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Washington, D. C. February, 1926

RELATION OF SOIL CONDITIONS AND ORCHARD MANAGEMENT TO THE
ROSETTE OF PECAN TREES

By J. J. SKINNER, Biochemist, Office of Sovl-Feriility Investigations, and J. B.
DEMAREE, Assistant Pathologist, Office of Fruit-Disease Investigations, Bureau
of Plant Industry

CONTENTS

Page

ames LreniHienL ol Lup roseLeo Or pecan trees. - +. =... 2 222. 2s. 2 2k ie et fe i: 2
SUGGS EE TIPEROINGMR ITO fy rye ete 39 See 85 so tt 982 2: BS sb oa Se ee ae 2
aE E ET OMI ED NTS ER neg a eS ar SS Fg ns se ee a ee fi
Laboratory examination of soils from rosetted and from nonrosetted pecan orchards_-_______________ 10
UES > TALS EETE 4 a ee a eee Se ee er eee eee ee 10

we DEE ES DDS cg BES aaa a a a 13

_ Examination of the soil of good and of poor sections of orchards free from rosette_______.______-__..- 13
ESET Tlie i Ste a ee ee ee ee eee ee ee 16

The rosette of pecan trees is generally attributed by investigators
and growers to unfavorable soil conditions. Whether rosette is a
result of an unbalanced condition of nutrients in the soil, a lack of
available soil moisture, a deficiency of organic matter, or is due to
several of these factors has never been definitely determined. How-
ever, it is generally accepted that a lack of moisture and a deficiency
a soil nutrients play an important part‘ in the development of this

ease.

The relation of soil conditions to pecan rosette has received much
attention from growers and investigators. McMurran ? showed that
the evidence of rosette in badly affected pecan trees was greatly
reduced by heavy applications of stable manure. Whether the
improved condition in the appearance of the trees is due to the
additional plant food in the soil or to the greater ability of the soil
to retain moisture during droughty periods as a result of the added
organic matter is not definitely known. Further investigations by
the United States Department of Agriculture, which should throw
some light on these points, are in progress.

1 Orton, W. A., and Rand, F.V. Pecan rosette. In Jour. Agr. Research, v. 3, p. 149-174, illus. 1914.
Rand, F. V. Pecan rosette: Its histology, cytology, and relation to other chlorotic diseases. U. 8.
Dept. Agr. Bul. 1038, 42 p., illus. 1922.
is ra, S.M. Pecan rosette in relation to soil deficiencies. U.S. Dept. Agr. Bul. 756, 11 p., illus.
19.

62185—26f

2 BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE
EFFECT OF SOIL TREATMENT ON THE ROSETTE OF PECAN TREES

The first part of this bulletin reports the results of field experi-
ments which were begun in 1918 and continued until 1923 on two
prominent soil types in southern Georgia to study the effects of
ertilizers of various composition and the effect of soil conditions on
pecan rosette. No definite information as to the influence of com-
mercial fertilizers or of any particular fertilizer ingredient was
obtained, but some very interesting observations were made.
Special study was made of the relation of the amount of organic
matter in the soil to the prevalence of rosette in pecan orchards, as
early observations indicated that the organic matter of the soil had
considerable effect, either direct or indirect, on the condition of the
orchard grown thereon. In these experiments fertilizers of various
compositions and ratios were used. Phosphate, nitrogen, and potash
were used singly and in. combinations, the ratios varying in each
mixture. One of the orchards on which the work was conducted is
located near Cairo, Ga., on Norfolk fine sandy loam; the other is in
Dougherty County, Ga., on Greenville sandy loam.

NORFOLK FINE SANDY LOAM

The Norfolk fine sandy loam on which the experiment was con-
ducted consists of a gray to dark-gray fine sandy loam overlying a
friable yellow sandy clay. Two phases of this soil type occur in the
orchard, the medium phase and the deep phase. The medium phase
is underlain at about 12 inches by a yellow heavy fine sandy loam
which abruptly passes into bright-yellow friable fine sandy clay.
The deep phase differs essentially in its greater depth to the subsoil
clay. The gray loamy fine sand is underlain at 20 to 22 inches by a

ellow heavy fine sandy loam which passes into a bright-yellow clay
teen or fine sandy clay. The organic matter in this pasa is more
rapidly exhausted under cultivation than with the shallower phases.
The natural drainage of the soil is good. The mechanical analysis
of the Norfolk fine sandy loam is given in Table 1.

TABLE 1.—Mechanical analysis of Norfolk fine sandy loam from Cairo, Ga.

Constituents (per cent)

Soil material | i |
Fine | Coarse |Medfum | Fine Very fine} Silt Clay |

|. gravel |. sand | sand | sand sand
Ls Re aS 0.6 7.3 8.9 39.5| 26,1 11.1 | 6.5
Sr, oS hee el ha, = Aine al ale lctae .9 6.8 | 5.3 3775. 17.9 9.7 | 21.9
| | o

The orchard has an area of about 14 acres. It was planted in
December, 1904, to Frotscher pecan trees, and from that time to
1918 such crops as cotton, corn, peanuts; and velvet beans were
grown between the rows. About 200 pounds of commercial fertilizer,
was applied each year to the annual crops. No effort was made prior
to 1918 to increase the organic matter in the soil, and nothing was
plowed under except cotton stalks and cornstalks. Forage crops
were cut for hay. The soil at that time was not productive. The
unproductiveness was apparently the result of many years of con-

ROSETTE OF PECAN TREES 33

stant cropping to cotton and corn, with no attempt to restore the
steadily decreasing organic matter, although the soil is of a character
making it readily susceptible to improvement.

The chemical! analysis of a composite sample of soil taken from the
orchard in 1918 is given in Table 2.

TABLE 2.—Chemical analysis of Norfolk fine sandy loam }

Constituents (per cent)

Soil material Organic | N

. , Phos- + Potas- Magne-
matter | we phorus C50) sium sium
(C) | Zz | (P20s) (K20) | (MgO)
( . shi! =i tee eee 0.64} 0.031; 0.0851 0. 196 0. 228 0. 053
Sraasnireire sol) ee ter Een . 30 | . 020 . 0276 . 120 . 216 . 060
VT iPi LPS ee eee ee 22 | - 021 . 0276 . 109 . 216 . 068

1 Analysis by W. R. Leighty, O‘fice of Soil-Fertility Investigations, Bureau of Plant Industry.

The soil is very low in nitrogen and organic matter, as well as in
other plant-food constituents.

Rosette first appeared in the orchard in 1912, about the time the
trees had reached the bearing age. From 1912 to 1918 it increased
at an alarming rate, and at the end of that period the orchard was
in such a condition that its abandonment was considered.

In 1918 an experiment was begun to determine whether or not the
application of commercial fertilizers to the soil, in conjunction with
the use of green-manure crops, might bring about an improved con-
dition in the rosetted trees and increase the production of nuts. One
hundred and eight badly rosetted trees were fertilized. A number
were left unfertilized to serve as controls. Alternate trees in the
orchard were top-worked in 1919 to the Moneymaker variety, and
the others were left the original variety, Frotscher.

CULTURAL SYSTEM PRACTICED _

The cultural management of the orchard was planned so that two
cover crops a year would be grown over the entire orchard, a summer
cover crop of some leguminous plant and a winter cover crop of clover
or small grain. The entire vegetative matter produced was plowed
under to enrich the soil in organic matter. The cover crops grown
from 1918 to 1923 are recorded in Table 3.

TABLE 3.—Cover crops grown in a rosetted pecan orchard on Norfolk fine sandy
: loam at Cairo, Ga.

Year Spring and summer Fall and winter
oli ees 3 ee ee ae oe Walleye 222 ese i 2 ee ee Bur-clover.
CHG) 210 SO Ce Ee ee ee eee Cewpeds aa2= 22 = 2235 2 ook: Oats.
Ue bee. 2 ee Begparweeas 2.22 8 2 3 Rye
Lin Nn St See eee ee eee hc ee ae ee 0.
een eer ee ee SS a Velvesnedns 25 518 ou) | | Rye and oats.
ep ta eR ee ik Pee ae ee Fn ee Oe Se? as 0.

The summer crop, which was usually planted in May, was plowed
under in August or early September and the soil prepared for the
winter crop, which was planted in early October. ‘The winter cover
crop was plowed under in April and the ground prepared for the sum-
mercrop. The cost of plowing and harrowing the land in preparation

+ BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE

for planting the crop, of the seed and seeding, and the plowing under
of the vegetative matter produced by each crop on an acre basis is
given in Table 4.

TABLE 4.—Cost of growing cover crops in a pecan orchard on Norfolk fine sandy
loam from 1918 to 1923 on an acre basis }

Fall crop Summer crop
Plowing Plowing
Year under under Total
summer Seed and winter Seed and
crop and planting crop and planting
preparing preparing
seed bed seed bed

POPSe. - td Sessa c soothes J gah Sess eee $2. 00 $1.00 3.9200 [eee $5. 00
Teh ths we 8 PO et so ae Se 2. 50 1. 25 2. 50 $2. 00 8. 25
LUE SRE 8 ern ee ee en ae CO ee Ni 2. 00 1.00 2.00 1.75 6.75
D2 eee on ete oh Se eo tee 1. 50 75 1.50 1. 50 5. 25
115) OR 5 i aa ee en RCE 1.75 1.00 1.75 1. 25 5. 75
1 73) SS Se ee eee perenne ace ere 1.75 1.00 1.75 1. 50 6. 00

1 The items cover the expense of labor and team, no allowance for overhead or machinery depreciation
being included. ne
2 Cost of summer cultivation.

The cover crops improved the soil from year to year and were a
success each year. Large quantities of vegetable matter were plowed
into the soil each spring and fall. The cover crop of velvet beans

grown in the summer of 1923 is shown in Plate I. Here the luxuri-
ant growth was turned under in the fall for green manuring.

IMPROVEMENT OF THE SOIL

The soil’s organic matter and nitrogen content, which seem to be
the most important soil-fertility factors concerned, were noted
from time to time. Composite samples of soil were taken from the
orchard in 1918, 1921, 1922, and at the end of 1923 and the acidity,
nitrogen, and organic matter determined. The results are given
in Table 5.

TABLE 5.—Analyses of soil from a pecan orchard on Norfolk fine sandy loam at
Cairo, Ga.,1 in stated years

Constituents
(per cent)
Year : ee
Organic | Nitrogen .
matter (Ny
(C)?
Ree Sopcast re Se el So ee rae a 0. 64 0.031 5.4
‘I 4 LR i Re Re ERMAN I SE fie Urls MA. ho Lee 90 . 040 6.0
GOZO eee pte themi eee IF. se Le ae ge ee her il ere 1. 23 . 050 6.0
DS ee ee koe auhe oa A en Cone ee ae 1.39 . 061 5.8

1 Analyses by P. D. Boone and acidity determinations by E. F. Snyder, Office of Soil-Fertility Investi-
gations, Bureau of Plant Industry.
2To convert this carbon figure to organic matter, multiply by 1.73.

The acidity of the soil is expressed in terms of the intensity of the
acid character of the soil, technically called its P, value.

A neutral soil has a P, value of 7 and an acid soil a P, value
below 7, being increasingly more acid as the value becomes smaller.

ROSETTE OF PECAN TREES 5

The soil for the analytical work was taken from the middle of tree
rows in order to avoid as much as possible locations where fertilizers
had been applied. The large number of samples taken were com-
bined to make a composite sample representative of the entire
orchard.

The organic matter (carbon) was shown to have increased from
0.64 per cent in 1918 to 1.39 per cent in 1923, or more than double.
The nitrogen increased from 0.031 to 0.061 per cent, just about
double. The soil had an acidity (P,) value of 5.4 in 1918, 6 in
1921 and 1922, and 5.8 in 1923, which shows it had been slightly
acid, as determined by its hydrogen-ion concentration, since the be-
ginning of the experiment. Its acidity was less in 1923 than in 1918.

The physical condition of the soil has improved considerably. In
the beginning it was rather compact and became hard and baked in
the summer. As a result of growing and turning under cover crops
for six years, it is more open and porous and does not become so hard
and dry in the summer.

IMPROVEMENT IN THE CONDITION OF THE TREES

The entire orchard was very badly rosetted in 1918, and the trees
were in such poor condition that it was ready to be abandoned.
Photographs of each individual tree taken at that time and again
four years later, serve as records of the effect of the soil treatment
on the condition of the trees. Girth measurements of the trees were
taken each winter, and records of the nut yields have been made
from the beginning.

Since the limbs of badly. rosetted pecan trees die back each year
in proportion to the degree affected, the weight of dead twigs each
season was considered an important measure of the improvement or
deterioration of a badly rosetted tree. The dead wood from these
trees has been removed and weighed during May or June of each
year. These data are the most striking of all the records taken. The
comparison of photographs of the individual tree, descriptive record,
girth growth, and the dead-wood record indicate a mostdecided
improvement in the rosette condition of all the trees in the orchard
each year since 1918.

The records fail to show any relationship between the improve-
ment of the trees and the chemical fertilizers used. On the con-
trary, the controls, or trees not receiving chemical fertilizers, show
as great improvement so far as rosette is coneerned as do the fer-
tilized ones; in fact, the condition of the entire orchard has improved
in the same proportion as have the trees receiving chemical fertilizers.
The records do not show that any one chemical fertilizer or fertilizer
combination had any advantage over another when used with the
intention of curing rosette. As the improvement of the orchard
seems to be due to the general improvement of the soil by means of
growing and plowing under cover crops as practiced, the records

iven below are for a total of all the trees under observation. Records
or individual trees variously fertilized are omitted.

The condition of the orchard each year is shown in the following
tables. Records were kept of 62 Frotscher and 54 Moneymaker
pecan trees. The number of trees rosetted and the quantity of dead
wood cut from the Frotscher trees annually are given in Table 6.

6) BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE

The Moneymaker trees were budded in 1918 on the old Frotscher
stock, and there is no dead-wood record for this variety. The annual
girth growth and the yields of both the Frotscher and the Money-
maker trees are given in Table 7.

TABLE 6.—Dead wood resulting from rosette in Frotscher pecan trees grown on
Norfolk fine sandy loam soil at Cairo, Ga., from 1918 to 1928, inclusive

| Weight of dead

Number of trees wood (pounds)

Year of growth

_ Dyin NOE: «|
| Recorded| ying dying Total | Per tree

1 Trees showing no indication of rosette.

The quantity of dead wood cut from the orchard was very great in
1917, 1918, and 1919, which is a good measure of the prevalence of
rosette. This decreased greatly in 1921 and diminished to a very
small amount in 1922. In 1923 there was almost no rosette, show-
ing that the orchard had apparently overcome the disease. The
trees grew slowly prior to 1918, but made a more rapid growth
the following four years, or after the rosette began to decline.
In 1918 and prior to that year the orchard yielded few or no nuts.
The yields have increased under the treatment given the orchard,
and in 1923 the Frotscher trees yielded 576 pounds and the Money-
maker trees 530 pounds per acre.

TaBLE 7.—Annual average girth growth and yields of Frotscher and Moneymaker
pecan trees grown on Norfolk fine sandy loam at Cairo, Ga., from 1918 to 1923,
inclusive

1 Crop destroyed by insects.

ROSETTE OF PECAN TREES 7

In Plate II is shown a typical tree as it appeared in the orchard in
1918 and in 1923. A shows tree No. K-15 as it appeared in 1918
and B as the same tree appeared in 1923. The two pictures
-were taken from the same position and at the same distance. ‘The
great improvement made is well illustrated here.

GREENVILLE SANDY LOAM

A second study was conducted on another orchard, located in
Dougherty County in southern Georgia. This orchard was planted
in 1909 to a number of varieties of pecan trees, including Frotscher,
Stuart, Van Deman, and Mobile. As in the former case, chemical-
fertilizer experiments were undertaken to study the effect of various
ratios on the rosette of pecans. Applications were made in 1918,
1919, and 1920, using in the beginning 20 and later 30 pounds of
fertilizer per tree, which is equivalent in the latter case to an appli-
cation of 600 pounds per acre. ‘The same efiect was observed here
as in the experiments on the Norfolk fine sandy loam of the Cairo
orchard; that is, no beneficial results in rosette control were obtained
from any of the chemical fertilizers, nor did the cuitural system
employed in this orchard, which was quite diferent from that in the
former orchard, prove successful.

CULTURAL SYSTEM EMPLOYED

During the first eight years of the life of this orchard farm crops
of corn and cotton were grown, and little or no vegetable matter
was returned to the soil. No special attention was given to soil
improvement; even the native grasses, which produced luxuriant
crops of hay, were cut and removed from the fields. The general
method of culture of the orchard in 1918 and the four years follow-
ing has been to disk the soil very shallowly in early spring. In two
of these years peas or beans were broadcasted between the tree rows
and allowed to grow in competition with the native grasses and
weeds. In the fall the vegetation, which was usually luxuriant, was
cut and cured for hay and removed from the field. ‘The ground
was left bare during the fall and winter and a light disking made
again in the spring. At no time during the four years the orchard
was under observation was the soil plowed or put in a good condi-
tion. It became compact and hard and depleted in organic matter.
The fertilizer used in the experiment was spread on the surface and
a light disk run over the ground. There was no indication of a bene-
ficial effect of the fertilizer on the trees. However, the grass made
a better growth and produced more hay.

_In Plate III, A and B, the orchard is shown as it was in 1919 and
in 1922. The condition of the trees as well as the plan of orchard
management is seen here. The grass and peas grown during the
summer of 1919 and producing a good crop have been cut, piled,
and cured, to be removed and used for hay. The picture also shows
the scant quantity of material left on the ground. In Plate II, 8,
. the weeds and native grass grown during the summer of 1922 are
shown. It is seen that the trees have not improved since 1919, as
they are here shown to be stunted and badly rosetted.

BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE

CHARACTER OF THE SOIL

This orchard is on Greenville sandy loam, which is a reddish
brown to red sandy loam 8 to 10 inches deep. The subsoil is inva-
riably red to bright-red friable sandy loam, becoming heavier with
depth. The soil is easily cultivated, though care must be exercised
in its management, as it is liable to clod if plowed too wet or too
dry. Although the subsoil is a heavy sandy clay, no difficulty is
experienced in preparing a seed bed or maintaining a favorable
moisture content. This soil and the soil type in general have a high
agricultural value, are well adapted to and grow good crops of cot-
ton, corn, and oats, and give excellent yields of forage crops and
native grasses. Large areas of the Greenville sandy loam are planted
to pecan orchards in southern Georgia, and where properly managed
and cared for the trees are doing well. As a rule this type of soil is
considered better than the Norfolk type for general farm crops and
for pecans. The character of this sane is such that its fertility can
be more easily improved and maintained by good methods of soil
management and fertilization than the Norfolk sandy loam. The
mechanical analysis of the Greenville soil is given in Table 8.

TABLE 8.— Mechanical analysis of Greenville sandy loam from Dougherty County,
Ga.

Constituents (per cent)

| :
|

The orchard on which the chemical-fertilizer experiment was con-
ducted contained about 18 acres. The trees were 9 years of age at
the time and very badly rosetted; they produced practically no nuts.
The land had been growing general farm crops, and no vegetation
was turned under. ‘The plowing which was necessary for the annual
crops had been very shallow and the cultivation scant. However,
fair yields of farm crops were obtained, and the native grass which
was cut for hay yielded well.

In 1918, soil samples, representative of the entire 18 acres, were

taken for laboratory work, and the chemical analysis is given in
Table 9. 4

TABLE 9.—Chemical analysis of soil from a Greenville sandy loam orchard in
Dougherty County, Ga., in 1918 !

Constituents (per cent)

Soil material . | ri ¥ j

peas Nitrogen re Calcium | Potash eer a

Cy Bie. c | (CaO) | (K20)

(C) (P20s5) | (MgO)
MOI meee Pee. ee at he ie erg SE 0. 37 0. 022 0. 0407 0. 182 0. 264 0, 0598
ilustietsce Solan en ese .3l . 026 . 0230 | . 128 . 298 . 0962
STIS) ey ee eee Oe ee ENE . 29 | .018 . 0276 . 182 . 276 .1179

1 Analysis by W. R. Leighty, Office of Soil-Fertility Investigations, Bureau of Plant Industry. .

Bul. 1378, U. S. Dept. of Agriculture PLATE I|~V

A PECAN ORCHARD ON NORFOLK FINE SANDY LOAM IN WHICH COVER CROPS
OF VELVET BEANS WERE GROWN AND PLOWED UNDER FOR GREEN MANURING

62185—26,——2

PLATE

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1378, US, Dept.

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Bul. 1378, U. S. Dept. of Agriculture PLATE III

GENERAL VIEWS OF A ROSETTED ORCHARD ON GREENVILLE SANDY LOAM

A.—The practice of removing all vegetation produced in the pecan orchard is shown here. Note
the condition of these 9-year-old pecan trees, photographed in October, 1919. B.—Note the char-
acter of vegetation, consisting of weeds and native grasses grown during the summer, and the
rosetted condition of the trees. Photographed during the summer of 1922

PLATE IV

Dept. of Agriculture

1378, W.

Bul.

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PLATE V

Bul. 1378, U. S. Dept. of Agriculture

PLATE VI

1378, U. S. Dept. of Agriculture

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PLATE VII

Bul. 1378, U. S. Dept. of Agriculture

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PLATE VIII

1378, U. S. Dept. of Agriculture

Bul.

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ROSETTE OF PECAN TREES 9

The quantity of the nutrients commonly used as food by plants
-does not vary to any great extent in the Greenville and Norfolk
orchards. The sample of Greenville soil obtained in 1918 contained
less organic matter, nitrogen, and phosphorus, about the same
quantity of calcium, and slightly more potash and magnesium than
the Norfolk soil.

The structure of the soil was good; it crumbled easily, and when
lowed and harrowed it was easily pulverized. However, it became
ard and dry during the summer in times of drought.

Samples of soil collected from the orchard late in 1922, four years
after the first sampling was made, contained less nitrogen and organic
matter than the samples taken in 1918. The organic matter (carbon)
had decreased from 0.37 to 0.29 per cent and the nitrogen from 0.022
to 0.018 per cent. These differences, though slight, tend to show that
the soil was losing in the properties which determine fertility and
-crop-producing power under the cultural system practiced.

CONDITION OF THE TREES

The orchard under observation was in a very poor condition and

badly rosetted in 1918. The trees had been in bad condition for two

years prior to this date. At the time that they should have begun
to produce nuts, rosette appeared and grew steadily worse. This
was true of every variety, none escaping the disease.

A record of 107 trees in the 18-acre orchard was kept. Photo-
graphs were made in 1918 and the trees photographed again in 1922.

irth measurements to determine the growth of the trees were taken
annually, and the quantity of dead wood resulting from rosette was
recorded each year.

The dead wood in the 107 trees weighed 453 pounds in 1917, or
4.23 pounds per tree. In 1918 there were 845.5 pounds of rosetted
wood, averaging 7.9 pounds per tree. These records were not made
in subsequent years.

The average girth growth of the 107 trees was five-eighths inch
in 1918 and 1 inch in 1919. The yields in 1918 for the 107 trees
totaled about 3.5 pounds of nuts. In 1919 less than 1 pound was
harvested, and in 1920 only a few trees bore, the yield being very
small. The trees have been in very poor condition since that time
and have produced very little. The orchard was practically aban-
doned by 1923.

A photograph of a typical tree in this orchard is shown in Plate
IV, A and B. -It was taken in the summer of 1918 soon after the
experiments were begun. The rosetted condition of this tree should
be specially noted and compared with its condition four years later,
as shown in the photograph taken in the late summer of 1922. In
each case the trees were photographed from practically the same
position and at the same distance. The trunk has increased in girth
Measurement, but the top has died back each year, and the condi-
tion of the tree appears hopeless.

10 BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE

LABORATORY EXAMINATION OF SOILS FROM ROSETTED AND FROM:
NONROSETTED PECAN ORCHARDS

The relation between the rosette, the character of tree growth,.
and the productiveness of pecan trees and soil conditions has been
investigated in a number of orchards, and the results are given
in this bulletin. a

It was found that there is a close correlation of high nitrogen and
organic-matter content of soil with productive trees free from rosette
and of low nitrogen and organic-matter content with nonbearing
rosetted trees. In orchards free from rosette there was invariably
a correlation of high nitrogen and organic-matter content of soil
with thrifty, productive trees and of low nitrogen and organic-matter
content with feeble growth and minimum productiveness. The re-
sults indicate that it is immaterial whether the increased organic
matter in the soil is brought about by the use of cover crops or the
addition of stable manure or is caused by a natural accumulation of
litter and débris.

ORCHARD SOILS EXAMINED

The relation of soil conditions to the rosette of pecan trees was
investigated in 11 orchards in southern Georgia, northern Florida,
and Alabama. The soils of these orchards were examined, because
in each it was possible to find under the same management both
rosetted and healthy trees of uniform age and variety growing on
uniform soil types. In each orchard samples of soils were obtained
from a rosetted and from a healthy section of the orchard. Records
were made as to the subsoil conditions of the two sections and of
the cultural system practiced. In each case soil samples were taken
for laboratory determination of their acidity, nitrogen, and organic--
matter content. Comparisons were thus made between the soils of
rosetted and healthy orchards. The data for the soils of these 11
orchards are given in Table 10.

ORGANIC MATTER

The organic matter of the soils in 9 of the 11 orchards in which
these investigations were conducted was greater in the soil from the:
normal sections than in that from the rosetted sections. In orchards
Nos. 3 and 5 the organic matter was greater in the soil from the
diseased than from that in the healthy sections. The subsoil was
probably responsible, at least in part, for the condition of the trees.
in the diseased sections of these orchards.

Wide variation was found in the organic matter content in the
soils of these 11 orchards. In reading these tables, comparison
should only be made between the soil from diseased and from healthy
sections of individual orchards and not between soils from different
orchards, as the data are not presented to show the amount of organic
matter necessary for healthy pecan trees. The humus requirement
necessarily varies with different soils, and the data resulting from this
work are insufficient to determine that question. They do, however,.
indicate that the percentage of organic matter in a soil is an important.
factor in causing or preventing pecan rosette.

i ROSETTE OF PECAN TREES +k
NITROGEN

The nitrogen content of soil from healthy sections of each orchard
is greater than that from the rosetted sections in 7 cases of the 11
examined. Even where the reverse is the case, the nitrogen content
of both soils is very nearly the same. The ratio of nitrogen to
organic matter is not exactly the same in any two samples of soil.

ACIDITY

All of the soils examined, except one, were found to be acid in re-
action. The acidity is given in terms of P, values which were
determined by the hydrogen-electrode method. There is no apparent
relation between the degree of acidity of the soil and the quantity
of pecan rosette in the orchards examined. In seven of these orchards
the soil from the rosetted sections was found to be slightly more
acid than that from the healthy sections, in one orchard the degree
of acidity was the same in both soils, and in three the acidity was
less. There was no wide variation in the degree of acidity in any of
these soils except in orchards Nos. 2, 6, and 11, and from the data

rocured it would seem that a slight degree of acidity is not a factor
In causing rosette.

In orchard No. 2 the soil from the rosetted section was less acid
than that from the unrosetted section. The acidity (P,) value was
5.7 and 4.2, respectively. In orchard No. 6 the soil from the rosetted
section was alkaline, having a P, value of 7.7, and that from the
healthy section was slightly acid, having an acidity (P,,) value of 6.1.
On the other hand, in orchard No. 11 the soil from the rosetted sec-
tion was more acid than that from the healthy section, the acidity
(P,) value being 5.4 and 6.1, respectively. There is nothing in these
data to show that there is any relation between slight degrees of
acidity and rosette.

ORCHARD CULTURE
f

The growing of leruminous cover crops for green manuring or the
application of stable manure has been responsible for the greater
organic-matter content of the soil in the healthy sections of most of
the orchards examined.

CONDITION OF THE SUBSOIL

. The unfavorable character of the subsoil is evidently an important

factor in causing rosette of pecan trees, but only a few cases in the 11
orchards examined permit study of this factor. In orchard No. 3
the subsoil from the diseased section was very stiff and hard, which
was not the case in the healthy sections and was probably the prin-
cipal factor in the cause of the rosette. It was also a possible factor
in orchard No. 7, where the subsoil was stiffer and harder in the dis-
eased than in the healthy section. The rosetted condition of a sec-
tion of orchard No. 5 may be due to the deeper and more porous
nature of the subsoil. In the other orchards mentioned in Table 10
the subsoil conditions were similar in the rosetted and healthy sec-
tions.

BULLETIN 1378, U. S. DEPARTMENT OF AGRICULTURE

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ROSETTE OF PECAN TREES 13

DISCUSSION

In orchards affected with rosette the turning under of leguminous
crops has proved a highly successful remedy. It is attended by an
increased organic-matter content of the soils, which not only furnishes
a steady and gradual supply of nitrogen for the trees but improves
the physical condition of the soil and increases its moisture-holding
capacity. The data procured in the orchards investigated show a
close relation between the humus content of the soil and the rosette
of pecans. As the organic matter in the soil increased, the rosette of
the orchards decreased and gradually disappeared.

Methods of increasing the humus content of a soil vary, but an

easy and inexpensive way is by the use of green-manure crops. The
application of large quantities of stable manure would probably give
the quickest results, but stable manure is expensive and difficult to
obtain. The natural growth of grass and weeds allowed to decompose
on the ground would likely help somewhat. Applications of ordinary
- commercial fertilizers alone apparently do not serve as a remedy for
_ the rosette of pecans.
This statement seems applicable also to the rosette of apples.
_ Morris,’ working with apples on western soils, obtained no apparent
improvement with apple rosette by the application of chemical fer-
tilizer, but orchards in which leguminous cover crops were grown out-
_ grew the diseased condition in three to five years. The practice of good
arming methods which maintain a high degree of soil fertility is as
_ essential to successful pecan growing on upland soils as it is in the
_ growing of any farm crop. Fertile soil is necessary to develop nor-
mal, healthy trees capable of producing good crops of pecans.

In order to determine the relation of the organic matter of the soil
to the general growth of pecan trees and the production of nuts, other
rosette-free orchards were examined. ‘The data are given below.

EXAMINATION OF THE SOIL OF GOOD AND OF POOR SECTIONS
OF ORCHARDS FREE FROM ROSETTE

The soils of eight orchards containing no rosette in which different
cultural methods had been practiced were analyzed for nitrogen and
organic matter and their acidity determined, so as to ascertain the
relation of these factors to the condition of the orchards. In these
orchards, each having a uniform soil type, two cultural methods had
been practiced. Each presented an opportunity to study the effect
of soil and orchard management or fertilization on the soil and on
pecan growth and yield.

The soils examined were from orchards situated in Georgia, Florida,
and Alabama and are reported as being well adapted to pecan culture.
The soil samples were collected in 1921 and 1922, and the orchard
record was made at that time. The data are given in Table 11.

Comparisons should be made between the two sections under
different cultural treatments in each orchard (Table 11). The soil
types and also the tree varieties in each section of each orchard were
the same. The differences shown in tree growth and yield are
apparently due to cultural treatment. The effect of the soil treatment
on the organic matter and nitrogen of the soil is striking, and invari-
ably the greater organic matter and nitrogen content are correlated
with good tree growth and yield.

# Morris, O. M. Apple rosette. Wash. Agr. Exp. Sta. Bul. 177, 30 p., illus. 1923.

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ROSETTE OF PECAN TREES 15

The data shown for orchard No. 1 are interesting. The entire
orchard was fertilized with chemical fertilizer. One section of the
orchard, on which asparagus was grown, was cultivated in the
spring and no further attention given the soil during the year. In
the other section corn was grown on strips 15 or 20 feet wide between
the tree rows, and the remainder of the ground was seeded to cow-
peas annually. A stunted tree growth resulted where asparagus
was grown; these trees came into bearing late, and the yield was
small; and the soil was found to contain much less nitrogen and
organic matter. Results similar to these are frequently seen where
nursery stock is grown in a portion of a pecan orchard, a practice
which frequently has a detrimental effect on growth and produc-
tiveness.

The results of improving the soil and putting it in a high state of
fertility before planting the orchard are shown in orchard No. 2.
Previous to setting this land to pecan trees, one section had been
well cultivated and its fertility carefully maintained. The other sec-
tion was poorly farmed for years, and as a result it was In an im-
poverished condition. ‘The growth of the pecan trees during the first
‘seven years after the orchard was planted was considerably better on
the good farm than on the poor one, even though the trees on
both farms received the same cultural treatment. The general ap-
pearance of the trees on the farm which was well tilled previous to
planting is shown in Plate V and that of those on the farm poorly
tilled previous to planting in Plate VI. The nitrogen and organic
matter of the soil at the time the sampie was taken in 1921 were
much higher in the soil from the good farm than from the poor one.

The results of growing cover crops for green manuring as compared
‘with no cover crops and no cultivation are shown in orchard No. 3.
The trees in the cultivated sections during their first four years of
growth had developed a great deal more rapidly than the others.
The soil was found to contain 1.11 per cent of organic matter (C)
as compared with 0.77 per cent for the uncultivated section. The
nitrogen content was also higher.

It is frequently observed that pecan trees growing beside a fence
or a ditch bordering an orchard develop more rapidly and yield
better than do trees in the orchard adjoining, even though the latter
may be well tilled. Illustrations of this were afforded by orchards
Nos. 4 and 5. In both cases the two were thrifty and good yielders,
but trees adjacent to the fence and ditch were much larger and
yielded nearly twice as many nuts. Ordinarily considerable débris
accumulates near a fence or ditch and appears to be the cause of
improved tree growth. The organic matter and nitrogen were
found to be more than twice as great in the soil near the fence and
ditch as in adjoining fields. It is also frequently observed that
pecan trees in or near barnyards or dwellings do much better than
trees in adjoining orchards. Illustrations of this are given in orchards
Nos. 6, 7, and 8. The trees in orchard No. 7 are shown in Plate
VII, A being a large tree near a chicken house and B a typical tree
in a field adjacent to the yard. A great difference is shown in the
size of the two trees. The trees in orchard No. 8 are shown in Plate
VIII, in which A is typical of the trees in the field and B shows the
tree near the dwelling, photographed at the same distance. The
latter was a much larger tree and a heavier yielder. The organic

16 BULLETIN 1378, U. S. DEPT. OF AGRICULTURE

matter and nitrogen in the soils under trees growing in the yards:
near dwellings were much greater than in the adjoiming orchards,
and the nut yields were correspondingly greater. All of these soils,
as shown by hydrogen-ion exponents, were slightly acid, but prac-
tically no difference was found between the degree of acidity of the
soils producing large and small crops of pecans.

SUMMARY

Two badly rosetted orchards grown on soils low in both organic
matter and fertility were subjected to different cultural treatments,
one of which included plowing, thorough cultivation, and the grow-
ing and turning under of two green-manure crops each year; the
second included only a light disking annually and the growing of
grasses and weeds with no plowing. In the latter case, the vegetation
produced was cut and removed as hay and none turned under.
Chemical fertilizers, as used in the experiments, had no influence in
decreasing or increasing rosette.

The former treatment was coincident with an increase in the supply
of organic matter and nitrogen in the soil, which resulted in a gradual
improvement and finally in the apparently complete disappearance
of all rosette symptoms on the trees and a return to a normal pro-
duction of nuts. On the other hand, the second cultural treatment
was coincident with a decrease of organic matter and of nitrogen in
the soil and a marked increase of rosette symptoms, resulting in the
abandonment of the orchard.

Soils from healthy and rosetted sections of pecan orchards of uni-
form soil type and of uniform tree age and variety were examined
in the field and laboratory. There is a close correlation in these
orchard soils having a high nitrogen and organic-matter content with
healthy productive trees and of soils having a low nitrogen and
organic-matter content with unfruitful rosetted trees. There was no
correlation of soil acidity with good or poor pecan orchards.

In orchards free from rosette there is a correlation of high nitrogen
and organic-matter content of soil with productive trees and of a
low nitrogen and organic-matter content with poor tree growth and
poor nut yield.

It is apparent that the accumulation of organic matter in the soils,
whether acquired by the growing and plowing under of cover crops
or by the addition of manures, composts, or débris, is beneficial to
pecan trees and stimulates increased growth and yield.

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Full text of "Relation of soil conditions and orchard management to the rosette of pecan trees"

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