MataLib.

Agric. Dept.

United States

BUREAU OF SOILS— CIRCULAR No. 15.
MILTON WHITNEY, Chief of Bureau.

MANURIAL REQUIREMENTS OF THE LEONARDTOWN LOAM SOIL OF
ST. MARY COUNTY, MD.

The Leonardtown loam is the most extensive soil type in St. Mary
County, Md., and is locally known as the " white oak " or " kettle
bottom " soil of the upland. Excepting the Norfolk loam, it lies at
a higher altitude than any of the soils of the county. The surface is
usually gently rolling. Extensive forests of white oak and pitch
pine are found largely on this type of soil.

The crops to which it is best adapted are wheat, corn, and grass,
although tobacco is frequently grown in rotation with these. Its
crop-producing power varies greatly, this variation being due chiefly
to the different treatment to which the soil has been subjected in dif-
ferent places. When well managed it produces good yields of the
crops above mentioned.

The soil is a light-colored silt loam, containing from 8 to 20 per
cent of clay and from 50 to 60 per cent of silt. It is usually free
from gravel and contains very little coarse or medium sand, with a
considerable percentage of very fine sand. It is rather low in
organic content. If worked when too wet, the soil has a tendency to
puddle, and upon drying bakes into a hard mass. This tendency
can be largely overcome by the application of lime or of organic
matter. The subsoil consists of a mass of clay lenses, lumps, and
fragments, separated from each other by seams or pockets of sand.
This peculiar structure causes it to behave much like a dense clay as
regards the circulation of water.

The geographical position of St. Mary County as regards the great
markets of the East and its favorable climate for agricultural opera-
tions are natural conditions justifying the best of agricultural prac-
tices. The rotation usually followed in St. Mary County is tobacco,
corn, wheat, and grass, or sometimes a season of fallowing.

As the Leonardtown loam is not well adapted to the growing of a
quality of tobacco which buyers expect from that county, and as
tobacco is the great money crop of the locality, this has led to the
abandonment of considerable areas of the type to forest occupation.

29738— No. 15—05

SAMPLES COLLECTED.

During the summer of 1904 a party was sent to Leonardtown to
carry on investigations on different phases of the Leonardtown loam
and to ascertain if the wire-basket method which had recently been
devised for a study of the fertility of soils was sufficiently perfected
to make it of practical use. The results obtained during the summer
demonstrated that the method was capable of showing the same order
in the crop-producing power of the soils as was observed in the field,
and that it was also useful in determining Avhat fertilizing materials
would give the best returns. The facts gathered during the summer
were thoroughly in accord with what had been previously observed
in making a soil survey of this county and also with the experience
of the more progressive farmers.

In 1905 samples wrere taken from two phases of the Leonardtown
loam. The sample designated " good " was taken from a field in a
high state of cultivation located within the borders of Leonardtown.
For quite a number of years this field had received annually liberal
applications of stable manure. It was then put dowrn to grass and
remained for five or six years, when the grass ran out. In the spring
of 1903 the field was plowed and planted to corn without the appli-
cation of manure or any kind of fertilizer. The result was a fine
crop of corn, estimated at about 80 bushels per acre. The following
year, 1904, it was again plowed and planted to corn without fertilizer,
but there was a marked falling off in the crop, which may have been
caused by one or all of three conditions, namely, poor cultivation,
shortage in rainfall, or the fact that the same crop had been grown
the preceding year.

The other large sample of soil, designated as Leonardtown loam
" poor," was taken from a field several miles distant from Leonard-
town, and although it had been owned by the same man for more than
twenty years he had always rented the place and knew very little
as regards its past treatment. The tenants were not permanent, and
very little information could be gained from that source. The land
was considered in the neighborhood as very unproductive, and this
statement is further emphasized by the fact that the entire tract of
something over 100 acres brought the owner an annual rental of only
$50. In 1902 it was occupied by a colored tenant. The following
year it was unoccupied and uncultivated. In 1904 it was again cul-
tivated, and in the field where the sample was taken corn averaged!
about 2 feet in height and produced practically no grain.

The chief differences in the appearance of these two soils in the
field is that the poor one is somewhat lighter in color, contains less
organic matter, and is much more compact and difficult to cultivate.
In texture it may contain slightly more silt than the good sample,

but this difference is very slight and not sufficient to account for the
great difference in yield; in fact, certain beneficial treatments given
the poor soil by the wire-basket method have caused it to outrank the
good soil by any treatment yet tried.

It must be understood that the results of the following investiga-
tions are held to apply only to the two fields under consideration,
although it seems probable from a study of the conditions throughout
'the county that they might be applicable to considerable areas of this
type of soil. It must be understood, also, that the conditions encoun-
tered in field practice are so different from those which obtain in
these experiments that the treatments, if put to a practical field test,
might prove more or less efficient, or, owing to uncontrollable condi-
tions, such as excessive rainfall or drought, might fail entirely.
Furthermore, the wheat plant has been used exclusively as the test of
fertility in these experiments, and whether this plant is a safe indi-
cator of the manurial requirements of other crops is a matter which
has not yet been determined. It is, however, generally conceded that
if a soil can be made productive for wheat, it will be productive, as a
rule, for general farm crops. The object herein aimed at is to secure
a larger crop, regardless of difference in quality or texture ; that is, to
change the soil conditions in such a way as to enable it to produce
more vegetable matter.

WIRE-BASKET METHOD OF DETERMINING MANURIAL REQUIREMENTS.

The two large samples of soil collected were each subjected to
various treatments, and the effect of the treatments ascertained by
growing an equal number of wheat plants on each for a period of
about twent}7-five days, or as long as favorable growth could be main-
tained on the limited amount of soil used for the number of plants
that were grown. The method of growing the plants is as follows:

Five small wire baskets 3 inches in diameter by 3£ inches in depth
are used for each treatment. After the soil has been treated with
its respective fertilizer and brought up to the optimum water con-
tent with distilled water, the equivalent of about 325 grams of dry
soil is placed in each basket. The soil is firmly packed, and six
germinated kernels of wheat are planted in each basket. During
the process of packing a small portion of the soil presses out through
the wire mesh, but this is brushed off and returned to the interior of
the basket, after which the basket is at once dipped into melted par-
affin, which not only forms an intimate contact with the soil, but also
produces a water-tight covering. An eighth to a quarter of an inch
of washed quartz sand is now placed over the soil of each basket and
its contents at once weighed and the weight recorded. In from three
to five days the wheat plants will have emerged from the soil and

have a height of approximately 1 inch, at which time the surface of
the basket is sealed — that is, it is covered with a piece of paper hav-
ing a small opening in the center sufficiently large to permit the
plants to pass through. The paper is dipped in melted paraffin just
before placing it over the soil, and then a small amount of paraffin
is run around the outer edge of the paper, thus forming contact with
the side of the basket. In this way all evaporation from the soil is
prevented, excepting the minute amount which may pass through
the small opening immediately around the plants. The loss from this
source is so slight in comparison to that which is transpired by the
plants that no account is taken of it, but even if the loss were consid-
erable it should be practically the same from all baskets. The weight
of the basket is taken immediately before sealing and immediately
afterwards in order to ascertain the weight which has been added to
it in the process of sealing. This increase is now added to the orig-
inal weight of the basket, and the result is what is known as the
u optimum weight," or that weight at which the contents of the
basket contain the most favorable amount of moisture for the growth
of plants.

During the growing of the plants, which usually continues from
eighteen to twenty-one days from the date of sealing, the baskets
are weighed at intervals of two or three days and watered with
distilled water in order to retain a favorable moisture content
for plant growth. By this method the loss of water or the amount
transpired by the plants is ascertained periodically, and at the end
of the experiment the total amount of water given off through the
plants of each basket is obtained for comparison with the growth
and green weight of the plants, which is ascertained by cutting and
weighing the plants at the time the experiment is concluded. All
conditions of the experiment are so carefully controlled that the
average result of five baskets rarely differs more than 5 per cent
from the average result of any other five baskets that have been
treated throughout in precisely the same manner. Differences which
occur beyond this amount may therefore safely be attributed to the
different manurial treatments which have been given. This method
has several advantages over the growing of plants in open and porous
pots. The method of coating the baskets with paraffin prevents any
accumulation of roots between the soil and receptacle, a trouble which
is so common in pot experiments. The complete sealing up of the
soil also enables the experimenter to determine the amount of water
which the plant has actually used and transpired in its process of
growth, and this, together with the small size of the baskets, enables
the moisture content and its fluctuations to be carefully controlled.
When the plants have attained considerable size, the draft made
upon the soil moisture is very great, and on warm days with bright

sunshine the plants may use half of the moisture which the soil
contains. The draft upon the soil that occurs during this period of
growth, both as to moisture and mineral-food constituents, is prob-
ably as great as that under field conditions by the removal of a large
mature crop, providing we assume that the removal takes place to
no greater depth than 1 foot, which, in the case of wheat and other
similar crops, would be approximately correct. For example, the
amount of green matter in the plants of the untreated poor Leonard-
town loam soil was at the rate of 12,000 pounds to the acre-foot, and
the water removed was equal to 20 per cent of the weight of the soil,
or the equivalent of 3.1 inches of rainfall.

A large number of moisture determinations show that the wheat
plants at the time of cutting from the baskets contain about 85 per
cent of water. On this basis the air-dry matter produced in the tops
of the plants would be equal to 2,000 pounds per acre. In case of a
mature crop of wheat we know that the straw and the thrashed grain
are about equal in weight, and on this basis the above amount of mate-
rial removed from the soil is equivalent to a crop of about 16 bushels
of wheat per acre, or far more than would probably be obtained in
practice on the field from which this sample was taken, especially
when untreated.

Another portion of the same sample of soil when given a liberal
application of barnyard manure, nitrate of soda, sulphate of potash,
and acid phosphate produced a yield of green matter equal to 32,300
pounds per acre-foot of soil, and the plants used an amount of water
equal to 44 per cent of the weight of the soil, or the equivalent of
about 7 inches of rainfall. By computation as above this would be
equal to 45 bushels of wheat per acre, or a crop which on Leonard-
town loam soil would be considered unusually large, although per-
haps not beyond what has occasionally been obtained under most
favorable conditions in field practice.

In the case of the sample of good soil the yield from the untreated
was 50 per cent greater than that from the poor, or the equivalent of
24 bushels of wheat per acre. The difference is not so great as
might be expected, judging from the crop-yielding power of the two
soils as observed in the field. In case of the poor soil, however, the
above-estimated yield of 16 bushels per acre for the untreated portion
is probably far greater than would have been obtained under field
conditions, and has probably arisen from the fact that the mechan-

il condition of the soil has been very greatly improved as used in
basket experiments, and nearly the optimum amount of water has
all times been maintained. From the above data it will be seen,
lerefore, that by this method of cropping the draft made upon the
>il within the short period of twenty -five daj's is fully as great, if
greater, than that made in field practice during the whole season.

This is further substantiated by the fact that when the soil in these
baskets is immediately replanted with wheat there is a decline in the
growth of the second crop of 50 per cent, especially where the soil
is untreated. With certain beneficial treatments, however, or by
re-treating the soil just before planting the yield may be maintained.

RESULTS OF DIFFERENT MANURIAL TREATMENTS OF LEONARDTOAVN LOAM.

In view of the fact that this soil is apparently deficient in organic
matter, it was believed that treatments with barnyard manure would
be especially beneficial. All practical farmers are of course aware
of the fact that there is considerable variation in the composition
of barnyard manure, and that its efficiency also depends upon its
state of decomposition. In order to get some results bearing upon
these points samples of manure Avere obtained from eight different
sources, and the above two samples of soil, as well as others, were
treated with these manures at the rate of 20 tons per acre.

The following table shows the results of the experiment, the rela-
tive growth of plants being expressed on the basis of 100 for the
untreated soil in each case :

Kffcct of manure from, different sources on Leonanltotcn loam.

Kind and source of manure.

Relative growth
on —

Poor
soil.

Good
soil.

Untreated soil .

a ICO
175
173
158
155
154
131
110
81

a 100
139
125
131
120
142
123
115
88

Rotten manure from propagating gardens

MftTitirf* fvr>m Tafrorna Park

Oow manure fresh from pasture

Decayed organic matter from city dump .

Horse manure from city dump

Rntl-fvn manure from Department, greenhouse

Horse manure, fresh .

a In this and subsequent tables the actual relative growth on the untreated samples of
these two soils is 100 for the poor and 148 for the good, but the results of each treatment
are stated on the basis of 100 for the untreated soil to simplify the comparison of the
different treatments.

The above results show that the efficiency of barnyard manure on
these soils is widely variable and that under certain conditions of tht
soil or of the decomposition of the manure it may actually be harmful.
The depressing effect of the sample of fresh horse manure can not
attributed to its lack of plant food constituents, for it was probably
one of the most concentrated in the series. It seems likely that some
product in the manure or the decomposition which took place ii
the soil gave rise to products that were somewhat injurious to the
plants. It is noticeable throughout the experiment with barnyai

manure that the poor soil responds to a much greater degree than the
good one, the maximum increase attributable to manure being about
75 per cent. As a result of many experiments with these two sam-
ples of soil where manure has entered into the treatment in amounts
ranging from 2£ to 20 tons per acre it has been found that the small
amounts give relatively larger increases than the larger amounts,
and it suggests the probability that applications of barnyard manure
in field practice will be most economical if applied at the rate of
about 10 tons per acre.

EFFECT OF LIME.

Lime having proven decidedly beneficial, especially on the poor
soil, it was applied in different amounts ranging from 1,000 to
8,000 pounds per acre, the rate of application being based on the cal-
culated weight of an acre of soil to a depth of 7 inches, wrhich is
approximately 2,000,000 pounds. The following table shows the rela-
tive increase in growth attributable to the different applications of
lime as compared with the untreated soil, which is taken as 100 in
each case:

Effect of lime on Lconardtown loam.

Liine per acre.

Relative growth
on —

Poor
soil.

Good
soil.

Untreated soil

100
138
140
136
137
135

100
111
112
110
108
119

1,< M (pounds

2,000pounds

4.000 pounds ._

6,000pound.s

S.OOO pounds

The lime above used was air slaked. It will be noticed that its
effect is relatively much greater on the poor soil than it is on the good
one, and that there seems to be no appreciable increase for applica-
tions greater than 1,000 pounds per acre. In other words, the lime
requirements of the soil seem to be fully met by applications of 1,000
pounds, but there is apparently no harmful effect even where the
amount is 8,000 pounds per acre. It is possible that in subsequent
'•rops the larger amounts may have a residual effect greater than the
smaller application, but it would seem wiser to give small applica-
tions at frequent intervals rather than large applications with the
expectation to have the results extend over a long period of time.
In another experiment where lime was applied at the rate of 6,000
pounds per acre and three successive crops grown without re-treat-
ment, the yield for lime was 130, 213, and 112 for the first, second,
and third crops, respectively, as compared with 100 for each of the
three successive crops grown on the untreated soil, or a mean gain

8

for the three crops of 46 per cent. Lime always gives an increase in
growth on Leonardtown loam, poor, no matter whether used alone or
in combination with barnyard manure, chemical fertilizers, or green
manure. Its most pronounced effect, however, was where it has been
used in connection with barnyard manure. In this instance manure
was used with' and without lime, the former at the rate of 10 tons
per acre and the latter at the rate of 2,000 pounds per acre. Foul-
successive crops of seedling wheat were grown without re-treatment
of the soil. In the first crop manure gave an increase of 14 per cent,
and manure and lime together gave an increase of 93 per cent, or an
increase attributed to the lime of 79 per cent. The succeeding crops
showed a marked diminution in growth for both the treated and un-
treated soil, the diminution being equally as great in the manure-
treated soil as in that which was untreated, but much less marked in
the case where lime was applied with the manure. The results of the
four crops showed an aggregate increase attributable to the lime equiv-
alent to 26^ bushels of wheat. If results approximating these can
be obtained in field practice, it is plain that the application of lime
at the rate of a ton per acre as above used would be an exceedingly
profitable treatment, especially in view of the fact that where lime
is obtainable near by its cost should not exceed $3 per ton. It is
not at all improbable, however, in this case that the application of the
lime in conjunction with the manure has rendered the manure more
effective. This seems most likely because the lime in this instance
has been about twice as effective as when used alone, and, further-
more, the manure used without lime has had very little permanent
effect, the application of 10 tons producing an aggregate increase in
yield for the four crops equivalent to a little less than 5 bushels of
wheat, the main effect showing in the first crop.

EFFECT OF CHEMICAL FERTILIZERS.

Nitrate of soda', sulphate of potash, and tricalcium phosphate have
been used in numerous instances alone, in combination with each
other, and in various combinations with manure, lime, and both
manure and lime. Nitrate of soda and sulphate of potash have been
used in amounts approximately 250 and 500 pounds per acre each,
while tricalcium phosphate has been used at the rate of 150 and 300
pounds per acre. Nitrate of soda, whether used alone or in combina-
tion with other constituents, has usually given an increase in growth
except where lime enters into the combination. In the presence of
lime, nitrate of soda invariably either gives no increase or produces
a slight decrease in the effect of the lime alone. Its beneficial effects
are most pronounced where used in combination with barnyard ma-
nure. In the experiment above referred to under the heading of lime.
where four successive crops were grown without re-treating the soil.

nitrate of soda was used at the rate of 500 pounds per acre in connec-
tion with an application of 10 tons of manure. In the first crop it
produced an increase in growth amounting to 49 per cent over the
manure alone, but had practically no residual effect, for the baskets
treated with barnyard manure alone in the two following periods gave
equally as large returns as did those which had been treated also with
nitrate of soda.

Sulphate of potash is also beneficial on this soil, especially where
used in combination with manure, and in the above-mentioned ex-
periment, where used at the rate of 500 pounds per acre in connection
with manure and nitrate of soda, the increase attributable to the
potash amounts to 31 per cent. It is quite noticeable, also, that this
effect has been felt in the subsequent crop, and, in fact, the aggregate
increase attributable to the potash salts, when used in combination
with manure, for the four crops is equal to 28 per cent. Tricalcium
phosphate, on the other hand, has rarely given any increase in
growth. There is some question, however, as to whether this con-
stituent could be expected to show its effect in the early growth of
the wheat plant. It is quite possible that its effect might become
beneficial to the final growth of the plants.

The following figures show the comparatively small increase from
applications of nitrate of soda, potassium sulphate, tricalcium phos-
phate, or a combination of two or all of these substances when used
without manure or lime. The plant-food constituents added to the
>oil by this treatment supply certainly an adequate amount for the
needs of the crops, and the small relative increase due to their use
indicates very clearly that the cause of the infertility of the Leonard-
town loam, poor, is not due to a lack of plant food, but is due to some
other unfavorable condition in the soil.

Effect of different mineral fertilisers on Leonardtown loam, poor.

Treatments, pounds per acre.

Relative
growth.

Untreated soil

100

Sni.liiini nitrate, 230 pounds + tricalciuru phosphate, 150 pounds + potassium sulphate,
250 pounds

121

Potassium sulphate, 250 pounds

115

Sodium nitrate, 250 pounds 4- potassium sulphate, 250 pounds

111

Sodium nitrate, 250 pounds

107

Sodium nitrate, 250 pounds + tricalcium phosphate, 150 pounds

100

Tricalcium phosphate, 150 pounds . _ .

92

EFFECT OF GREEX MANURE.

The green manure applied in this case was cowpeas cut in the
early stages of growth. The peas were run through a mill and inti-
mately mixed with the soil at the rate of 9.000 pounds of the water-
free substance per million of soil, or an equivalent of 9 tons per acre.

10

The green cowpeas contained at the time of cutting 90 per cent of
water. For a few days after the plants came up the treatment seemed
to be slightly harmful. In a short time, however, the plants recov-
ered and began a renewed growth, making an increase of 89 per cent
over the untreated soil. Both the untreated and treated soils were
replanted three times, thus producing four successive crops. In the
second crop the comparative yield of the untreated and treated soils
was 100 and 650, respectively, or a gain of 550 per cent for the treated
soil. It is also worthy of note that while the untreated soil produced
only one-third as much as it did the first time, the treated soil pro-
duced more than it did the first time, whereas a crop grown on a fresh
sample of the same soil yielded approximately the same amount as the
first crop of the above untreated sample. In the third crop the rela-
tion of the untreated and treated soil was 100 and 293, respectively,
and for the fourth crop 100 and 288. The fourth crop on the treated
soil was slightly greater than the first crop on the untreated soil,
which shows that the treatment had lasted through four successive
crops of wheat without permitting the yield to go below what it orig-
inally was on the untreated soil and without re-treatment with the
green manure. The aggregate increase produced by this treatment
was equivalent to 55.000 pounds of green matter per acre, or 70
bushels of wheat for the four crops.

Both the treated and untreated soils were now re-treated with cow-
peas'at the rate of 5,000 parts per million of dry matter, or the equiva-
lent of 5 tons per acre, and replanted to wheat for the fifth time.
The yield from each of the soils was greater than any of the yields
from the previous treatment and was the largest for the sample
which had grown poor crops without any treatment, the yield being
at the rate of 45 bushels per acre.

The following table gives the relative growth for various treat-
ments which have proven decidedly beneficial on the Leonardtown
loam, poor :

ReJatirc (iroirtlt for various treatments on Lconanltoicn loam, poor.

Treatments, pounds per acre.

Relative
growth.

Untreated

Manure, 20 tons + lime, 6,000 pounds + sodium nitrate, 500 pounds + potassium sul-
phate, 500 pounds .--

Manure, 10 tons + sodium nitrate, 500 pounds + potassium sulphate, 500 pounds

Manure, 10 tons + lime, 2,000 pounds

Cowpeas, 9 tons

Manure, good quality, 20 tons

Cowpeas, 2i tons + lime, 1,000 pounds

Manure, poor quality, 10 tons + sodium nitrate, 500 pounds

Lime, 1,000 pounds 4- potassium sulphate, 200 pounds

Cowpeas, 5 tons

Lime, 2,000 pounds

Cowpeas, 2i tons

100

230

195
193
189
1T«
17-J
103
143
145
140
138

11

From the foregoing data it is obvious that both barnyard manure
and green manure are beneficial to this soil when in a run-down
•condition, but that the effects from applications of green manure
are decidedly more beneficial in that they are more lasting than for
pqual amounts of barnyard manure. The benefits from liming are
feo obvious that they need no comment, while potash and nitrogen
in combination with manure are sufficiently beneficial to justify their
application, at least in amounts not to exceed 250 pounds per acre,
put the results do not seem to indicate that when applied alone they
are of enough effect to warrant their use.

That the results obtained in the above experiments are attributable
to the applications given to the soil there can be no doubt, but the
applications have been made to small samples under ideal conditions
lin regard to the manipulation of the soil and the growth of the plants.
For instance, as has been explained; the moisture content of the soil
in these experiments has been maintained at or near the optimum or
piost favorable condition at all times. Again, the' fertilizers have
»een intimately mixed with the soil — far more intimately than would
[be practicable in the field — and therefore the same degree of success
may not follow under field conditions. In the case of barnyard
; manure, green manure, and lime, however, there is undoubtedly a
physical effect in the field which does not enter into these experi-
hnents, and which, in the case of a soil like the Leonardtown loam-
poor — would very likely more than overbalance the loss which would
fcccur in field practice from the less intimate mixture of the fertilizer
and the less thorough control of the conditions. The results above
obtained are sufficiently marked to justify the suggestion that the
treatments be tried on a small scale, particularly where this type of
Boil is in a run-down condition.

The Bureau realizes the importance in this connection of a prac-
ticable field test, but this would involve much more time than has
been required in making the above experiments, and should prefera-
bly be made by the farmers themselves under the usual farm condi-
tions. Furthermore, it must be insisted that good results can be
anticipated only under the best possible conditions of tilth and
intelligent handling of the mechanical factors involved in cropping.

EXPERIMENTAL RESULTS AGREE WITH PRACTICE.

* As above stated, the results obtained with the wire-basket method
appear to be in harmony with the actual field: experience of successful
farmers in the locality. In 1900 Dr. Jay A. Bonsteel surveyed and
mapped all the soils of St. Mary County, Md., and in his report of
that year, entitled "A Soil Survey of St. Mary County, Md.," he says :

The Leonardtown loam would benefit materially from liming, except, of course,
when tobacco is to be raised. The plowing under of green crops, especially the

12

leguminous plants of the clover and cowpea varieties, furnish another method
of enrichment highly desirable on almost all the soil types of St. Mary County.
and does not present the difficulties of liming, since this kind of fertilizer is of
great benefit to the tobacco crop. These leguminous crops furnish a fair forage
for cattle during a period of. their growth, and if allowed to continue growing
they produce a mass of organic matter for incorporation with the soil : and all
the time, beneath the surface of the ground, certain minute bacteria, living on
the roots, are taking nitrogen from the air and storing it in the soil, thus helping
in the enrichment of the soil. * * *

For certain crops special fertilizers will always be necessary, and commercial
fertilizers are to be commended highly, but in St. Mary County on all soils the
use of stable manure and the plowing under of green crops are to be preferred,
while on the soils least suited to tobacco the abandonment of that crop and the
free use of lime in conjunction with organic matter have already become neces-
sary, as is shown by the forest areas given over to nature's cultivation.

During the same year Bonsteel also surveyed and mapped the
soils of Calvert County, Md., and in his report, "A Soil Survey of
Calvert County, Md.," in discussing the Leonardtown loam, he makes
the following statement :

The uniformly yellow appearance of the surface soil indicates a lack of
organic matter, which should be supplied in the form of stable manures and by
plowing under green crops, like crimson clover and cowpeas. Such a treatment
would not only increase the actual supply of plant food, but would also improve
the texture of the soil. Unless it is absolutely necessary that tobacco should
be raised upon areas of this type, the application of lime should be tried in
connection with stable manures and green fertilizers. The fact that tobacco is
not largely raised on this soil should make this line of improvement much
easier than on other types of soil to which tobacco is one of the crops best
adapted.

The following year, 1901, this same type of soil was encountered in
making a survey of Prince George Count}7, Md., and in his report
upon that area Bonsteel states:

This soil is only producing to its full capacity in the northern part of Prince
George County, where, through the use of green manures and lime, from 15 to
18 bushels of wheat per acre are frequently raised upon it. Elsewhere this
soil, type is generally lacking in organic matter. The Leonardtown loam should
furnish an excellent soil upon which to introduce stock raising and dairying at
points where market gardening can not be undertaken.

While Bonsteel has repeatedly recommended the use of green i
manure and lime, it would seem from this last statement that he had
not previously found the farmers actually putting its use into prac- !
tice. In the same report, under the heading of "Agricultural condi- ]
tions," he makes the following statement :

Upon those farms where tobacco is raised lime is little used, since its appli-
cation injures the burning quality of the leaf. Commercial fertilizers, however, j
have been used in large quantities for many years to increase the production ;
of tobacco and the grain crops. They have been considered a complete fertilizer j
in many cases, and too little attention has been paid to the restoration of j
organic matter to the soil. Recently leguminous crops in the form of cowpeus j
and crimson clover have beeji introduced and the system of agriculture improved
through this means. The production of good forage crops can only be resumed
by a more generous use of lime and the leguminous green manures. The cow-
pea seems better adapted to this end than any other leguminous crop.

In 1903 Taylor and others were sent to St. Mary County and d-c-
where to investigate the relation between the chemical constituents

13

•of the soil and its crop-producing power. Taylor, in writing from
Leonardtown, Md., under date of May 4, 1903, makes the following
statement :

There are two or three farmers in this vicinity who have gradually brought
their farms up to a very fair state of cultivation by deeper plowing, more
thorough cultivation, and by the use of cowpeas and clover as green manure.

The above statements show that a few of the more successful farm-
ers have already realized the benefits to be derived by the use of lime
land green manure, and, in fact, have begun the practice of it with
| results which are unmistakably beneficial.

FRANK D. GARDNER,
In charge of Soil Management.
Approved :

JAMES WILSON,

Secretary of Agriculture.

JUNE 2, 1905.

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