Figs. 1-17.
Jones, L. R., Giddings, N. J., and Lutman, B. F.

1912. Investigations of the Potato Fungus. Phytophthora

Infestans. U. S. D. A., Bur. PI. Ind., Bui. 245 : 5-100,

Figs. 1-10.
Lutman, B. F.

1911. Twenty Years Potato Spraying for Potato Disease.

Potato Diseases and the Weather. Vt. Agri. Expt.

Sta. Bui. 159 : 215-296.
Lutman, B. F., and Cunningham, G. C.

1914. Potato Scab. Vt. Agri. Expt. Sta. Bui. 184 : 3-64, Figs.

1-6, pis. 1-12.
Mann, Thos. F.

1911. The Fusarium Blight Wilt and Dry Rot of the Potato.
Ohio Agri. Expt. Sta. Bui. 229 : 229-336, pis. 1-15.
McAlpine, D.

1911. Handbook of Fungous Diseases of the Potato in Australia
and Their Treatment, with 158 figures. Dept. of Agri-
culture, Victoria.
Melhus, L E.

1913. Silver Scurf — A Disease of the Potato. U. S. D. A., Bur.

PI. Indus., Circ. 127: 15-24, Figs. 1-4.
Melhus, I. E.

1914. Powdery Scab (Spongospora subterranea) of Potatoes.

U. S.^D. A., Bui. 82 : 1-16, pis. 1-2.

224 Tlie Potato

Melhus, I. E.

1915. Hibernation of Ph\i;ophthora Infestans of the Irish Potato.

U. S. D. A., Jour, of Agri., Research Bui. 5 : 71-102, Figs.
1-3, pis. 4-8.
Melhus, I. E.

1916. Germination and Infestion with the Fungus of the Late

Blight of Potato. Wisconsin Agri. Expt. Sta., Research
Bui. 37: 1-64, Figs. 1-8.
Morse, W. J.

1909. Black-leg — A Bacterial Disease of the Irish Potato.
Maine Agri. Expt. Sta. Bui. 174 : 309-328.
Morse, W. J., and Shapovaloy, M.

1914. The Rhizoctonia Disease of the Potato. Maine Agri.
Expt. Sta. Bui. 230 : 193-216, Figs. 61-73.
Morse, W. J.

1914. Powdery Scab of Potatoes. Maine Agri. Expt. Sta. Bui.
227 : 89-104, Figs. 44-50.
MuNN, M. T.

1912. Lime Sulfur vs. Bordeaux Mixture as a Spray for Potatoes.

Part II. New York (Geneva) Agri. Expt. Sta. Bui.
352 : 319-326.
Orton, W. a.

1913. Potato Tuber Disease. U. S. D. A., Farmers' Bui. 544 :

3-16, Figs. 1-16.
Orton. W. A.

1914. Potato Wilt, Leaf Roll and Related Disease. U. S. D. A.,

Bui. 64 : 1^8, pis. 1-14.
Smith, E. F., and Swingle, D. B.

1904. The Dry Rot of Potatoes due to Fusarium Oxysporum.
U. S. D. A., Bm-. Pi. Indus., Bui. 55 : 3-64, pis. 1-8.
Smith, E. F.

1896. A Bacterial Disease of the Tomato, Eggi)lant and Irish
Potato. U. S. D. A., Div. Veg. Phys. and Path., Bui.
12 : 3-25.
Stevens, F. L., and Hall, J. G.

1913. Diseases of Economic Plants. (The Macmillan Co.),
New York, 1-513, Figs. 1-214.
Stewart, F. C, French, G. T., and Sirrine, F. A.

1912. Potato Spraying Experiments — 1902-1911. New York
(Geneva) Agri- Expt. Sta. Bui. 349 : 99-139.

Control Measures 225

Stewart, F. C, and Gloyer, W. O.

1913. The Injurious Effect of Formaldehyde Gas on Potato

Tubers. New York (Geneva) Agri. Expt. Sta. BuL 369 :
385-416, pis. 1-2.
Stewart, F. C., and Sirrine, F. A.

1915. The SpindHng Sprout Disease of Potatoes. New York

(Geneva) Agri. Expt. Sta. Bui. 399 : 133-143, pis. 1-3.
Stewart, F. C.

1916. Observations on Some Degenerate Strains of Potatoes.

New York (Geneva) Agri. Exp. Sta. Bui. 422:319-
357, Pis. 1-12.
Stuart, Wm.

1914. Disease Resistance of Potatoes. Vt. Agri. Expt. Sta.

Bui. 179 : 147-173, Figs. 1-8.

CHAPTER XII
HARVESTING THE POTATO

There are several important considerations bearing
upon the harvesting of the potato crop. These must be
kept in mind when one is phmning the time and method
of harvesting, if the best returns are to be reaUzed. Im-
proper attention to any of these points may result in a
very material decrease in the crop.

In the first place, the harvesting should be done at such
a time and in such a manner as to give the maximum
yield of tubers possible for that season. This means that
we are to let the processes of starch formation and storage
go on as long as they will. Secondly, we should aim to
employ such methods as will give us potatoes of the best
cooking and keeping qualities. And thirdly, we must
eliminate, as far as possible, all traces of disease from the
crop. Each operation in the process of harvesting should
be carried on with careful consideration of its effect on
total yield, quality and disease.

Time to harvest

The time of harvesting is influenced by the weather
conditions and by the kind of potatoes grown. In general,
one does not need to be as particular with early potatoes
as with the late varieties. Early potatoes may be dug
as soon as they are large enough to eat. Late potatoes,
226

Harvesting the Potato

227

generally speaking, should be left in the ground as long
as is possible without freezing. It should be remembered
that starch is being formed and stored as long as the tops
of the plants are green. To harvest the crop before the
tops die, therefore, means a loss in quantity of potatoes.
Early varieties may be dug a week or two before maturity,
providing the higher price a bushel more than compen-
sates for the decrease in yield. Late potatoes, which
are usually stored for part or all of the winter, should
preferably be fully mature and in good condition when
harvested.

Kohler,^ of the Minnesota Experiment Station, presents
some interesting data on the results of digging potatoes
during the period of development. The variety on which
the studies were made was the Early Ohio. The tubers
were planted by hand on June 3, and the diggings were
begun about two months later and continued at intervals
of about a week, until the tops of the plants had died :

Table XII. — Results from Digging Early Ohio Potatoes
AT Intervals during the Period of Development

(In Bushels to the Acre)

Date op
Digging

IK

3

i
>

a

w
«

1

a

H

July 31

10.9

1.2

9.7

27.8

38.7

0

Aug. 7

7.5

62.3

—

3.3

30.5

28.5

25.4

87.7

1

Aug. 14

7.6

115.4

—

29.3

59.5

26.1

26.1

141.5

8

Aug. 23

7.2

182.1

6.7

42.9

97.3

35.2

21.1

203.2

22

Aug. 30

6.4

226.8

6.7

93.5

92.8

33.8

27.0

253.8

99

• Minn. Bui. 118.

228 The Potato

The plants took practically three months to mature.
Three weeks of this time were taken up in coming through
the soil. About five more weeks were consumed by the
crop in getting ready to produce tubers. Most of the
potatoes are produced during the last month of growth.
During this last month, there was a daily gain of about
7 bushels of marketable tubers to the acre — up to the
time the vines died.

The potatoes were classified as to size on the following
basis :

Small — 1§ ounces or less.
Near small — 2 ounces to 1^ ounces.
Medium — 5 ounces to 2| ounces.
Large — 9 ounces to 5 ounces.
Very large — over 9 ounces.

This table warrants the conclusion that potatoes should
be harvested after the tops die, if we are to secure the
highest yield. It also shows that there is a loss of yield
if we harvest the crop before it is mature, and that this
loss increases with the increase of time between the date
of harvesting and the time of maturity.

In the case of early potatoes, it is often possible to
obtain prices high enough to overbalance the loss in yield
and to make it profitable to dig them before they are
mature.

Table XIII has been arranged from figures given by
Kohler, to show relative prices at which potatoes should
sell if dug one and two weeks before maturity.

Potatoes which are harvested before the tops die and
before the tubers can be easily separated from the stems
are usually immature. Such potatoes are not up to the
American standard of quality for cooking, and are almost

Harvesting the Potato

229

sure to disappoint the buyer. The immature tubers are
also poorer in keeping qualities than those which have
matured on the vines.

Table XIII. — Early Digging for Market

Price when
Mature

Prices Which Must Be Obtained if Potatoes Are Dug

1 Week before Mature

2 Weeks before Mature

25 i
50)4

30^
Mi
63 ff

AH

59 ff
86)4

For several reasons it is best to harvest potatoes in dry,
cool weather. The tubers should be dug when the soil
is fairly dry, in order that they may go into storage
in a dry condition and as free from dirt as possible. The
cool weather prevents their wilting unduly and makes
it possible to get them into storage in good condition.
If the soil is not too moist, potatoes are best left in the
ground for a time after the tops have died, at least until
there is danger of a freeze. Most authorities agree that
no harm results from such a practice as long as the soil
condition is as described. In some sections this may be
almost necessary, especially where several weeks of warm
weather are likely to follow the dying of the vines. It is
difficult to store potatoes successfully if there are two
or three weeks of warm weather immediately after they
have been put into storage. In the North, cold weather
usually follows the dying of the vines so closely that it is
best to dig and store as soon as the tops die, and occasion-
ally the digging must be done while the plants are still
green in order to save the tubers from freezing. Where

230 The Potato

there is any disease in the crop, the practice of leaving the
tubers in the ground for a time after they have matured
has a distinct advantage. The infected tubers start to
rot in the ground, and when they are dug they can easily
be discarded. Otherwise they are stored with the sound
potatoes and frequently cause a great deal of rotting.

The progressive grower of potatoes will have on his
farm a breeding plot on which he is attempting to isolate
one or two superior strains of the variety which he is
growing. He ought to be constantly on the watch for
plants which show promise, and bring in the tubers pro-
duced by these for a tuber-unit test. Some time during
the growing season the farmer should go through his
commercial field and stake any plants which show quali-
ties of unusual vigor, disease-resistance, desirable habit
and so on. The product of such plants should be dug
by hand, bagged separately and records taken as to
uniformity, size, weight and so on. A consideration of
the data taken on each plant will show the grower whether
or not he should keep the tubers for further growing and
selection.

Methods of digging

The method employed in getting potatoes out of the
soil will depend a great deal on the area planted, the
type of soil and the cheapness of labor. Formerly, all
potatoes were dug by hand with spades or forks. Later
on, many growers used an ordinary plow to lift them.
Then a special type of plow, the shovel plow, was em-
ployed. Later came the various types of mechanical
diggers.

Small plantings of potatoes must always be dug by
hand, because of the high cost of the digging machines.

Harvesting the Potato 231

It is often necessary, also, to dig early potatoes by hand.
In the early varieties the skin is tender and easily in-
jured by the digging machinery. The tubers also cling
to the underground stems and frequently have to be
pulled off. A man will dig from ^ to | acres a day,
depending on the yield and type of soil.

Digging by plows is not to be recommended unless it
is a case of getting part of the crop or none. The plows
cut and otherwise injure many of the tubers, and they
cover nearly as many potatoes as they turn up. Growers
usually agree that hand-digging secures enough more
potatoes than plowing to make the extra labor well worth
while.

When the planting is relatively large, it pays the grower
to buy a good digging machine. Such machines work
quickly and are usually very satisfactory. In heavy
soils and stony soils, and in cases in which the plantings
are deep, there is a question as to their efficiency.

The type of machine commonly used in this country
has a steel nose which runs under the row and lifts potatoes
and soil onto a grating of iron rods. The soil falls through
the grating and the potatoes travel along the rods and
are dropped at the back of the machine on top of the
ground. From two to four horses are used on such a
machine. A good machine will dig from 3 to 6 acres of
potatoes a day, and will keep from 10 to 15 men busy
picking them up. A second type of digger, less com-
monly used, has a revolving frame with forks which dig
into the ground at right angles to the row. Potatoes
and soil are thrown against a screen and the soil passes
through, leaving the potatoes in a row upon the ground.

When a digging machine is used, it is sometimes neces-
sary to remove the dead vines from the rows before

232 The Potato

digging. This can be done by running a spike-toothed
harrow across the field lengthwise of the rows. It has
the added advantage of leveling off the ground where
the soil has been hilled up about the plants.

Picking and sorting

It is usually considered best to let the tubers dry on
the ground for two to six hours before picking them up.
This results in a drying and falling off of the excess dirt
and also toughens the skin and lessens its liability to in-
jury in handling. If the potatoes are left for too long a
time in the strong sunlight, they turn green and their
eating quality is injured.

Potatoes are usually picked by hand into bushel baskets
or crates (see Plate XIV). Formerly it was the practice
to empty these containers into a wagon box and to cart
the potatoes to the storage, where they were shoveled
into boxes. This method of handling usually resulted in
considerable injury to the potatoes and greatly impaired
their keeping qualities. At present, potatoes are usually
hauled from the field in two-bushel bags or in one-bushel
crates.

Alva Agee ^ recommends the use of one-bushel boxes
for carting potatoes from the field. Such boxes, he says,
should be made of basswood or some other light wood
and should be of 2688 cubic inches capacity. These boxes
are best made 12i inches deep, 13i inches wide and 16
inches long. The sides and bottom should be f inch
thick and the ends i inch thick. The length of two such
boxes is about equal to the width of an ordinary wagon
bed. With high side-boards on the wagon, these can be

1 Penn. Dept. of Agr. Bui. 105.

Wi

H

BH

!•::■) t 'tBH

H^M^H^^

H^

1

1

^Bwl^ravH^H^

1

B

WM

1

^N

l^n

1

wmM

l^^«

f^

n^^^KSnO^^HH

IBH^^S

' 41

BmEN^Sa^wII

IVRlMSirSii^SlllS

Harvesting the Potato

233

piled up in tiers and about 60 boxes put on a load. Boxes
of this description can be purchased for about 18 cents
each. Slat crates of cheaper construction can be had for
about 12 to 18 cents each. These boxes are quite dur-
able and with proper care should last 10 or 12 years.

There are now on the market machines which dig and
bag potatoes in one operation. Machines of this sort
undoubtedly save a great amount of labor, and in some

Fig. 17. One type of potato sorter.

cases will prove to be good investments. We should
remember, however, that potatoes harvested in this
manner have no chance to dry off and are therefore more
likely to rot in storage than those which have stood for
a few hours on the surface of the ground.

Where the weather will permit, it is usually advisable
to sort potatoes in the field. Various types of sorting
machines are used for this purpose (see Fig. 17 and Plate
XV). One is simply a wooden frame on runners, having
two inclined sieves of heavy wire. The largest potatoes
roll down the top sieve into a sack at the end. The
smaller potatoes fall through the upper sieve on to a finer

234 The Potato

one, and the larger of these potatoes roll down into a bag
at the end of that sieve. The very small potatoes and
pieces of dirt fall through the sorter on to the ground.
A horse can be attached to this sorter, and it can be drawn
around the field as the men pick.

Other sorters of a more complicated type are often
used in grading potatoes, but most of these are too cum-
bersome to be hauled about for field sorting.

Some potato-growers are heartily in favor of washing
potatoes after bringing them from the field. This is
done by the use of sprayers, and the potatoes are poured
on to racks to dry. Those who advocate washing claim
that it not only makes the tubers more marketable, but
that it also reduces the loss by rotting in storage. Other
growers insist that the labor of washing is not worth
while, and still others say that it is injurious to the potatoes
to wash them. Experimental evidence on these questions
is lacking.

Labor and cost of harvesting

It is difficult to make an exact estimate of the cost of
harvesting an acre of potatoes, because of the differences
in the methods, the skill of the laborers, the type of soil
and the size of the crop. Only approximate figures, there-
fore, can be given.

If the digging is done by hand, i to i an acre can be
dug by a man in a day. Fraser ^ estimates the cost of
such digging at from two to six, or even eight, cents a
bushel.

A machine will dig from 3 to 6 acres a day. If we
allow three dollars a day for the use of the team and
two dollars a day for the driver, the cost of digging an

» S. Fraser. "The Potato."

Harvesting the Potato 235

acre by machinery will vary from 87 cents to $1.67. As
this machine, digging between 3 and 6 acres a day, keeps
from 10 to 15 men busy picking, it would appear that
about 3 men are needed to pick up the potatoes on an
acre.

If the potatoes are sorted in the field, this item must be
added in figuring the cost of harvesting. The quantity
which can be sorted in one day will depend a great deal
upon the type of sorter used. From 500 to 1000 bushels
can be sorted by a machine in one day.

It is almost impossible to make an accurate estimate
of the cost of hauling from the field to the storage cellar.
The size of the wagon used and the distance of hauling
will vary greatly, and even an approximation of the cost
of this operation would probably be valueless.

The grower should always remember that the care
which he exercises in harvesting his crop will mean an
appreciable difference in its marketability. Cut and
bruised tubers bring a lower price when sold directly
from the field, and they are a complete loss when put into
storage. Poor judgment as to time and method of har-
vesting will have a detrimental effect upon yield and
upon quality. The farmer who spends time and money
to raise a good crop of potatoes should be equally careful
in getting his crop to the market or into storage in the
best possible condition.

REFERENCES
Agee, Alva.

1904. Potato Production. Kansas Agr. Report.
Agee, Alva. Penn. Dept. Agri. Bui. 105.

Bennett, E. R. The Colorado Potato Industry. Colorado Bui.
Eraser, Samuel.

1905. The Potato. N. Y. (Orange Judd Co.), pp. 143-146.

236 TJie Potato

Grubb, E. H., and Guilford, W. S.

1912. The Potato. N. Y. (Doubleday, Page & Co.), pp. 111-118.

KOHLER, A. p.

1909. Potato Experiments and Studies at University Farm.
Minn. Bui. 118.
Macoun, W. T.
The Potato and its Culture. Central Expt. Farms, Bui. 49.

CHAPTER XIII
MARKETS, MARKETING AND STORAGE

It is of interest to know the quantity of potatoes which
are marketed every year in the United States,, in order
to appreciate the importance of the marketing problems.
Such a figure, of course, can never be very accurately ob-
tained, because of the lack of statistics of various sorts
necessary in computing it. It is possible, however, to
make a calculation which is approximately correct. This
figure should be considered only as an approximation.

The following table of averages may help to give an idea
of the number of bushels of potatoes which are marketed
every year in this country :

Table XIV. — Averages for 1904-1913

Annual production 326,199,200 bu.

Quantity marketed in the fall — 50 per cent . 163,099,600 bu.

Quantity stored — 50 per cent 163,099,600 bu.

8 per cent less on stored potatoes .... 13,047,968 bu.

Quantity used for starch 5,000,000 bu.

Seed needed for next year 48,286,000 bu.

Number of farms raising potatoes 3,008,474

Potatoes consumed on farms 75,211,850 bu.

Bushels to be marketed (home grown) . . . 183,653,382 bu.

Annual imports of potatoes 2,688,148 bu.

Annual exports of potatoes 1,410,831 bu.

Excess of imports over exports 1,277,317 bu.

In figuring the seed needed, 14 bushels of potatoes were
allowed to the acre. The number of farms raising pota-
237

238 The Potato

toes is an average of figures for 1899 and 1909. An
average of five persons to a farm is considered fairly re-
liable, and each person is assumed to eat about 5 bushels of
potatoes a year.^ From these figures we can estimate the
number of bushels eaten on farms. We have then figures
from which we can compute, rather roughl}', the number of
bushels to be handled annually on the potato markets of
the United States.

From the above table, we see that nearly one-seventh of
the potato crop has to be saved for next year. About one-
twenty-fourth of the whole crop, or one-twelfth of the
quantity stored, is lost through shrinkage and rotting.
Starch manufacture and home consumption of potatoes
on the farm also take some of the crop. The quantity
left, after subtracting all of these from the crop, repre-
sents, in a rough way, the number of bushels of American-
grown potatoes to be handled on the market. If we
then balance the imports and exports, and add the excess
of imports to this figure, we have the total number of
bushels of potatoes handled in the American markets.
This is approximately 184,930,000 bushels, or 30,822 cars.^

According to statistics published by the United States
Department of Agriculture, about 50 per cent of the
potato crop has been sold by January first. A relatively
large proportion of this quantity is sold by farmers at
the time of digging, or shortly afterward. The following
table ^ gives figures for the total of 19 Northern states : —

1 The average annual consumption per capita in the United States is 3.5
bushels. The consumption is higher than this in the North and lower
in the South, where sweet potatoes are eaten in place of Irish potatoes.
Funk, in Farmers' Bui. 635, finds an average farm consumption (483
farms) of 5.7 bushels.

2 Car of 600 bushels.

» Monthly Crop Report, January 31, 1916, p. 8.

Markets, Marketing and Storage

239

^

I tv. q i> Tf< o5 iq

J

O

e

CO t>^ 05 i-i 0 06

i

6

'st^ <© Tt< 0 Tt^ TJH

<

-<

g

a

5

05 03 C^l CO 0 10 0

CL,

0

(J

gg-g^^^o

-«. 8

IN DEALEH

HANDS,

BUSHELS (0

omitted)

CO i> [>■ t^ CD r^ ■*

CO t^ 05 CO 0 iC 00

"* °l l^. ^. f^. 't. ^.

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Total
roduction,

USHELS (000

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(M 0 CO CO (M ^ 00

00 00 Tt< C^ CO ■<* 0

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02 05 05 Oi 05 Oi S

^

■"

1 1 1 1 1 1 1

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^

05 05 05 05 O) oi as

240

The Poiaio

If we average the figures for these 7 years, 1909
through 1915-1916, we have the following : —

-

CO

g

lO

K

05

VO

8

a

■-1

(5

«

<M

n

lO

g

CO

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0

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r^

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Markets, Marketing and Storage 241

It will be seen that there is an average difference in price
for a bushel on December 1st and March 1st of only 3
cents. The question which then suggests itself is "Does
it pay the farmer to store potatoes over winter ? "

When we compare the prices obtained for a bushel on
December 1st and March 1st, it would seem that the
farmer loses money by storing his potatoes. Surely the
difference of 3 cents a bushel does not begin to cover the
extra cost of storage nor the extra shrinkage and loss
through rotting. Wliy not sell all the potatoes at digging
time, or at least before January 1st? There are several
very good reasons for this.

In the first place, it would be very difficult for the dealers
to handle the whole crop of potatoes in the fall. They
lack the warehouse room and the help to take care of all
the crop at one time. Dealers would be swamped with
potatoes for a short time, and then have no more to handle
for a long time. Secondly, there is a shortage of rail-
road cars in the fall, and it would be impossible to ship the
whole crop at one time. Then, too, the farmer is pressed
for time in the fall and can use his teams to better advan-
tage than in hauling potatoes. He can better afford to
cart potatoes in the winter, when there is less to be done.

Probably the principal reason for not selling the whole
crop in the fall is the automatic lowering of prices which
follows an attempt to market too many potatoes at that
time. The dealers in potatoes will take only so many
bushels in the fall, and any sold above this quantity are
sold at a constantly decreasing figure. By storing part
of his crop, the farmer equalizes the distributing of it on
the market and gets a better net return than he would
by selling all shortly after digging.

If prices hold up in the fall, it will probably be better

242

The Potato

for the farmer to market the larger part of his crop at once
than for him to store it. Occasionally, however, the stor-
age of potatoes becomes very profitable.

In 1914, with a crop of over 400,000,000 bushels, the
price of potatoes dropped during the winter. In 1915,
when w^eather conditions were unfavorable, and the crop
suffered badly in storage, prices went up rapidly during
the winter. The winter of 1915-1916 was one in which
stored potatoes of good quality brought a high price. The
following table of estimated values a bushel, taken from
the United States Government Monthly Crop Reports,
shows the range in price a bushel during the seasons men-
tioned :

.Table XVII

Crop Reports op

Estimated Farm Values

June
August
September
October
November
January-
March .
April

50.8

71.3

56.3

87.1

50.3

74.9

48.8

64.7

60.8

52.8

70.6

49.7

94.4

50.4

97.6

47.8

Marketing the crop

The methods of marketing the potato crop may be
simple, or they may become complicated, requiring several
handlings and the services of a number of persons.

Probably the simplest method of marketing the crop is
for the farmer to sell directly to the consumer, either haul-

Markets, Marketing and Storage 243

ing the potatoes by wagon or shipping them. This can
only be done when the farmer Hves fairly close to market
and where he has good storage facilities, so that he can
sell small quantities at a time. Such a method of market-
ing is usually highly satisfactory, for it gives the pro-
ducer the highest possible share of the profits and the
consumer the lowest retail price. The farmer may also
sell locally to retail grocers, thus eliminating the services
of one to three or four middlemen. Obviously, only a
very small proportion of the total crop can be marketed
in these ways. Such methods of marketing necessitate
much labor, and require good storage accommodations
and an intimate knowledge of markets.

Marketing through local dealers

It is usually necessary for the farmer to sell his potatoes
to a local dealer, who in turn stores some of them and sends
the remainder to the commission men in the larger cities.
These dealers are familiar with the requirements of the
different markets and are usually able to sell the potatoes
to a better advantage than can the farmer.

The local dealers or buyers are to be found in nearly
all towns where large quantities of potatoes are being
brought in by the farmers. They usually sort and bag the
potatoes and load them in cars for shipping. Occasionally
a farmer or a small group of farmers will load and ship a
car, but the bulk of the crop is handled by local buyers.
These buyers, according to Taylor, may be of several sorts.
They may be agents of large potato companies in the cities,
or they many be independent buyers who combine other
lines of business with that of potato-buying, or they may
be agents of farmers' warehouses or cooperative associa-

244 The Potato

tions. The large potato companies usually have from one
to several buyers in the more important potato-growing
sections, to purchase from the farmers and ship the pota-
toes, at their direction, to the best markets. These buyers
handle potatoes at 4 to 8 cents a bushel. The agents of
the farmers' warehouses, who are dealing in other prod-
uce as well and have lower running expenses, are able to
handle a bushel for about 3 cents.

In many of the large cities there are companies which
handle only potatoes. These companies get potatoes
from the farmers through the local buyers, and then
by means of telegraph and telephone ascertain the
best markets and direct the shipment of the cars to
them. They are handling great quantities of potatoes
and can afford to spend large sums in order to get their
goods to the best market. Companies of this sort
often pay telephone charges of over one thousand
dollars a month.

Where farmers can be persuaded to cooperate and to
place faith in the organization and in its agents, the co-
operative method of selling potatoes has proved very satis-
factory. Such organizations have agents in the small
towns near which the members live. These agents receive
potatoes from the farmers, and ship them at the direction
of the manager of the company. These managers have to
compete with the large potato companies, and are often
at a disadvantage in getting information as to markets.
Farmers' companies should either be in touch with large
distributors or arrange with some company for "buying
information."

Local dealers usually find it necessary to sort and clean
the potatoes brought to them, since growers seldom
make a practice of sorting carefully. Potatoes are sorted,

Markets, Marketing and Storage 245

bagged or put in barrels for shipment. Occasionally a
farmer will insist that his potatoes be sold without being
sorted before shipment. These are sorted in the city
and the culls are thrown out. The grower gets nothing
for the culls and he must pay the expense of freight on
them.

Grading

Potatoes are poorly graded, and for this reason the cost
of marketing is higher than in the case of goods which are
classified by grades. Potatoes of several varieties are usu-
ally raised in the same section, and it is often hard to fill a
car with only one variety. Experienced potato-shippers
sort and grade carefully and get a higher price a bushel
than is ordinarily paid. One produce exchange in Vir-
ginia has so standardized its potatoes that wholesalers
order by wire, without seeing the goods. Sorting and grad-
ing on the farm, or at least before loading on the cars, not
only makes it possible to secure a higher price for the pota-
toes, but reduces the cost of marketing as well. The
farmer ultimately pays the cost of grading, and often after
he has paid the freight on as much as a ton of dirt and
culls.

Packages

Early potatoes are usually shipped in three-bushel
barrels, covered with canvas, or in bushel boxes. The
barrels, with covers, cost about 20 cents apiece. Bushel
boxes — 13 X 16 X 13 inches deep — cost about $30
a hundred. Seed potatoes are frequently shipped in
double-headed barrels of 165 pounds capacity. These
cost about 30 cents each.

246 The Potato

Late potatoes are usually shipped in burlap sacks,
holding two bushels. Sometimes flour barrels are used,
and occasionally the potatoes are shipped in bulk in car-
load lots.

Shi'p'ping

When potatoes are shipped in bulk, it is necessary to
line the whole car with lumber. If the potatoes are
bagged, it is not necessary to line the car, but a false floor
must be put in. It costs the local dealer ordinarily a
little over $30 to line a car.

In the winter, it is necessary to heat the cars, and a man
has to be sent along with the car to regulate the heat.
Here again the larger dealer has the advantage, since he
can ship several cars at once and reduce the cost of heating.

Water transportation plays an important part in the
shipment of early potatoes from the southern states to
the larger cities of the North.

Most of our potatoes are raised near the larger towns and
cities, and the distances of shipment are relatively small,
Chicago receives potatoes from Michigan, Illinois, and
Wisconsin, a large part of her supply coming from the last
state mentioned. New York and Philadelphia get pota-
toes from New York state, New England, Long Island,
New Jersey and the southern Atlantic states. Only a
few states raise potatoes for interstate shipment. Taylor
says that three-fourths of the potatoes grown are consumed
in the states which raised them. Maine raises 25 per cent
of the potatoes for interstate shipment, Michigan 24 per
cent, Wisconsin 20 per cent, Minnesota 16 per cent and
Colorado 8 per cent.

After reaching the city in which they are to be marketed,
the potatoes may take any one of several courses to the

Markets, Marketing and Storage 247

consumer. Very often they pass through the hands of a
commission man, and frequently they go directly to the
wholesaler. In the larger cities, a considerable part of
the crop goes to the commission man, who, in turn, dis-
tributes it among the jobbers or wholesalers. The com-
mission man may employ a number of salesmen, or he may
depend upon an expert potato broker to bring in orders
from the wholesalers. Often goods are shipped around
the commission men to the brokers, and thence to the
wholesalers.

The diagram (Fig. 18) may help to make clear the
methods of marketing potatoes. Perhaps it will seem that
there are too many middlemen concerned in the market-
ing of this crop. In many cases there are. We must not
lose sight of certain conditions of potato marketing, how-
ever. The retailer sells in small quantities, and he has no
room to store more than a small supply of potatoes. He
must needs depend upon the wholesaler for his supply.
The wholesaler in turn has to cater to a fairly definite de-
mand from the retailer. He cannot take ever^^-thing which
is sent to him by the farmer, but must have access to the
supplies of the commission man in order to get the desired
variety and grade. So we have the potatoes coming to the
large dealer or commission man, who sells in small lots to
the wholesalers, and the wholesalers divide the product
into still smaller parcels and sell to the retailer. The
lack of proper grading, the bulkiness of the goods, and the
demand for small quantities at a time, tend to make
necessary the services of several classes of dealers in the
process of marketing potatoes.

There is no chance to gamble on potatoes, as on wheat
and certain other crops, since there are no exchanges where
the traders can come together. The potato market is

248

The Potato

lO

Fig. 18. Diagram illustrating interrelationships of producer, middle-
men and consumer of potatoes. 1. Farmer. 2. Agent of farmer.s' ware-
house or of cooperative company. 3. Independent local buyer. 4. Local
buyer for large potato company. 5. Wholesaler. 6. Commission man.
7. Broker. 8 and 9. Retailer. 10. Consumer.

Markets, Marketing and Storage 249

not very highly organized, and exact market information
is very difficult to obtain.

Early and late potatoes

The earliest potatoes to reach the northern markets
come from the Bermudas and Texas in January and
February. Florida and other southern states add to the
supply a little later, and about the first of June a large
quantity begins to come in from Virginia and other south
central states.

Early potatoes from southern New Jersey enter the
market about July twentieth and those from the northern
part of the state and from Long Island about ten days to
two weeks later. Early potatoes from New York and
Maine are usually marketed between the first and fifteenth
of September. The southern potatoes have little effect
upon the price paid for northern-grown potatoes, providing
they are out of the market by August. If southern pota-
toes are late in reaching the northern markets, potatoes from
New Jersey, Long Island and Pennsylvania are sold in com-
petition with them and consequently bring a lower price.

The main crop of late potatoes begins to come into the
market early in October. From then on, the extent of
the sales and the price for a bushel depend upon many
factors. Chief among these is the supply of potatoes then
upon the market.

Markets

The larger potato markets of the United States are New
York, Chicago, Minneapolis, St. Louis, Cincinnati, Den-
ver, San Francisco and Boston. Chicago handles annually
about 24,000 cars, or over 60 cars a day. Each of these

250 The Potato

cities draws upon several states for its supply of potatoes.
The eastern cities often get European potatoes in years of a
poor crop, and occasionally these potatoes get as far west
as Chicago.

Range and 'prices

There are few crops which fluctuate as much in value
as the potato. In a single season the prices may show a
range of as much as 70 or 80 cents a bushel. The highest
prices are usually obtained in the late winter and early
spring just as the early potatoes come on to the market.
This value is not likely to fluctuate a great deal while
early potatoes are abundant, but it drops off rather sud-
denly as soon as the late crop comes in. Usually the price
for a bushel remains fairly constant through the winter,
though it may fluctuate a little either way. Later in the
winter it is likely to rise somewhat or to drop off slightly.
These fluctuations in price are due largely to a change in
the relation of supply to demand.

In 1899, the farm price was as low as 22 cents in Iowa
and as high as $1.10 in Arizona, with an average price the
country over of 36 cents. In 1915, the prices ranged from
35 cents in South Dakota to $1.15 in Florida, with an aver-
age of 61.6 cents. These Avide fluctuations in price illus-
trate the effect of supply and demand upon the value a
bushel. The average farm price a bushel for the years
1906-1910 was 60.4 cents. The highest average farm
price on December first, since 1866, was 79.9 cents in 1911,
and the lowest in the same period was 26.6 cents in 1895.
In recent years, Arizona has had the highest value to the
acre, averaging $127.68 for the 5 years from 1910-1914.
The lowest value to the acre during the same period was
$42.43 in Missouri.

Markets, Marketing and Storage

251

The following table ^ gives the prices received for a
bushel by the Burlington County Farmers' Exchange of
New Jersey, for four years :

Table XVIII.

Seasonal Variation in Farm Price for a
Bushel

Period

1911

1912

1913

1914

July 12 . .

$1.25-11.35

July 15-20 .

1.25- 1.30

|.65-$.80

S.60-$.80

July 25-30

1.05- 1.20

.68- .83

.65- .68

$.60-1.80

Aug. 1-10 .

1.05- 1.25

.62- .80

.65- .73

.53- .70

Aug. 20-31

.80- 1.00

.55- .60

.60- .68

.50- .58

Sept. 1-15

.48- .50

.60- .68

.52- .55

Sept. 15-21 .

.75- .80

A survey of the figures published by the United States
Department of Agriculture shows that the price paid for a
bushel on December 1st tends to vary immensely with the
size of the crop :

Table XIX

Year

Production

Farm Pi^ice — in Cents

(000 omitted)

December 1st

1904

332,830

45.3

1905

260,740

61.7

1906

308,040

51.1

1907

298,260

61.8

1908

278,990

70.6

1909

289,190

54.1

1910

349,030

55.7

1911

292,740

79.9

1912

420,650

50.5

1913

331,530

68.7

1914

405,920

48.9

1 N. J. Extension Bui., Vol. 5, 1915.

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Fig. 19. Average yields of potatoes to the acre, a, 50 bushels ; h,
60 bushels ; c, 70 bushels ; d, 80 bushels ; c, 90 bushels ; /, 100 bushels ;
0, 110 bushels.

252

Markets, Marketing and Storage 253

The graph in Figs. 19 and 20 illustrates this same rela-
tion between production to the acre and value a bushel.

If the consumer of potatoes examines a list of farm prices,
as published by the United States Department of Agricul-
ture, he is usually surprised to find that he is paying at
least double what is paid the farmer for a bushel of potatoes.

Under present conditions the cost of marketing potatoes
is relatively high. It could be cut down appreciably if
farmers would codperate in marketing and would grade
their stock carefully. Taylor publishes statements from
a potato merchant to show the distribution of the cost of
marketing a bushel.

The local buyer pays, on the average, three cents a
bushel for the labor of handling the potatoes. Bags cost
about 5 cents, and the dealer asks a profit of about 2
cents a bushel.

The freight charges vary a great deal with the distance
of shipment. Taylor says that it costs about 8 to 8i
cents a bushel to ship from Wisconsin to Chicago. To
the freight must be added the cost of lining and firing the
car, when the potatoes are shipped in the winter. This
will cost about 2 cents a bushel. It costs the small
shipper from $7 to $10 a car for heating, while the large
dealer will send through a string of 5 to 20 cars for about
$1.50 each. We must count on a certain loss in transit
through frosting and rotting. Then, too, under present
methods of grading and marketing there is almost always
a loss of 20 to 40 bushels of culls to a car, and occasionally
as high as 100 to 150 bushels. These potatoes are a total
loss to the buyer, and the freight paid on them is also lost.
As a result of this loss on culls, the price for a bushel rises
somewhat.

The larger distributor or commission man usually nets

254

The Potato

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Fig. 20. Average prices of potatoes by the bushel, a, 30 cents ; h,
40 cents ; c, 50 cents ; d, 60 cents ; e, 70 cents ; /, 80 cents ; g, 90 cents.

Marhets, Marketing and Storage 255

about 2 cents a bushel profit in addition to his expenses
of li to 2 cents a bushel.

The wholesale dealer incurs an expense of 5 to 7 cents a
bushel in draying to his warehouse and later distributing
to the retailer. He must also make a profit on each bushel
handled.

There is also the retailer, whose profit must necessarily
be high. This last profit varies from 15 to 30 cents.

A summary of all expenses incidental to marketing the
crop shows a cost of 39 to 70 cents a bushel :

Table XX

Retailer 15-30 cents

Wholesaler 5-10 cents

Transportation 8-10 cents

Larger distributor 3-4 cents

Burlap sacks and car linings 3-5 cents

Local dealer 5-11 cents

39-70 cents

The cost of marketing varies greatly, depending on a
number of factors. The distance to market affects freight
charges very directly. The time of year when the potatoes
are shipped has a bearing on loss in transit and cost of heat-
ing the cars. Costs are markedly influenced also by the
number of middlemen helping in the sale of the potatoes.
Each one must make a profit. There is a lack of definite
standards of quality in potatoes, and consequently at
each exchange of goods there is keen bargaining to buy
low and sell high. The retailers' cost of marketing de-
pends largely upon the quantities purchased at one time
by the consumer, and the cost of delivering and of main-
tenance.

It is obvious that a lowering of the cost of marketing will
be profitable both to the producer and the consumer. The

256 The Potato

latter will be able to buy potatoes for less a bushel, and the
former will receive a larger share of the retail price than
before. The farmer should aim to cut down the expense
of growing and hauling to the local buyer. He can lower
freight charges by sorting carefully and thereby not pay-
ing freight on culls. By grading his stock and market-
ing the best, he can raise the price which he receives a
bushel. Perhaps the most effective means of lowering the
cost of marketing is for the farmers to organize coopera-
tive selling companies. Such organizations have most
of the advantages of the larger potato companies, in the
way of decreased cost of hauling and better marketing
information. In some cases the number of middlemen
can be cut down. We must remember, however, that the
potato is a bulky crop of a perishable nature and therefore
must be carefully held in storage while awaiting shipment.
This necessitates, for part of the crop at least, the services
of the large distributor who can hold the goods safely
until called for by the wholesalers. There must be re-
tailers who can sell potatoes in small lots to the consumer.
Perhaps one or even two of these steps might be dropped
out occasionally, and the expense of handling several times
be eliminated.

There are many factors which determine the price of
potatoes. A careful study of these and skill in forecast-
ing as accurately as possible the probable price which
potatoes will bring from the time they are stored until the
last of them are sold late in the spring will determine
whether it will pay to store them or not.

The farm price of potatoes at digging time is usually
very low. Most growers do not have storage facilities
and must put their product on the market in the fall.
This increases the supply and lowers the price.

Markets, Marketing and Storage 257

The principal factor which will determine the advisa-
bility of storage is the probable winter and spring price ;
others are the soundness of the tubers at digging time ;
relative ease of getting them on the market in the winter ;
their use for table stock or seed purposes and so forth.

Ordinarily a low-price season, resulting from overpro-
duction, will be followed by a season of high prices. The
grower should be carefully informed concerning the
acreage of the whole county during the growing season and
the reported condition of the crop from different sections.
An extensive acreage and a favorable season results in
low prices.

The average consumption per capita in the United
States is from 3§ to 4 bushels. If the acreage and weather
conditions over the whole country are likely to produce
a crop of over 400 million bushels, low prices may be
looked for. The population of the United States is ap-
proximately 100 millions. At the rate of consumption of
3| bushels for each person, the total consumption will be
350 million bushels.

The United States Department of Agriculture issues a
crop reporter each month which gives the condition of the
potato and other crops from all over the country. It is
issued free to all and arrives about the 20th of each month.

The amount of importation of potatoes into the United
States is regulated by the price here and elsewhere, which is
in turn largely determined by the quantity of production.
The protective tariff on potatoes is 10 cents a bushel.

The basis for storage must take into account American
production and the probable price and the foreign pro-
duction and price. When home prices reach a high level,
foreign potatoes are sure to become a price-determining
factor.

258

The Potato

It is obvious that all seed stock must be stored either
by the grower, who may save his own seed, or by some large
concern, who may store it for sale to growers in the spring
(see Fig. 21). Seed stock should, perhaps, be stored more
carefully than potatoes for eating purposes. Complete
dormancy is necessary if the seed is to produce a good
crop. If storage is not carried out properly, the tubers

Fig. 21. Potato storage house.

become shriveled and are likely to produce long, weak
sprouts, which greatly weakens them. Many growers
follow the practice of storing stock in bags and turning
the bags every week in the spring to break off the sprouts
and prevent rapid deterioration. This practice when fea-
sible seems to be very successful.

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CHAPTER XIV
USES OF THE POTATO

The potato is one of the most important vegetable
foods. Its rise in popularity since its introduction into
Europe has been very rapid. At first the tubers were
regarded as poisonous, and only a few of the more ven-
turesome dared to eat them. When these men found the
potato to be edible, the people of France and Germany
began to plant it as a reserve food in case other crops
failed. By 1770 it had become a common field crop in
Europe. These potatoes, however, were usually small
in size and of poor quality, and for this reason they were
used principally as a food for animals. The possibilities
of improving the crop were soon learned, and by 1840 it
was being widely used as a substitute for the cereals and
other starchy foods. In 1900 it was estimated that the
potato furnishes about ^ of the total food consumed in
the United States.

Although it is primarily a food crop, the potato has a
great variety of uses (see Plate XVI). For a long time it
was the chief source of commercial starch, and although
cornstarch is now preferred, the starch of the potato
is still used in large quantities to make sizing for paper
and textiles. Another important use for potatoes is in
the manufacture of industrial alcohol. This industry is
almost unknown in this country, but in Europe it has
259

260

The Potato

attained large proportions. Potato flour, glucose, sirup,
mucilage and a number of tinctures are also made from
potatoes. In Europe the small potatoes and culls are
used to feed stock, and the slops from the manufacture
of alcohol are carted away daily for this purpose.

USE FOR HUMAN FOOD

So accustomed have we become to the potato that it
is difficult to imagine our tables without it. It furnishes
us daily with an abundant supply of nutrients at a rela-
tively low price. Primarily it is a starchy food, but it
also contains some protein and a little mineral matter,

and it adds bulk
to the food eaten.
It is said that the
potato represents
3.9 per cent of the
total cost of food,
and furnishes 5.3

Fig. 22. Composition of the potato, a, fat; per CCUt of the heat
?, crude fiber and other carbohydrates exclusive ^^lories needed by
of starch ; c, protein ; a, ash. •'

the body. As the
potato is somewhat deficient in protein and fats, it cannot
be used exclusively in the diet, but must be combined
with lean meat, legumes, eggs or other protein-supplying
foods, and with cream, butter or other fatty substances.
Not only does the potato furnish considerable nutri-
ment, but it supplies it in an easily digestible form. The
starch in potatoes is much more readily digested than
the starch of cereals or other starch-producing foods. In
Germany a gruel made from the pulp of baked potatoes
is used to feed infants and invalids.

Uses of the Potato 261

It is said that about 20 per cent of the tuber is waste.
As this percentage is mostly skin and that part of the
cortical layer removed with it, the percentage will vary
with the size of the potato, the shape and the care used
in feeding it. About 62 per cent of the whole tuber is
water, and about 78 per cent of the edible portion is
water. Carbohydrates form about 18 per cent of the
peeled tuber. About 2 per cent is protein and 1 per cent
ash. The fat content is rather low, being only 0.1 per
cent (see Fig. 22). A large proportion of the protein
and minerals is contained in the outer layers of the potato,
and frequently much of this is lost in careless peeling.

Quality lohen cooked

The requirements for quality in a cooked potato vary,
depending on the personal taste of the user and on the
particular way in which the tubers are to be cooked. In
America a mealy, white-centered potato is usually pre-
ferred for boiling, steaming and baking. Europeans fre-
quently prefer a less starchy potato, which means one
with a higher percentage of protein. Such potatoes are
richer in flavor and of better substance than the mealy
ones. In some sections of Europe a mealy potato is in
demand for boiling, and a waxy potato for frying and for
salads. If Americans were to discriminate in favor of cer-
tain textures of flesh for special purposes, varieties meet-
ing the requirements would undoubtedly be developed.

There are many factors influencing the quality of a
potato when cooked and its value as a food. Undoubtedly
the nature of the soil in which the tubers are formed has
some effect upon these characters, but, so far, no definite
relation has been worked out. It is also true that disease

262

The Potato

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Uses of the Potato • 263

and seasonal conditions affect quality. In addition to
these factors, there are chemical composition, degree of
maturity, conditions of storage and methods of prepara-
tion for the table, all having an important bearing on
quality and food value.

There are three textures of flesh in the cooked potato
as determined by the chemical composition : soggy,
waxy and mealy. The soggy potato is usually rather
low in starch and relatively high in protein. In potatoes
of this type, when the starch grains are heated they swell
up, but there are not enough of them to burst the cell-
walls in the tuber and give the starchy and mealy condi-
tion so often desired. The tuber more easily absorbs
water and becomes wet and soggy at the center. The
protein also tends to coagulate and make the flesh heavier
than it is in the mealy potato.

In potatoes of a waxy texture, there is a greater propor-
tion of starch to protein. The protein serves as a frame-
work which prevents the starch from forming flaky masses
and holds the potato together better. Such potatoes are
desired for salads and for garnisliing meat dishes.

In the mealy potato, the cells are packed with starch
grains. These expand with the heat of cooking and tear
apart the cell-walls, making the center of the tuber a
mass of flaky starch. If the starch content is too high,
the tubers will fall to pieces in cooking. The optimum
starch content is about 20 per cent of the peeled tuber.

Potatoes are of the best quality when they have ma-
tured fully and have been freshly dug from the soil. At
this time the starch has been fully developed. Immature
potatoes are usually high in protein, and they frequently
contain acids and sugars which affect their flavor. The
albuminoids which are frequently found in immature

264 The Potato

tubers gelatinize on cooking and make the flesh moist
and soggy. Potatoes with a netted skin and crisp flesh
are most Hkely to be mealy when cooked.

No matter how carefully potatoes are stored, there are
changes in composition taking place all the time, which
affect the quality. The tuber, like an apple, is a living
thing, and life processes are going on in it, though to be
sure they are slow\ As the winter proceeds, enzymes
begin to work upon the starch and sugars and to break
them down. Water and carbon dioxide are given off as
a result. This causes a loss of starch and a shrinkage of
the tuber. The sugars developed usually give the potato
a sweeter taste than is found in the freshly dug tubers.
Towards spring the potatoes begin to sprout, and of
course at this time the chemical changes are rapid. There
is a rapid loss of mealiness accompanying the sprouting.

The method of cooking has some effect upon quality
and food value, but it is usually because of a modification
of the texture or the combination of fats and other sub-
stances with the potato in the process of cooking. Boiled
potatoes are most likely to lose in food value during cook-
ing. This loss can be minimized, however, by cooking
with the skins on. Baked potatoes lose very little, either
in nutrients or in quality, when cooked. They are
usually more mealy than potatoes which have been boiled
or steamed. ]\Iashed potatoes are usually seasoned with
milk or cream and butter. This makes them higher in fat
than when they are boiled or baked. Potatoes fried in
fat are richest in food nutrients. The water is largely
extracted and much fat is absorbed. Where possible, it
is best to cook potatoes with their skins on. Experi-
mental studies have shown that when potatoes are boiled
in the skins, practically no starch is lost and only a

Uses of the Potato 265

small amount of the protein and ash or mineral matter.
Potatoes which are peeled and soaked in water before
cooking often lose as high as 7 per cent of their nutrients.

USE FOR STARCH

The principal article of manufacture from potatoes is
starch. Until cornstarch supplanted it, potato starch
was largely used in cooking. Now it is mainly employed
for making sizing for paper and textiles, and for other
technical purposes. Potato starch has also sometimes
been used as an adulterant of fine flours and starches.

The total annual production of starch from potatoes in
the United States is about 15,500 tons, of which 6000
tons are produced in the county of Aroostook, Maine.
The soil of this county is unusually well adapted to potato
growing.

Unless the price of marketable potatoes is very low,
only the small injured or refuse potatoes are sold to the
starch factory. Whenever the price of good merchant-
able potatoes is above 50 cents a barrel, the farmers find
it more profitable to sell directly to the market.

Process of starch mamifacture

The potatoes which are kept in a storehouse are carried,
after weighing, to a revolving washer about 12 feet long
and 18 to 24 inches in diameter. They are pushed to
the comminutor through the washer bj^ means of a per-
forated spiral or by arms attached to a revolving axle.
A stream of water flowing in the opposite direction to
that of the motion of the potatoes secures the final w^ash-
ing with clean water. By the time the potatoes have

266

The Potato

reached the comminiitor they are practically free from
dirt. A diagram of this machine is shown in Fig. 23.

The rasping machine consists of a cjdinder about 30
inches in diameter and 30 inches long. It is made of

Fig. 23. Machine for wasliiug potatoes.

wood and is covered with pieces of sheet iron punched
full of holes about | of an inch in diameter. These holes
have the rough edges outward. This rasping machine or
comminutor is shown in Fiiis. 24, 25.

FiQ. 24. Rasping cylinder or comminutor.

The rate of revolution of the cylinder is about 600 a
minute. It revolves as near a brace of hardwood as pos-
sible, and the potato, being stopped from passing by the
brace, is reduced to a fine pulp by the rapidly revolving
drum.

Uses of the Potato

267

From the rasper the pulp falls on to a starch separator,
the bottom of which is of fine wire gauze having 30 meshes
to the inch, the openings being -^ of an inch in diameter.
The separator is slightly inclined, so that the shaking

Fig. 25. Rasping machine (cross section).

process gradually moves the pulp toward the lower end.
This separator is of the same width as the rasps, namely,
about 36 inches, and is about 12 feet long.

During the progress of the pulp along the separator,

268

The Potato

jets of water are thrown upon it from pipes arranged
above. This water detaches the starch granules from the
pulp, and the granules, being small, are carried through
the meshes of the gauze, while the pulp is left on the
screen and ejected finally at the lower end.

The starch which

is carried through
by the water falls
in large tanks, vary-
ing in size from 20
to 40 feet in length
and width and from
6 to 8 feet in depth.
The starch settles
to the bottom very
quickly and the red-
dish-colored super-
natant water can
be drawn off. In a
few hours the starch
has all settled in a
hard, compact mass
at the bottom of
the tank. The proportion of starch and water is such
that 4 inches of starch is overlaid with about 6 feet of
water.

The crude starch obtained in this tank is then thrown
into another tank of a similar size which is fitted with a
revolving stirrer; water is added in large quantities at
the same time and the starch is beaten into a cream and
again allowed to settle. The interior view of such a tank
can be seen in Fig. 26. This process washes the starch
and removes the larger portion of impurities.

P^iG. 26. Starch washer (interior view).

Uses of the Potato 269

In the second settling the pure starch is first to go to
the bottom, and when the water is drawn off it is found to
be covered with a thin layer of starch mixed with various
forms of impurities. This layer is removed separately,
and the pure starch underneath is ready for the drying
tables.

The layer of dirty starch removed as above indicated
is given a second washing and if necessary a third, until
the starch is thoroughly cleaned.

The most modern way of drying is to have the starch
stream out on shelves made up of slats through which
the dried starch can fall to the shelf below. The drying
kiln is heated by steam pipes running along the bottom
underneath the shelves. The entrance for air is so
arranged that it will come in over the pipes and thus
become dried.

The starch is first placed upon the upper floors on these
wooden slats which have openings of about | inch. This
is the coolest part of the kiln, so that the starch wdiich is
most moist is subjected to the least amount of heat. It
is not safe to submit very wet starch to a high tempera-
ture, for there would be danger of converting it into a
paste and rendering it unfit for market. When the starch
is partially dried, it is raked over the grated floor and the
particles which are dry enough to be easily detached fall
through and strike similar grates below. This raking
process continues until the starch in a fine powder form
reaches the lower fioor in a state of dehydration suitable
for barreling. The dried vstarch is finally raked into a
trough running alongside of the lower floor of the kiln,
and from there it is placed in the barrels.

It requires about 12 hours to complete the drying
when the most efficient kilns are used, so that the kilns

270 The Potato

are oharged twice a day. The size of the kilns is, of
course, proportionate to the capacity of the house. For
a house using 1200 barrels of potatoes a day the kilns
are about 40 feet long and 30 feet wide, and the drying
shelves are about 15 feet in height.

After the starch is thoroughly dried, it is placed in
heaps in order that the moisture may be evenly dis-
tributed throughout the mass. It is evident from the
method of drying that some parts of the starch come from
the kilns drier than others, as this banking or heaping of
the starch is very essential in order to get uniformity of
moisture. After the mass of starch has become uniform
in its content of moisture, it is placed in barrels and is
then ready for transportation.

of potato starch

Starch and its by-products have many uses in the
technical and industrial world. It possesses peculiar
properties rendering it especially valuable for use in
print works. The makers of prints are even willing to
pay a considerable increase in price for potato starch
over that which they would have to pay for starch from
Indian corn.

In the textile industries, it has come to be used exten-
sively and in many ways.

It is used in the manufacture of cotton, woolen, linen
and silk goods for three distinct purposes : as a sizing
for the warp yarn before it is woven ; for finishing goods
after they have been woven ; in the form of dextrin or
roasted starch, as a thickener, or vehicle for applying
colors to the fabric.

In Europe, especially in England, large quantities of

Uses of the Potato 271

potato starch are used for the manufacture of dextrin or
British gum, as it is called ; in which form it is used for
various kinds of mucilage, as, for instance, that applied to
postage and other stamps. The manufacture of dextrin
of this kind is an important branch of the industries con-
nected with starch.

The pomace or residue which is left in the manufacture
of starch from potatoes has been used to some extent as
a food starch, and its use as a food will be discussed later
under food for stock.

USE FOR INDUSTRIAL ALCOHOL

Next to starch, industrial alcohol is the most important
product of potatoes. The potato is one source of such
alcohol, and in Europe, especially in Germany, is the chief
source. As yet this sort of production in connection
with potato-growing has not gained a foothold in the
United States. But a brief survey of the wide extent of
the practice in Germany may throw some light upon its
possibilities.

In Germany, with the extension of the cultivation of
the potato, which gives a larger starch yield to the acre
than the cereals, the distillation of alcohol has become
largely an agricultural industry. The use in Germany
of potatoes for making alcohol has steadily increased
from 1,915,800 pounds in 1855 to 4,706,820,000 pounds
in 1905. The consumption of potatoes has increased,
therefore, nearly 2500-fold during 50 years. In this
connection it must be remembered that the starch con-
tent of potatoes has also been increased. The best
indication of the growth of the potato alcohol industry
is from the output of the finished product.

272 The Potato

1855 32,757,700 gallons absolute alcohol

1860 42,003,825 gallons absolute alcohol

1865 52,570,825 gallons absolute alcohol

1906 . exceeded 115,444,445 gallons absolute alcohol

Distillation is, therefore, a very important and exten-
sive agricultural industry in Germany. There the potato
is the principal source of alcohol, and the production of
spirits from other substances is insignificant in comparison
with that from potatoes.

The agricultural significance of the development of the
potato industry as worked out in Germany is manifold.

1 . All the ingredients taken from the soil by the potato
are returned to the soil.

2. The mash, which is the product obtained after the
starch has been converted into alcohol and the latter has
been removed by distillation, is a valuable feed for cattle.
This enables the farmer to maintain a large number of
cattle, and they in turn provide the manure so necessary
for the light soil.

3. The introduction of a cultivated crop into the rota-
tion has been of the greatest benefit, because it has made
possible larger yields of grain.

4. It has enabled the farmer to convert the unstable
crop, especially of those varieties of poor keeping quali-
ties, into a stable product, alcohol, which may be held as
surplus stock for several years.

As was shown above, potatoes have been used in other
countries as a source of cheap alcohol, and the possibili-
ties of its becoming a profitable enterprise in America are
very promising ; for conditions in this country indicate
that large quantities of potato culls with the necessary
starch content are available for this purpose at a price

Uses of the Potato 273

which would permit of the profitable manufacture of
alcohol therefrom. Experimental work at the United
States distillery has shown that the potato can be eco-
nomically handled in manufacturing alcohol, and the
farmer can convert frosted or inferior grades of potatoes
into a source of revenue. It also furnishes in the resi-
due, or slop, a feed for stock. In recent years, many
persons have become so much interested in this industry
that it seems advisable to give a somewhat thorough
discussion of the methods of manufacturing alcohol from
potatoes.

The alcohol from potatoes is a result of the action of
malt or acids on the starch, which is turned into sugar
and then fermented to give this final product. The so-
called "denatured alcohol" is prepared by the addition
of such ingredients as will make the alcohol unfit for
drinking purposes. This alcohol is used extensively in
the manufacture of varnish, explosives, chemicals and
many other commercial substances. It may also be used
in various household appliances, both for lighting and
heating purposes, and with much more safety than either
kerosene or gasoline.

This discussion is limited to the methods which can be
used upon a farm, or by a farm community, in a small
distillery handled by the farmer himself. The potatoes
should of course have enough starch to be worth using
for this purpose. From experiments it has been deter-
mined that there should not be less than 6 per cent of
sugar or starch before the materials can be considered
suitable for the profitable manufacture of alcohol.

274 The Potato

The manufacture of alcohol from potatoes

The first essential in manufacturing alcohol from potatoes is that
the distillery should be centrally located in a potato-raising country ;
and seconflly, the railroad facilities should be such tliat delivery of raw
materials and feed, and the marketing of the finished product, can
be done at a minimum expense. An abundant supply of cold soft
water is of almost equal importance. It is desirable that the plant
be near a creek or stream from wliich water may be obtained and into
which it may be drained after serving its purpose in the distillery.

As the distillery cannot be run tliroughout the entire year, the
machinery should be simple, practical and economical. Advantage
should be taken of the laws of gravity to save pumping whenever
possible. This can be done by arranging the apparatus so that each
operation will be on a lower level than the preceding one; thus
by elevating the raw material to a height suitable for the first opera-
tion, it will flow from one apparatus to another by its own weight.
All machinery requiring steam should be placed close to the boiler
so as to avoid condensation caused by long pipe connections. Ex-
haust steam from the engines and pimips should be used in the dis-
tillery apparatus and the hot water from the condenser should be
utilized as feed water for the boiler. Each piece of apparatus should
have a capacity equal to the exact amount of work it is expected to
do, the only exception to this being the boiler, upon the efficiency of
which depends the proper working of each piece of apparatus. The
boiler should be of a slightly larger capacity than is actually required.

This following data on the cost of a distillery are of a supposed
plant which has a capacity for handling 8000 poimds of potatoes
in one working day of 10 hours. The building is one story high,
with a ground space of 1000 square feet. The walls are constructed
of any available material. In many cases farm buildings, such as
barns and the like, could be used. Such a building will not cost
more than $1500. Total cost of machinery and equipment not
inclusive of motor power is about $9000. One 75-horsepower
boiler and a 25-horsepower engine will be required and will cost about
S1500. This would make a total investment of about $12,000.

A day's expenses will include the cost of potatoes, barley, fuel
and labor. Cull potatoes can be delivered at a distillery in some
potato-growing districts at 2.5 cents for 100 pounds. At this rate
the raw material for a day's run of 8000 pounds will cost $20. To

Uses of the Potato 275

convert the starch of the potatoes into sugar, there will be needed
the green malt yielded by 120 pounds of barley, which at 70 cents a
bushel will cost $1.75.

The cost of fuel varies with the fireman, but with proper care and
efficient use one ton at $4 should be enough for a day's operation.
Three men will be required, consisting of a fireman and two laboi'ers.
This will total up to about $33 for daily operating expenses.

Operating a distillery. — The first process is to wash and then
cool the potatoes so that the starch present can be thoroughly
converted into sugar by the action of the malt. The potatoes are
placed in a vacuum cooker and steamed until they are thoroughly
cooked. The steam pressiu-e in the cooker is allowed to rise to 50 or
60 pounds. The entire time required for warming the potatoes and
reaching the maximum pressure should be about one hour. The
potatoes are stirred and the pressure held for about ten more minutes
to insure a good cooking of the starch. Then the temperature of
the cooked potatoes is allowed to fall to 212° F. The temperature
of the cooked potatoes is further reduced by means of the vacuimi
pump to 140-145 F.° at which point the malt necessary to change
the starch to sugar is added. About 2 pounds of malt is added for
each 100 jwunds of potatoes mashed. The green malt is crushed
between rolls, while dried malt is ground in a mill before using.
About fifteen minutes before the mash in the cooker is ready for
malting, the malt already ground is mixed with water at the rate of
1 gallon of water to 2.5 pounds of dried malt, or f gallon of water to
same amount of green malt. This is prepared in a tub above the cooker
and is dropped into the cooker when the temperature is down to 140°
to 145° F. The diastase in the malt will dissolve the cooked starch
and convert it into a fermentable sugar in about fifteen or twenty
minutes, during which time the mash should be constantly stirred.
This is kept up until the test for complete conversion shows no starch.
This test consists in filtering a little of the mash into a white porce-
lain dish and adding a few drops of iodine solution (2.5 drams potas-
sium iodide and 75 grains iodine to 1 quart water and shake). If
the mixture is blue, it shows the presence of starch, and it is then
necessary to add more malt, or allow more time for conversion. The
cleaned mash is pumped tlirough the mash cooler, where it is re-
duced to the "pitching" (this means temperature in which yeast
can ferment) temperature, by circulating a constant stream of cold
water aroimd the pipes through which the mash goes. Tliis tempera-

276 The Potato

turemost favorable to fermentation is between 60° and 70° F., depend-
ing on the weather conditions and vohime of the mash. At the same
time the mash is run through the fermenter the yeast mash (about
3 per cent by volume of the main mash) is also added. It is prepared
in a tube above the fermenter and can be dropped into it.

Fermenting the mash. — After the yeast and mash are in the fer-
menter, the process of fermentation will begin and the sugar in solu-
tion will be broken down into alcohol and carbon dioxide gas. The
gas goes out into the air, and the alcohol remains. At this point,
it is important to know the gravity and acidity of the "set mash" —
as it is now called. The specific gravity indicates the amoimt of
sugar and is ascertained as follows : Stir mash and filter small por-
tion through cheesecloth into a cylinder. A Balling saccharimeter is
placed in the filtered liquid. The reading at the level of the liquid
should be 16° to 18°, showing that the mash contains 16 to 18 per
cent of solids, most of which is sugar. The acidity of the set mash is
determined by neutralizing a small portion of the mash in a normal
solution of sodium hydroxide, and the amount of the latter required
will represent the acidity of the mash. It is done in the following
way : 20 cubic centimeters of the filtered Hquid is placed in a beaker
and the sodium hydroxide is blowly dropped in from a burette until
the filtered liquid has been neutralized and will not turn blue litmus
red or red litmus blue. The number of cubic centimeters of sodium
hydroxide used will represent the acidity of the mash. After the mash
has been set for ten or twelve horn's, the fermentation will become
vigorous and the temperature will rise. It should not be allowed
to go above 80° F. or much of the alcohol will evaporate. To keep
the mash cool, a coil with cold water passing tlirough it is slowly
raised and lowered through the mash. The fermentation is allowed
to continue at a temperature of 60° to 80° F. for 72 hours. The
gravity should fall and the acidity remain about the same diu"ing the
process. The tests should be made every 24 hours. If the acidity
rises too much, the fermenters are scrubbed clean with a 5 per cent
solution of formalin or other disinfectant. This will clean out the
butyric acid which often is the cause for raised acidity.

Distilling the alcohol. — In Fig. 27 is shown a distilling apparatus
adapted for the economic separation of alcohol from the mash. It
is not complicated, as one would think at a first glance, but is very
simple. The fermented mash is slowly pumped into a distilling ap-
paratus, where it is brought into contact with live steam, which boils

Uses of the Potato

277

Fig. 27. — Distilling apparatus for making alcohol from potatoes.

278 The Potato

it and carries away the alcohol in vapor form, which in turn is passed
through a condenser, where it is reduced to a liquid. The distilling
apparatus consists of two copper columns, A and B, A being to dis-
til the alcohol from the mash and B where it is redistilled and raised
to desired strength. The fermented mash is continually discharged
from pump 1 and pipe 2 into mash heater 3. This heater is made
up of a series of tubes through which the mash gas goes and around
which the vapors from the boiling mash are passed when going from
A to B. The heated mash leaves 3 through pipe 4 and comes in con-
tact with steam. The mash goes tlirough a series of chambers, where
it is boiled and the alcohol relieved from it. This mash takes a down-
ward course from one chamber to another, and its course may be
followed by the shaded portions in A . By the time it reaches the bot-
tom, the mash will lose all its alcohol, and this mash will be automati-
cally discharged through 5. A small portion of the vapors will be
sent through pipe 6 to the condenser 7, and be tested to see whether
any alcohol is being lost in the "slop," as the discharged mash is
called. The steam necessary to boil the mash comes into the
bottom chamber tlirough 8, and it boils the mash in this chamber and
passes upward, boiling the descending mash in the various chambers
and carrying with it the vapors. The plates within column A are
so perforated as to allow the ascent of the vapors through it, but
do not allow the mash to fall through it, because of the steam pres-
sure. The vapors rise up through A and go through pipe 9 to the
heater 3, where they are circulated around the tubes and then carried
through pipe 10 over to B. The vapors coming from A contain a
considerable amount of moisture and other impurities which are
freed in B, which contains a series of chambers upon each of which is
carried about 3 inches of liquid. The plates are not perforated in this
column, but the vapors ascend tlirough a central pipe and are de-
flected downward by a hood over the pipe in each chamber and are
forced to boil their way through the liquid in each plate. The
arrows show their courses. These vapors become piu-er as they
ascend until they reach the top chamber, from which they are de-
livered to pipe 11 and thus into a cooler 12, where they are partially
cooled. From the cooler they pass into pipe 13 and through it to
the condenser 14, where they are reduced to a liquid. This cooling
and reducing is done by circulating cold water around the tubes con-
taining the vapors. The condensed vapor or alcohol is drawn off at
the bottom of the condenser and allowed to flow tlirough the test box

Uses of the Potato 279

15, where it can be examined for its purity and strength. The
steam pressure in the apparatus is registered by the pressure gauge

16. The alcohol afterwards passes tlirough the test box into the
storage tank 17 to be denatured.

Wood alcohol and benzin are generally used as denaturing agents,
though other ingredients may be used. The ingredients used must
be authorized by the Bureau of Internal Revenue.

Preparation of green barley malt. — There are two operations —
the first being to steep or soak the grain, and the second, sprouting
or growing it. The steeping consists of soaking the grain in water
until it has absorbed sufficient moisture to enable it to sprout when
spread upon the malting floor. Good barley malt can be obtained
from a good grade of barley properly steeped (for two or tliree days)
and grown for a long interval of time (12 to 20 days) with a fair
amount of moisture at a temperature not to exceed 60°-63° F. The
malt should be thoroughly crushed before using.

Control of operation. — It is advisable to operate a distillery only
during the colder months, for instance from early autumn until late
spring. During this time the temperature of the cooling water will
be considerably lower, and the amount of water required correspond-
ingly less, and the time required for cooling decidedly shortened.
This means a shorter working day and consequently less Avear on the
machinery and a considerable saving of fuel. It is essential that a
distillery be oj^erated daily and not intermittently, as each day's work
depends in a greater or less degree both upon that of the preceding
and the following day. Another very important point is cleanliness,
and upon this depends the final yield of alcohol in a great measure.
Many injurious organisms will breed and work into the mash and
hinder the process of fermentation. This may be remedied by run-
ning water through the apparatus at the end of the day's work, and the
walls of the building should be kept from mold by whitewashing.

Preparation of a potato-yeast mash. — The yeast mash is prepared
in a wooden tub equipped with a rake for stirring and with proper
piping for heating and cooling. The volume of the yeast should be
from 2 to 3 per cent of the main mash to be fermented and increased to
ten times that of the yeast mash used to start it. Rye is best used
to start with, and later the potatoes may be substituted. The rye
and malt are mashed together. The malt should be left to work for
about three hours, by which time the formation of the sugar will be
complete. The gravity should be 20°-24° Balling. Then the mash

280

The Potato

is soured by the addition of some acids (lactic acid is best) which will
suppress organisms which infect starchy materials. It will take be-
tween 24 and 48 hours to reacli the right acidity, which is 2.5 or 3 cubic
centimeters. Then heat and then cool. When temperature is about
90° F., add the yeast (about 10 per cent of volume of mash). Then
reduce the temperature to 60°-70° F. Allow to ferment for 24 hours,
diu"ing which time the temperature will rise, but never allow it to get
above 90° F. Then this can be used in needed quantities to be added
to the main mash.

USE AS STOCK FOOD

The value of the potato as a food is great, for it is a
very concentrated starchy food. When fed alone, it is in-
capable of supplying all of the wants of the body. Ex-
periments by Girarde showed that the feeding of too
many potatoes to stock would decrease the digestibility
of the protein, the fat and the crude fiber :

Table

XXII

1

s
S

1

i

5§

g

a

W

o

1

Q

^

(X,

6

Per
Cent

Per

Cent

Per

Cent

Per

Cent

Per

Cent

Per

Cent

Per

Cent

Potatoes . . .

Pigs

97.0

84.5

82

91.8

44.6

Potatoes cooked .

Pigs

95.0

82.0

80

97.6

40.0

Potatoes dried and

ground . . .

Sheep

80.1

81.5

19.5

42.0

(From S. Fraser. "The Potato.")

It was also found to have increased the time of churn-
ing butter from 36 to 86 minutes. There was no effect
on the milk composition, but it did affect its behavior
towards rennet, injuring the milk for cheese-making.

Potatoes when fed to pigs have been shown to be al-
most entirely digestible.

Uses of the Potato 281

Snyder found that potatoes, when fed with grains or
some milled products hke oil meal, beans or good wheat
screenings, were very suitable for fattening purposes.
In experiments with sheep and cattle a ration composed
chiefly of potatoes afforded rapid gains in live weight, a
large percentage in dressed weight of the slaughtered
animals and flesh of excellent quality.

Experiments in Minnesota have shown that potatoes
are very digestible ; when 100 pounds are fed to pigs,
23.8 pounds dry matter are digested, while only 75 pounds
are indigestible. At the Hohenheim and Proskern sta-
tions, the results on this question showed that they may,
for practical purposes, be assumed to be completely diges-
tible. Snyder, at the Minnesota Station, found that
though cooked potatoes were eaten in greater quantities,
the digestibility was not increased.

Thus, it can easily be seen that potatoes, especially
when abundant and low in price, may be fed to all kinds
of stock. In France, Girarde fed 55 to 66 pounds of
cooked potatoes a day to fattening steers and 4^ to 6^
pounds to sheep. Von Fanche found uncooked potatoes
good for all stock except pigs. He fed 60 pounds raw
potatoes, 6 pounds oil meal and 9 pounds clover hay with
salt to a 1000-pounds live weight a day to fattening steers.
For milch cows, 25 pounds daily to a 1000-pounds live
weight is the limit. For yearling ewes and wether sheep
25 pounds to a 1000-pounds live weight a day is advised,
and for fattening sheep 40 pounds. For horses about
12 pounds to a 1000-pounds live weight may be given
with other food.

Stock should not be watered soon after feeding potatoes,
but preferably about i hour before feeding. Potatoes
are not valuable as a food for young animals as they are

282

The Potato

deficient in protein and ash, hence should not be fed to
growing cattle under two years old, lambs and young
pigs, unless in small amounts.

Alcohol slops or residue

The residue remaining from the production of alcohol
contains all the constituents of the materials employed,
except that portion of the sugars and starch which was
converted into alcohol during the fermenting period.
This "slop" has been found, both in this country and
abroad, to be a feeding stuff of high value, and should be
fed to the stock which furnishes the fertilizer for the
potatoes to be used in the distillery.

Table XXIII
Composition of the Slop

Ash

Protein
N.X6.25

Fat

SUQAB

Stakch

Crude
Fiber

N. F. E.

Potato. . .
Potato skins .
Slops . . .

Per Cent

4.39

6.51

11.26

Per Cent

10.06
21.87
30.00

Per Cent
0.29

2.55
0.69

Per Cent

1.59
1.44
2.29

Per Cent

70.35
8.65
2.98

Per Cent
2.26

20.69
6.54

Per Cent

10.55
28.40
46.24

(From the U. S. D. A., Farmers' Bui. 410.)

This table shows that the dry substance of the slops is
a higher nitrogenous food than the potato. It is due to
the fermentation of the starch and sugar resulting in a
concentration of the nitrogenous material.

Uses of the Potato 283

Potato pomace

Potato pomace is the residue which is left in the manu-
facture of starch from potatoes. It contains nearly all
of the fiber, protein, fat and a large part of the starch
found in the fresh potato. As it comes from the factory
it has incorporated in it a large amount of water.

In this country this pulp mass goes to waste, but in
Europe the potato and beet residue are rather extensively
used as feeds in the wet condition, 80 pounds to 125
pounds being fed to cattle daily a head. There, however,
the factories are running throughout the year, and the
residue can be fed in the wet state. But here this is not
possible, and as the wet residue cannot keep, some method
must be devised to dry it out, for in the dry state it will
keep well.

Poultry food

T. W. Saunders, in his book on the potato, very highly
recommends the use of potatoes as a poultry food. When
given in correct proportion, it will do good in a food. The
starchy part of the potato is mainly used in maintaining
the heat of the body. It is cheap and easy to prepare
and generally liked by all classes of poultry. To get the
right proportions, of course, one must take into considera-
tion the condition of the birds, weather, temperature,
method of housing, extent of liberty allowed and whether
the birds are expected to produce eggs or to lay on fat
and flesh.

A cheap good diet used for layers that are at liberty is
equal parts by weight of potato and bran. The potato
should be boiled, and the latter mashed into the potato
while hot and the mixture given warm. If the weather

284. The Potato

is cold, add some linseed oil or fat. For confined layers,
the proportion of potato should be reduced. Malt culms
or sprouts are very good in combination with potatoes.

Indian meal, barley meal and rice meal should not be
fed in combination with potatoes, for they lack nitrogen
matter.

For fattening poultry, large amounts of potato can be
used. Ducks, geese and turkeys fatten well on a mixture
of potato and midds.

Dried dessicated potatoes

In Germany the manufacture of potato cakes is estab-
lished, and these can be used as a food. The cakes, of
course, are much smaller in bulk than the fresh potatoes,
but after the soaking in water before using, their original
character is regained. While the flavor and appearance
cannot equal those of good fresh potatoes, they are con-
sidered appetizing and acceptable where fresh ones are
unobtainable. In this form they can be easily preserved
in the tropics and in the arctic region and thus furnish
an excellent article of diet in a convenient form for trans-
portation.

Potato flour

In Germany the manufacture of potato flour is very
much advanced. Rye flour is improved for baking by
its addition. During the winter of 1914-1915, when
there was a shortage of flour, owing to the European
war, potato flour was used to make cakes and bread.
Cakemakers and confectioners used it mixed with wheat
flour.

Uses of the Potato 285

REFERENCES

Canon, Helen.

1915. Potatoes in the Dietary. Cornell Reading Course Bui.,
Food Series No. 15.
Oilman, J. W.

1905. Quality in Potatoes. Cornell Bui. 230, pp. 503-525.

GiRARDE, A.

Potatoes as a Food for Cattle and Sheep. Journ. Agr.
Proc. 59 (1895), No. 20, pp. 709-712.
Grubb, E. H.

1912. The Potato. N. Y. (Doubleday), p. 545.
Henslow, G.

1910. Origin and Best of Our Garden Vegetables and Their

1911. Dietetic Values. Roy. Hort. Soc. Journ., 36, pp. 345-
346.

Lang WORTHY, C. F.

Potato as a Food. U. S. D. A., Farmers' Bui. 295.
NiviERE and Humbert.

1895. Manufacture of Potato Cake. Abs. in Joiu-n. Bd. Agr., 2

(1895), No. 2, pp. 190.
Parow, E. Potato Drying in (Germany. Mitt. Deut. Landw.

Gesell., 21 (1906), No. 25, pp. 264-266.
Searl, O., Springer, J., and Kjus, M. J. Manufactiue of Potato

Starch. Tidsske-Norske Taudbr., 4 (1897), No. 5, pp.

203-208.
Skinner, A. P.

1910. Manufacture of Potato Spirit in Germany. Daily

Cons, and Trade Repts. (U. S.) 13, No. 148, 1167-

1169.
Smith, C. D.

1896. Feeding Value of Potatoes. Mich. Sta. Rpt. 107.
Snyder, H. The Composition and Digestibility and Food Value

of Potatoes. Minn. Sta. Rpt. 8 (1895), 83-96.
Wente, a. O. Potato Culls as a Source of Industrial Alcohol.

U. S. D. A., Farmers' Bui.
Wiley, H. W. The Manufacture of Starch from Potatoes and

Cassard. U. S. D. A., Div. of Chem., Bui. 58, pp.

286 The Potato

Wiley, H. W. Potato as a Food. Compt. Rend. Acad. Sci., Paris

(1897), No. 1, pp. 43, 4G.
Wiley, H. W. Potato as a Food for Milch Cows. Journ. Agr.

Pract., 58 (1894), No. 28, pp. 46-17.
Wiley, H. W. Potatoes as a Food for Beef Cattle and Sheep.

Journ. Agr. Pract., 58 (1894), No. 28, pp. 43, 46.

CHAPTER XV
COST OF GROWING POTATOES

The cost of growing potatoes is very variable, depend-
ing upon many factors. The cost not only varies among
different sections of the country, but among farmers in
the same section. The price of land, use of machinery,
amount of spraying and extensiveness of operations are
only a few of the factors which determine the cost. When
figures are compared from many areas, however, a con-
siderable uniformity is found to exist.

Costs are given in the following pages from widely
separated areas. They will give the reader a fairly
accurate idea of the average expense involved in growing
an acre of potatoes in different regions.

Place — Twin Falls County, Idaho.

Authority — Grubb and Guilford, "The Potato."

Detailed cost of producing a 150-bushel crop as fol-
lows : —

Plowing $3.00

Harrowing .75

Floating 1.00

Seed, average planting 700 pounds at 2 cents 14.00

Planting 2.50

Irrigating first year 5.00

Cultivating three times at 50 cents .... 1.50

Digging 1.50

Picking — 150 bushels at 4 cents .... 6.00

Sacks — 75 at 7 cents 5.25

Hauling to pit 2.00

Total .S44.00

287

288 The Potato

"If potatoes are worth 50 cents a bushel, this crop
would sell for $75, leaving a profit of $30.50 per acre,
not deducting rent or interest or taxes.

"If, however, the grower produces a 600-bushel crop,
the cost of producing (figuring twice as much seed and
increased cost of the operations) would be about $95.75.
The crop would sell (at 50 cents a bushel) for $300, leav-
ing a profit of $204.25."

Place — Colorado.

Authority — Greeley Commercial Club.

Plowing $2.50

Leveling and harrowing 1.00

Seed 5.00

Planting 1.50

Cultivating 2.50

Irrigating 1.50

Digging 7.50

Sacks 7.50

Marketing 6.00

Total $35.00

"This estimate is based on what is considered a good
yield of from 200 to 300 bushels per acre. The first six
items are practically uniform whatever the yield may be,
while the last three depend upon the yield per acre, so
that a poor yield or a failure reduces the cost per acre
by about one-half and an extremely large yield increases
it accordingly.

" The price of Colorado potatoes has a wide range from
year to year, but the average price for the past ten years
has been 65 cents per hundred pounds."

Place — Kansas. Forty representative growers from
thirty-two different counties.

Authority — Report of Kansas State Board of Agri-
culture, 1904.

Cost of Growing Potatoes 289

Average cost of plowing $1.20

Harrowing 54

Seed 7.25

Planting 1.35

Cultivating 1.66

Digging and marketing 8.85

Wear and tear of tools and rental of land or

interest on its value 4.42

Total cost per acre, or 122 bushels . 5»25.27

Averages of other items, gathered from those furnish-
ing the forty foregoing reports, are as follows :

Average number of years each of the forty reporters has

raised potatoes in Kansas 18

Average number of acres raised by each annually ... 26

Average quantity of seed planted per acre (bushels) . . 9

Average yield per acre (bushels) 122

Average value of potato land per acre $60

Statements of ten of the growers reporting who are
most extensively producing potatoes for commercial
purposes, in the-Kaw Valley, average as here shown :

Average cost of plowing $1.45

Harrowing .51

Seed 8.05

Planting .65

Cultivating 1.46

Digging and marketing 11.00

Wear and tear of tools and rental of land or

interest on its value 6.85

Total cost per acre, or 154 bushels . $29.97

Average number of years each of these ten reporters has

raised potatoes in Kansas 18.0

Average number of acres raised by each annually . . 80.0

Average quantity of seed planted per acre (bushels) . 10.4

Average yield per acre (bushels) 153.7

Average value of potato land per acre $105.00

u

290 The Potato

Place — Ohio.

Authority — Terry, T. B., and Root, A. I., "Potato
Culture."

Yield per acre — 250 bushels.
Average price — 40 cents.
Profit per acre — $61.06.
Detailed cost as below : —

Plowing $2.00

Harrowing with Thomas and three horses .33

RoUing 25

Eight bushels seed at 50 cents, average . 4.00

Cutting to one eye 1.50

Planting with planter 1.00

Harrowing three times 45

Harro^ving four times with weeder ... .80
Cultivating eight times, once in a row . . 3.36

Bugs 2.00

Hand pulling or cutting weeds 75

Digging with four horses 2.50

Picking up and storing 3.00

Marketing, three-mile haul 6.00

Manure 5.00

Interest on value of land $100, at 6 per cent 6.00

$38.94

Dodge says: "The more expensive method of growing
potatoes usually gives a yield of 275 bushels or more to
the acre. Unless an application of barnyard manure is
made in addition to the expense estimated at an added
cost of from $5 to $10 per acre, the less expensive method
rarely produces more than 125 bushels per acre and in a
great many instances decidedly less than 100 bushels per
acre. The increase in yield as a result of the more costly
method is sufficient to more than pay the difference in
cost, supposing potatoes to sell as low as 33§ cents a
bushel. One hundred and twent>'-five bushels per acre
grown at a cost of $15 per acre and sold at 33f cents a

Cost of Grotving Potatoes

291

bushel yield a net profit of $20.66 per acre. Two hun-
dred and seventy-five bushels ])er acre grown at a cost of
$00 per acre and sold at 33 1 cents per bushel yield a
net profit of $31.66 per acre. The second profit is $5
more per acre than the first.

"A farmer in Van Buren County, Michigan, states
that his potato crop, mostly marketed in the fall, sold at
an average price of 44 cents a bushel for a period of ten
years. At the latter price the more expensive method of
culture would yield a profit of $61 per acre, against
$40 from the cheaper method. Furthermore, some of
the leading potato dealers of the North have stated em-
phatically that a better quality of potatoes is normally
obtained with large yields than with small."

Place — Maine and Wisconsin. Dodge says the Wis-
consin figures will represent the expense put into grow-
ing the crop in most localities where potato growing is
carried on, on a less expensive and thoroughgoing basis.

Authority — Dodge, L. G., Farmers' Bui. 465.

Cost op Supplies and Labor with
Rent of Land

Maine

Wisconsin

Plowing

Harrowing

Fertilizer

Seed

Cutting

Planting

Cultivating

Spraj'ing

Digging

Rent of land

Total

$1.50

.50

24.00

5.00

.75

.75

3.50

3.00

6.00

15.00

$60.00

$1.25
.25

2.50
.60
.60

1.90
.80 >

2.10

5.00
$15.00

For beetles only.

292 The Potato

Place — INIaine.

Authority — Bulletin of the Maine Department of
Agriculture, March, 1914.

Average cost of one acre of potatoes from records of
ten potato growers in different localities in the state : —

Cost of plowing $2.85

Harrowing four times 4.00

Fertilizer 36.00

Applying 2.00

Seed, 13 bushels at 80 cents 10.40

Cutting seed 1.75

Planting 4.00

Cultivating four times 4.00

Hoeing three times 3.00

Spraying five times at $1.15 5.75

Harvest 14.00

$87.75

Place — Maine.

Authority' — Cleveland, E. L., Aroostook County,
Maine.

Commercial fertiUzer 1500 to 2000 pounds . $28.50 to $35

Preparing ground for seed 3.00

Seed, 600 pounds 7.00

Planting 2.50

Cultivation 3.50

Gathering or harvesting 7.50

Preparing for market .50

Wear and tear on implements .50

Rent of land (tenant farmer pays) .... 10.00 to 20

Bordeaux mixture 4.00

Paris green .50

Hauling to market 3.50

Average yield of product per acre .... 220 bushels

Average value of product per acre .... $88.00

Average size of fields 15 acres

Average value per acre of land growing such

crops $75.00 to $100

Profit per acre 17.00

Cost of Growing Potatoes 293

"Much depends on the weather conditions as to the
cost of applying bordeaux mixture, paris green, cost of
cultivation, labor and general net results.

"The above estimates may be regarded the average
for a series of years."

Place — Maine.

Authority — Hurd, Prof. W. D., formerly dean of the
College of Agriculture, University of Maine.

From records for several years on the college farm at
Orono, the cost of growing a ten-acre field of potatoes is
about as follows : man and team labor are reckoned at
$3.50 per day, extra men at $1.50 per day.

Plowing at $2 per acre $20.00

HarroAS-ing five times, $3.50 per acre 17.50

Fertilizer (home mixture) $30 a ton 225.00

Seed, 130 bushels, 75 cents a bushel 97.50

Disinfecting seed (labor and material) 3.00

Cutting seed (by hand) at 6 cents per bushel . . . 7.80

Planting, team and two men three days, $5 . . . . 15.00

Harrowing or weeding before crop is up, four times . 10.50

Cultivating crop eight times at $3.50 28.00

Spraying six times ($1 per acre each application) . . 60.00

Hand hoeing and pulling weeds once (if necessary) . 15.00
Digging and hauling to storehouse or station at $15

per acre 150.00

Rent of land (5 per cent on $50 per acre value), 10

acres , 25.00

Depreciation of implements (plows, harrows, planter,

sprayer, digger, etc.), value $250 estimated at 10 per

cent 25.00

$699.30

Value of crop, 225 bushels to acre (2250 bushels at 50

cents) $125.00

Value per acre 112.50

Cost of growing per acre 69.93

Net profit per acre 42.57

294

The Potato

Place — New York.

Authority — Results of a survey by the Department
of Farm Management, New York State College of Agri-
culture.

Cost of Growing Potatoes

1913

1914

Number of farms

Number of acres

Average acres per farm . . .
Average yield per acre . . .

18.0
185.4

10.3
102.7

21.0

158.8

7.6

154.7

Cost of Growing per Acre

Amount

Amount

Seed

10 bu.

$7.67

12.6 bu.

$8.03

Fertilizer . . .

412 lb.

5.17

431 lb.

5.72

Manure . . .

6.14

2.06 tons

4.64

Spray materials

.83

.80

Man labor . .

77.7 hr.

13.30

81.2 hr.

15.57

Horse labor . .

77.4 hr.

10.66

72.4 hr.

12.41

Equipment . .

3.58

3.71

Use of land at 6 per cent

4.53

5.18

Use of buildings at 8 per

cent

1.27

1.09

Interest at 5 per cent .

.88

All other costs . . .

.63

.04

Total cost . . .

$53.74

$58.07

Cost of marketing pei

bushel

.12

.05

Cost of growing per bushe

.52

.38

Cost of gromng and mar-

keting per bushel

.63

.43

Profit per acre . . .

7.38

-16.03

Profit per bushel . .

.07

- .10

Profit per man, hour .

.08

- .18

Cost of Ci wiring Potatoes

295

:JLJ Ijb

Apr. May June July Aug. Sept. Oct.

Apr. May June July Aug. Sept. Oct.

Fig. 28.

(see page 298)

Fig. 29.

Place — California.

Authority — Shaiiklin, L. F., Lompoc, California.
Quoted from Grubb and Guilford, "The Potato."

L. F. Shanklin of Lompoc, California, estimates the
cost of producing an acre of potatoes as follows : —

Use of land (wiU rent for) 130.00

Seed, 400 pounds at 1| cents 6.00

Plowing and preparation 5.00

Cultivation twice — hoeing once 1.00

Digging and picking 3.00

Sacks 5 cents, sacking 5 cents (100 sacks) 10.00

Hauling 1.00

$56.00
His average crop is : —

70 sacks first, 115 pounds to sack, at $1.30 per 100 . . $80.00
30 sacks seconds, 120 pounds to sack, at $1.00 per 100 . . 36.00
30 sacks cow feed or waste at 10 cents per 100 . . . 3.00

$119.50

Place — New York.

Authority — Department of Farm Management, New
York State College of Agriculture.

Cost of Growing Potatoes
IN New York

Steuben Co.

Clinton & Franklin
Cos.

No. farms

Yield per acre ....
Acres per farm ....

355.0

131.0

14.7

300.0
179.0

7.2

296

The Potato

Cost op Growing

Amount

Amount

Seed

Fertilizer

Manure

Spray materials . . .

Man labor

Horse labor

Use of equipment . . .

Land

Buildings

All other costs ....
Total cost of growing per

acre

Total cost of growing per

bushel

Cost of marketing per acre
Cost of marketing per

bushel

Profit per acre ....
Profit per bushel . . .
Profit per man, hour . .

10.2 bu.
120.0 lbs.
2.3 tons

66.0 hrs.
68.9 hrs.

$9.48

1.66

4.61

.20

11.55

10.33

3.45

3.00

.81

.45

45.54

.35

.054
2.22
.02
.03

12 bu.
407 lbs.
3.4 tons

110.4 hrs.
88.6 hrs.

$6.79

5.77

7.21

.22

17.65

10.20

3.94

7.00

1.56

.12

60.68

.33
6.32

.044
36.72
.21
.33

Place — Utah.

Authority — Harper, W. F., Smithfield, Utah. Quoted
in Grubb and Guilford, "The Potato."

Plowing, harrowing and leveling the land $5.00

Fifteen loads of manure at 25 cents per load .... 3.75

Hauling manure at 75 cents per load 11.25

Seed 10.00

Cutting and planting seed 9.00

Cultivating, weeding and irrigating 5.00

Picking and sacking 10.00

Loading on car 4.50

$59.00

Results of a survey in New York state

In the agricultural survey of Tompkins County,
Warren, Livermore, and others: "The potato crop ranks

Cost of Growing Potatoes 297

third in value of crops, but the acreage per farm is very
small, averaging 1.7 acres. Of 982 farms in four town-
ships, only 33 grew more than 5 acres of potatoes and only
2 grew over 10 acres. Nearly all of the crop is grown in
this small way, but the crop is usually a profitable one.

"Apparently the larger acreages are profitable. The
average labor income of farmers growing more than 5
acres of potatoes is $853.

"Of 605 farms operated by owners, 11 sold over $500
worth of potatoes. These men made good profits. The
lowest labor income was $724, and the highest $2146;
the average was $1511. The farms averaged 141 acres.
An average of 6.3 acres of potatoes were grown per farm,
with an average yield of 219 bushels per acre. The
average receipts from the sale of potatoes were $732,
which constituted 24 per cent of the total sales.

"Of nine of these farms the most important sale was
milk, with potatoes second. Each of the farms received
some income from hay, grain, eggs, or lambs, etc.
The average labor income on these farms was $1575.

"One farm of 134 acres was a potato, hay and grain
farm, with some sales of eggs, milk, etc. This farm gave
a labor income of $1649.

"One farm of 71 acres sold potatoes, lambs, hay, grain,
eggs, etc., and made a labor income of $794. On many
farms that have soils adapted to potatoes, it would seem
desirable to increase the area of this crop. When the
crop can be increased to ten acres per farm, it will justify
the purchase of a planter, sprayer and digger. Only
by growing a much larger acreage per farm can one afford
this labor-saving machinery that will go far toward
making the crop pay. It will also pay to try much
heavier applications of fertilizer."

298 The Potato

Other survey results

In a survey of the incomes of 178 New York farms,
Burritt ^ obtained some interesting figures which show
comparisons of certain kinds of farms. Unfortunately
the number of potato farms in the survey was very small
and may not mean very much, but the tables give a
suggestive comparison. He says : " All farms were di-
vided into two classes. Mixed or general farms are those
on which no one source of income constitutes 40 per cent
of the total income. Special farms are those deriving
40 per cent or more of their income from one special
crop or industry. This latter class was further divided
into dairy, fruit, potato and truck farms."

The seasonal distribution of man and horse labor is
one of the factors which determine the feasibility of
growing potatoes along with other crops, and represents
no small measure of profitableness when considered in
the whole farm scheme. The figures 28 and 29 (page 295)
are used by Warren to represent the distribution of
horse and man labor respectively, on 1 1 acres of potatoes.
Black is work fixed as to time, white is plowing and
marketing.

1 Bui. 271, Agri. Expt. Sta., Cornell University.

Cost of Growing Potatoes

299

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300

The Potato

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Cost of Growing Potatoes

301

m

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a> t^ to lo Oi CO '^

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a

OCOlMiCOSOOCOiOO

CO»Or-icOiM0000cO05 ■
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No. of farms . . .
Average area . . .
Total capital . . .
Real estate ....
Machinery and tools

Horses

Other live stock . .
Seed and feed . . .
Miscellaneous . . .

302

The Potato

a

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No. of farms . . .
Total paid labor . .
Unpaid family labor .
Board of laborers . .
Total labor except

owner's ....
Farmer's estimate of

value of his own

labor 1

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Cost uf Growing Potatoes

303

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so

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No. of farms . . .
Total expense . . .

Labor

Seed and feed . . .
Fertilizers ....
Machinery and repairs
Building and fences .
Live stock ....
Miscellaneous . . .

304

The Potato

Place — New York (St. Lawrence County).

Authority — Circular of Information of the New York
State School of Agriculture at St. Lawrence University,
April, 191L

The detailed cost of growing an acre of early potatoes
for the years 1909 and 1910 was as follows : —

Early Potatoes

Cost per Acbb

1909

1910

Yield (large), 192.22 bushels at 62 cents
Yield (small), 26.65 bushels at 20 cents
Yield (large), 122.15 bushels at $.477 .
Yield (small), 22| bushels at 20 cents .

Plowing

Harrowing

Planting

Cultivating

Hoeing

Spraying

Digging and delivering

Fertilizer, 2000 pounds

Fertilizer, 1899 pounds

Seed, 18i bushels at SI. 18

Seed, 17i bushels at S .40

Paris green

Total cost per acre

Profit per acre

Loss per acre ,

$119.18
5.33

$95.29
29.22

$58.27
4.50

4.00

2.01

4.39

2.25

4.42

4.29

1.93

3.01

1.81

.87

8.49

9.39

18.19

14.61

28.00

25.72

21.66

6.90

2.40

2.92

$71.97
9.21

"The soil upon which the main crop of late potatoes
was grown is a sandy loam. The field had no clover
sod, indeed, no sod of any sort except the quack-grass and
weeds. A higher cost for chemicals was necessary to
make good this deficiency. Three and one-third acres
of the field contained quack-grass and foul seeds. This

Cost of Groiving Potatoes 305

land was plowed twice in the spring with frequent culti-
vation, which very nearly destroys every trace of quack-
grass. The low cost of hand labor on the field warrants
the statement that weed growth was practically de-
stroyed by cultivation before the potatoes were planted,
and by the weeder after they were planted. It is impor-
tant that we impress upon the users of weeders and smooth-
ing harrows the absolute necessity of beginning opera-
tion at once after the potatoes or seeds have been planted.
If the weeds become rooted, even though they may not
show very much above ground, the light-fingered tools,
which are only safe to use on the growing plants, will
have very little eft'ect upon them. Farmers are often
disappointed in the effect of weeders, simply because the
weeder has given the weed the same encouragement which
it gives to the plant under cultivation.

"The seed potatoes which were kept in an outdoor pit
during the winter were taken from the pit April 18th,
spread thinly on the barn floor and stirred occasionally to
prevent long sprouts from growing. They were planted
at varying dates from May 28th to June 10th. None
of the sprouts were broken in handling or planting. The
pieces were cut as nearly cubical as possible, and weighed
about 2 oz. each. The number of eyes varied from 1 to
5, the seed ends often containing 5 to 6 eyes. No eft'ort
was made to reduce the size of the seed piece from the
seed end of the potato, in fact it is a fatal error to do so.
Only one or two stalks will develop. The pieces were
dropped 14^ inches by 36 inches."

"The cost by items does not show marked difference
for the two years, with the exception of digging and
delivering. A part of this saving was due to a lighter
yield and a part to more economical methods of handling."

306 The Potato

Four and One-third Acres Potatoes (1910)

Yield, 9581 bushels (large) at 40 cents
Yield, 53 bushels (small) at 20 cents .

Plowing

Harrowing

Planting

Cultivating

Hoeing, hand labor

Spraying, 1050 gallons per acre . . .

Digging and delivering

732 bushels seed at 40 cents . . .

8234 pounds fertiUzer

42 pounds paris green

Profit, S75.87

$15.33
9.75
18.63
13.02
3.81
40.70
63.32
29.40

111.57
12.60

$383.40
10.60

$318.13 $394.00

Potatoes

Cost per Acre

1909

1910

Yield (large), 289| bushels at 40 cents
Yield (small), 27 bushels at 20 cents .
Yield (large), 221J bushels at 40 cents
Yield (small), 12.2 bushels at 20 cents

Plowing

Harrowing

Planting

Cultivating

Hoeing (hand labor)

Spraying, 1000 gallons

Spraying, 1050+ gallons

Digging and delivering

Seed, 16 bushels at 73 cents . . . .
Seed, 17 bushels at 40 cents . . . .

Fertilizer, 1800 pounds

Fertilizer, 1900+ pounds

Paris green, 7 pounds

Paris green, 9.6+ pounds

Total cost per acre

Profit per acre

$115.92
5.40

4.18
1.90
4.30
1.73

.68
8.49

24.01
11.68

25.20

2.10

$84.27
37.05

$88.48
2.44

3.54
2.25
4.30
3.00

.88

9.39
14.61

6.80

25.75

2.91

$73.43
17.49

Cost of Growing Potatoes 307

Place — Minnesota.

Authority — Bulletin 48, Bureau of Statistics, by Hays
and Parker.

The cost of producing potatoes, under garden condi-
tions, is given on pages 308 and 309.

Cost of hauling

Potatoes are a bulky crop and the cost of hauling is
no inconsiderable item. Andrews ^ says : " In many ways
they are hauled under conditions similar to those under
which grain is hauled, and the average cost per 100 pounds
for hauling potatoes from farms to shipping pomts is the
same as for wheat and 2 cents more than for oats, corn
or barley.

"The averages for the United States are affected more
by the figures for the north Atlantic and north central
states than by the other states and the territories, since
about three-fourths of the potato crop of the United
States is produced east of the Rocky ]\Iountains and
north of the Potomac and Ohio rivers and southern
boundaries of Missouri and Kansas.

"The average cost of hauling from farms to shipping
points in this region is 9 cents per 100 pounds, or 5.4
cents per bushel. The lowest average cost is for three
counties in Rhode Island, where an average of three trips
per day is made to and from shipping points, and the
highest average cost in the north Atlantic and north
central states is in South Dakota, where the average
time of round trip between farm and shipping point is
longer than one working day."

' Andrews. Cost of Hauling Crops from Farms to Shipping Points.
U. S. D. A., Bureau of Statistics, Bui. 49.

308

The Potato

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Cost of Growing Potatoes

309

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310

The Potato

Table XXXI.

-Average Cost op Hauling Potatoes from
Farms to Shipping Points

Il

o

Average

State or Territory

Miles
to Ship-
Point

Days

for
Round
Trip

Pounds
in One
Load

Cost
per
Load

Cost
per 100
Pounds

Maine

9

7.6

0.7

2393

$2.58

$0.11

New Hampshire . .

5

6.6

.6

2330

2.21

.09

Vermont

7

7.1

.6

2321

1.93

.08

Massachusetts . . .

3

10.6

.6

2300

2.40

.10

Rhode Island . . .

3

5.0

.3

1933

.98

.05

Connecticut ....

2

6.7

.7

2500

2.80

.11

New York ....

34

7.1

.7

2896

2.49

.09

New Jersey ....

9

4.8

.6

2583

2.08

.08

Pennsylvania . . .

22

6.6

•7

2809

2.61

.09

Delaware

1

10.6

.7

1500

2.80

.19

Maryland

7

5.7

.5

2536

1.62

.06

Virginia

22

9.1

.8

1880

2.30

.12

West Virginia . . .

17

12.2

1.2

1965

4.21

.21

North Carolina . . .

27

11.4

1.1

1437

2.92

.20

South Carolina . . .

3

9.9

.7

1267

2.01

.16

Georgia

16

11.0

1.0

1466

2.52

.17

Florida

9

7.7

.6

1544

2.05

.13

Ohio

22

7.2

.7

2748

2.39

.09

Indiana

12

6.4

.6

3075

1.72

.06

Illinois

13

6.0

.6

2700

1.94

.07

Michigan

47

8.0

.7

2766

2.25

.08

Wisconsin . . . .

28

9.5

.8

2595

2.46

.09

Minnesota . . . .

20

9.7

.8

3890

2.68

.09

Iowa

14

5.9

.5

2293

1.48

.06

Missouri

13

9.4

.8

2035

2.05

.10

South Dakota . . .

4

15.5

1.1

2950

3.51

.12

Nebraska . . . .

14

11.1

.8

2732

2.64

.10

Kansas . . . . .

6

5.2

.6

2658

1.82

.07

Cost of Growing Potatoes

311

^ W Q
gig

III
o

Average

State ob Teeritory

Miles
to Ship-
ping
point

Days

for

Round

Trip

Pounds
in One
Load

Cost
Lo"d

Cost
per 100
Pounds

Kentucky . .
Tennessee . .

19
19

8
11

6
26

3
11

12.4
10.0
14.0
11.9
12.6
12.4
7.9
13.6

1.4
.8
1.2
1.1
1.3
1.1
.6
1.3

1834

1874
1450
1336
1400
1460
1867
1523

4.44
1.99
3.14
2.85
4.00
2.86
1.65
3.04

.24
.11

.22

Mississippi . .
Louisiana . .
Texas ....

.21
.29
.20

Indian Territory
Arkansas . . .

.09
.20

Montana ...
Wyoming . .

9
5

20
3
5
4

15
9
7

14.0
25.5
12.2
22.7
10.1
15.5
7.8
9.7
12.0

1.2
2.3
1.1
2.1

.7

1.4

.8

.9

1.1

2811
2860
3100
1800
3300
3125
2617
4028
4914

5.47
9.20
4.71
9.09
2.31
5.17
3.38
3.15
4.72

.19
.32
.15

New Mexico . .

Utah ....

.50
.07

Idaho ....

.17

Washington . .

.13

.08

California . .

I :

.10

Geographic divisior
North Atlantic
South Atlantic
North Central
South Central
Western . .

94
102
193
103

77

7.0
9.6
8.1
12.1
11.3

.7

.9

.7

1.2

1.0

2717
1871
2651
1660
3615

2.55
2.74
2.30
3.30
4.05

.09
.15
.09
.20
.11

States and Territo
represented .

ries

569

8.2

.7

2679

2.34

.09

312

The Potato

Table XXXII. Cost of Hauling Potatoes prom Most
Remote Farms to Shipping Points, as Reported

State or Territory

Shipping
Point

Maine . . .
New Hampshire
Vermont . .
Massachusetts
Rhode Island .
Connecticut .
New York . .
New Jersey
Pennsylvania .
Delaware . .
Maryland . .
Virginia . .
West Virginia
North Carolina
South Carolina
Georgia . . .
Florida . . .
Ohio . . .
Indiana . .
Illinois . . .
Michigan . .
Wisconsin . .
Minnesota . .
Iowa . . .
Missouri
South Dakota
Nebraska . .
Kansas . . .
Kentucky . .

Alabama . .
Mississippi
Louisiana . .
Texas . . .
Indian Territory

16.0
13.0
15.0
19.0
10.0
15.0
25.0
15.0
16.0
15.0
12.0
46.0
40.0
50.0
15.0
30.0
24.0
30.0
15.0
24.0
30.0
30.0
30.0
13.0
20.0
30.0
37.5
9.5
37.5
35.0
37.5
30.0
25.0
46.0
15.0

Round
Trip

1.0
1.0
1.0
1.0

.5
1.0
3.0
1.5
1.0
1.0
1.0
5.0
4.0
4.0
1.5
2.5
2.0
2.0
2.0
1.5
2.0
2.0
2.0
1.0
2.0
3.0
3.0
1.0
5.0
3.0
4.0
2.5
3.0
4.0

.5

Pounds
IN One
Load

1600
2000
3000
3500
1500
2000
3000
3500
3500
1500
4000
3000
3500
1600
1600
2000
1500
2000
3250
3500
3500
2500
3000
2000
1500
3000
4000
3000
ISOO
1500
1200
1500
900
3000
2000

Cost per
Load

$3.50
4.00
3.50
4.75
1.50
4.00

12.00
5.62
4.00
4.00
5.00

20.00
8.00

11.00
3.75
5.00
5.00
8.00
6.00
6.00
6.00
6.00
7.00
3.00
3.00
7.50
9.00
2.50

15.00
8.25

10.00
6.88

12.00
7.52

13.75

Cost per

100

Pounds

Cost of Groiving Potatoes

313

Miles to

Days for

Pounds

Cost per
Load

Cost per

State or Territort

Shipping

Round

IN One

100

Point

Trip

Load

Pounds

Arkansas

40.0

2.5

2250

7.50

.33

Montana .

30.0

3.0

3500

13.50

.39

Wyoming .

55.0

6.5

4500

22.75

.51

Colorado .

70.0

7.0

2500

33.00

1.40

New Mexico

57.5

4.0

2000

22.00

1.10

Utah . . .

25.5

2.5

3000

8.75

.29

Idaho . .

25.0

3.0

2500

10.50

.42

Washington

30.0

3.0

800

12.00

1.50

Oregon . .

35.0

3.0

2000

13.50

.68

CaUfornia .

32.0

3.0

4000

12.75

.32

INDEX

Africa, production of potatoes in, 3.

alcohol, manufacture of, 274.
slops or residue, 282.
use for, 271.

alfalfa in rotation, 111, 112.

alsike clover in rotation, 111.

Aroostook County, Me., as a potato
center, 7, 113.

arsenical injury, 202.

Asia, production of potatoes in, 3.

association of characters in breed-
ing, 75.

Australia, production of potatoes
in, 3.

Austria-Hungary, production of
potatoes in, 2, 3.

bacteria in soils, 102.

bacterial wilt, 200.

Baker, 21.

barley, value in United States, 3.

world's crop, 1.
Bauhin, 15.
belladonna, 1.
black-leg, 199.
blister-beetle, 175.
bordeaux mixture, 217.
botanical characteristics, 21.
breeding, 47-85 (chapter IV).
bud-selection, 57.
bud-sports, 57, 76.

calcium, 124.

Canada, production of potatoes in,
3, 13.

de Candolle, 15.
capsicum, 1.

Carbondale, Colo., as a potato cen-
ter, 7.
Cardan, 15.

Chester County, Pa., potatoes con-
sumed on farms, 12.
Cierca de Leon, 14.
classification, 21.
climate, 86 (chapter V).
Clusius, 15.

Colorado potato beetle, 170.
composition of potatoes, 262.
constitutional degeneracy, 205.
control measures against disease,

206-225 (chapter XI).
corn, value in United States, 3.

world's crop, 1.
cost of growing potatoes, 287-313
(chapter XV).

harvesting, 234.

hauling, 307.
cotton, value in United States, 3.
cover-crops, 105.
critical period, 89, 95.
crop reporter, 257.
crossing, method of, 78.
cultivation of potato, 163.
culture of potato, 89.
curly dwarf, 203 ; control, 206.
cutting seed, 156.
cyanimid as fertilizer, 120, 121.

Dala potato, 73.
Darwin, 76.

description of potato, 22.
desiccated potatoes, 284.
digging, methods of, 230,
disease, 97.

from organisms in soil, 212.

proof varieties, 50, 221.
diseases of potato, 183-205 (chapter

X).
Dodge, 70.
drainage, 95.

315

316

Index

Early and late potatoes, marketing,

249.
early blight, 189.
East, 74, 78, 82, 83.
eastern shore of Va. and Md. as

potato centers, 7.
egg-plant, 1.
engines, 165.

England, introduction into, 15.
Europe, production of potatoes in,

3.
European Russia, production of

potatoes in, 2.
expense of marketing, 255.

family consumption, statistics, 11.
farm manures, 130.
fertilizer practices, 115, 126.
fertilizers, 113 (chapter VI).

market forms, 116.
Fischer, 75, 76.
Fitch, 25, 27, 30, 33.
flea-beetles, 173.
flour, potato, 284.
France, production of potatoes in,

2, 3.
freight charges, 253.
Fruwirth, 73, 74.
Funk, 11.
fusarium dry rot, 196.

wilt, 195.

Gerard, 16.

Germany, production of potatoes

in, 2, 3.
yields to the acre, 12.
grading, 245.
Great Britain, yields to the acre,

12.
Greeley, Colo., as a potato center, 7.
green manures, 105.
growing crop, care of, 160 (chapter

VIII).

hand planting, 151.
harvest, time to, 226.
harvesting cost, 234.

labor. 234.

potatoes, 226-235 (chapter XII).

hauling, cost of, 307.
hay-plants, 109.

value of in United States, 3.
heat, 90.
heated cars, 253.
henbane, 1.
Herbal, 16.
Heriot, 47.

hill and drill planting, 146.
\i\\ selection, 54.

history of potato, 14 (chapter II).
human food, uses as, 260.
Humboldt, 15.

hybridization, improvement by,
77-84.

ideals of the potato crop, 48, 49.
improvement, methods of, 56.
individual selection, 62.
insects, 170-182 (chapter IX).
Ireland, introduction into, 16.
Irish famine, 20.

Kaw Valley, as a potato center, 7.
Kohler, 31, 33.

late blight, 190 ; treatment, 214.
leaf-hoppers, 129.
leaf roll, 204 ; control, 206.
Livingston County, N. Y., potatoes

consumed on farms, 11.
local dealers, marketing through,

243.

McCormick variety, resistant to
heat, 91.

Macoun, 12.

Maine, production of potatoes in,
3.

manures and fertilizers, 113 (chap-
ter VI).

marketing through local dealers,
243.

markets, 249.

and marketing, 237-258 (chap-
ter XIII).

mass-selection, 61.

Michigan, production of potatoes
in, 3.

Inde.}

317

Milward, 33.

Minnesota, production of potatoes

in, 3.
mosaic, control, 206.
Myers, 59.

net necrosis, 203.
Newman, 73.

New York, production of potatoes
in, 3.
State Potato Ass'n, score card
of, 53.
nitrate of lime, 120.
nitrogen, 119.

Norfolk, Va., as a potato center, 7.
North America, introduction into,
15.
production of potatoes in, 3.

oats, value in United States, 3.

world's crop, 1.
Orton, 73.

packages, 245.

papas, 16.

Paradisus, 16.

Parkinson, 16.

Parmentier, 18.

pedigree breeding, 62.

Penn., production of potatoes in, 3.

Peru, original home of potato, 14.

Phipps, 20.

phosphorus, 122.

picking and sorting, 232.

plant food, 94, 114.

planting, 133-142 (chapter VII).

hill and drill, 146.

tools, 148.
potassium, 123.
potato flour, 284.

plant louse, 177.

pomace, 283.

stalk wec\'il, 179.

wart, 198.
"Potatoes of Virginia," 18.

value in United States, 3.
poultry food, 283.
powdery scab, 201.
power for potato fields, 165.

price of potato land, 88.

prices, 250.

production on farms, statistics, 7.

world, 2.

in difTerent countries, 2.
pure lines, 58.

quality when cooked, 261.

Raleigh, Sir Walter, 15.

red clover in rotation, 111.

Red River Valley, as a potato

center, 7.
rhizoctoniose, 194.
rice, world's crop, 1.
Rose, 14.

rotation, 86 (chapter V).
running out of varieties, 72.
Russia, production of potatoes in,

Sacramento, Cal., as a potato

center, 7.
Salaman, 78, 82, 83, 84.
San Joaquin, Cal., as a potato

center, 7.
scab, common, 199.

powdery, 201.
score-card, 152.
seed, cutting, 156.

potatoes, 152.

treatment for scab, 153, 208.

selection, 55, 57.
shipping, 246.
silver scurf, 196.
soils, 86 (chapter V).
soil texture, 93.
Solanum Cardiophyllum, 21.

Commersonii, 21.

Jaracsii, 21.

Maglia, 21.

oxycarpum, 21.

tuberosum, 21.
sorting, 232.
South America, production of

potatoes in, 3.
Spain, introduction into, 15.
Spillman, 12, 70.
spindling sprout, 203.

318

Index

stalk borer, 180.

starch manufacture, 265.

use for, 265, 270.
stock food, use as, 280.
storage, 258.
Stuart, 27, 33, 43, 45.
sulphur, 126.
survey results, growing costs, 296.

texture of cooked potatoes, 263.
three-lined leaf-beetle, 176.
tillage, results of, 137.

tools, 135.
tip-burn, 168, 202.
tobacco, 1.

value in United States, 3.
tomato, 1.
tools, tillage, 35.
tortoise beetles, 176.
tractors, 165.

tuber-unit, method of breeding, 62.
types of potato growing, 97.

United Kingdom, production of

potatoes in, 2.
United States, production of

potatoes in, 2, 3.
yields to the acre, 12.

Uses of potato, 259-286 (chapter
XIV).

varieties of Iowa and central west,

25.
verticillium wilt, 196.

Waid's experiments, 72.
Warren, 11.

water requirements, 92.
Webber, 62.
weed killing, 140.

wheat value in United States,
3.
world's crop, 1.
white grubs, 180.
wild potatoes, 47.
Wilson, 81.
wire worms, 181.

Wisconsin, production of potatoes
in, 3.

yield, highest recorded in United

States, 12.
yields, 12, 87.

Zavitz, 71.

PItOnRTr UBRARY
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United States of America.

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