Syllabus of illustrated lecture on acid soils


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Syllabus of illustrated lecture on acid soils
Series Title:
Farmers' Institute lecture / U.S. Department of Agriculture, Office of Experiment Stations ;
Physical Description:
28 p. : ; 23 cm.
Wheeler, H. J ( Homer Jay ), b. 1861
United States -- Office of Experiment Stations
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Subjects / Keywords:
Plants -- Effect of acids on   ( lcsh )
Soil acidity   ( lcsh )
federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )


Includes bibliographical references (p. 28).
Statement of Responsibility:
by H.J. Wheeler.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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aleph - 029620653
oclc - 18118020
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A. C. TRUE, Director.







Director, Agricultural Experiment Station, Kingston, R. I.




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This syllabus of a lecture on Acid Soils, by H. J. Wheeler, Ph. D.,
Director of the Rhode Island Agricultural Experiment Station,
Kingston, R. I., is accompanied by 53 lantern slides illustrating the
topic. The syllabus and views have been prepared for the purpose of
aiding farmers' institute lecturers in their presentation of this subject
before institute audiences.
The numbers in the margins of the pages of the syllabus refer to
similar numbers on the lantern slides and to their legends as given in
the Appendix. Those in the body of the text refer to corresponding
numbers in the list of authorities and references.
In order that those using the lecture may have opportunity to fully
acquaint themselves with the subject, references to its recent litera-
ture are given in the Appendix.
Famrners Institute Specialist.
Recommended for publication.
A. C. TRUE, Director.
Publication authorized.
JAMES WILSON, Secretary of Agrielture.

WASHINGTON, D. C., November 1, 1904.


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By H. J. WHEELER, Ph. D.

The occurrence of acid soils in France, Germany, and other
portions of Europe has long been recognized. It has also long
been known that certain of the more important agricultural
plants fail to grow satisfactorily, or die outright, in soils where
, a high degree of acidity prevails. Probably no more striking
instance of injury to plants upon acid soils is on record in
Europe than that in the department of Limousin, in France.
There clover could not be grown, and the agriculture of the
country was in a miserable condition for centuries until the
S construction of a railroad made it possible to introduce lime
S with which to overcome the sourness of the soil. After liming,
clover succeeded, the cattle industry throve, and an era of agri-
cultural prosperity resulted. In parts of Massachusetts, New
S Hampshire, Rhode Island, Connecticut, New York, illinois,
Maryland, Virginia, Alabama, and other States acid soils exist,
iand hence the recognition of soil acidity is of great practical
: The most satisfactory way to have the soil tested is to send it
to the local experiment station, where the chemists intrusted
with such work are better able to judge from the tests how
much lime to use than those who are making such tests for the
first time or who have had but little experience. The best test
for revealing the need of lime which is capable of being used by
persons upon their own farms is that with blue litmus paper.
Such paper can be bought of an apothecary at trifling cost.
Strips half an inch wide and 2 inches long are convenient for
making the tests. Care should be taken not to handle the end
of the paper that is to be inserted in the soil, for if the fingers
are moist they will redden the paper so that it will appear much
as it does when reddened by acid soil. The soil to be tested


should be moistened sufficiently with water to make a thick paito
and should then be allowed to stand for half an hour or longer.
It may then be parted by the use of a knife blade or other con.
venient instrument, and after introducing one end of the litmus
paper the soil should be pressed against the sides of the paper.
After from half an hour to an hour the paper may be removed
from the soil, taking care not to tear it. After its removal'the
paper may be dipped repeatedly in water in order to wash off
the adhering soil. If a distinct red color has entirely taken the
place of the original blue color of the paper, it may be concluded
that the soil probably needs liming.
In the case of very red soils it is often better to press the blue
litmus paper against the soil than to have it surrounded by it.
If in such cases the blue color of the paper disappears and gives
place to a distinct red one, a need of lime is indicated. This
blue litmus-paper test furnishes also a good means for testing
for a lack of lime in subsoils, or soils very deficient in organic
matter, where the acid substances may be largely of mineral
origin. A good supplementary test, which is applicable only
in soils containing considerable humus, is made by means of
adding dilute ammonia water to soils. This can be bought of
any apothecary at slight expense. In making this test take
two glasses, place a level tablespoonful of soil in each, then add
water until the glasses are about two-thirds full. Now add a
tablespoonful of dilute ammonia water to one of the glasses.
Stir each with a different spoon or knife. If, after standing
some hours, the liquid in the one to which the ammonia water
was added has become dark brown or black, it may be concluded
that acid humus was probably present and hence that liming
will prove helpful.
In the case of soils which contain naturally enough lime in
suitable form the humus does not get into the acid or sour state,
but the acid substances which are formed during the decompo-
sition of plants unite with the lime, forming what is known as
"mild humus," and when such is the case ammonia water fails
to give dark or black extracts, such as are obtained with soils
containing "sour humus." If the soil is rich in lime, the inor-
ganic compounds fail to become acid even in the subsoil or :
where little humus is present and the soil will not redden blue
litmus paper.
Owing to the tendency of certain soils to acidity, it is impor-
tant that there should be at least a small amount of lime (as


! |||l' *v iew.
?' carbonate) present in the soil at all times, unless one desires -to
grow only such plants as thrive best under acid conditions.
The chemical corrective of an acid is an alkali. Caustic or
slaked lime is an alkaline substance, and its application is
i1 probably the cheapest, most effective, and most permanent
means of correcting acidity in soils. When applied to the soil
it changes under normal conditions largely to the carbonate of
lime (the form in which it is found in limestone), and it is in
this form that the larger part of the active lime of soils occurs.
As pointed out later, however, other alkaline substances, such
as wood ashes, carbonate of soda, etc., are effective means of
correcting acidity.
- Since the definite acidity or sourness of even upland, well-
drained soils has been demonstrated, and simple tests for such
soils have been pointed out, there is no reason why anybody
S .. should cultivate acid soils without being aware of it and with-
out correcting the condition by liming, if desired. 'The ten-
S dency to acidity. which exists in the case of all soils which
lack carbonate of lime is much greater when certain artificial
manures are used than where only stable manures are employed.
Bone meal, tankage, and basic-slag meal gradually correct soil
acidity, while the immediate effect of acid phosphate may be
to make it more acid. Wood ashes correct acid soils quickly,
furnishing potash to plants at the same time. The action of
carbonate of potash is similar, though the quantity that would
be used as a manure would not exert a very marked effect for
Sthe first two or three years. Kainit and muriate of potash are
R likely to increase the acidity of soils more.rapidly than sulphate
of potash. Blood, azotin," and certain other organic manures
may promote acidity to some extent, but far less rapidly than
sulphate of ammonia. Nitrate of potash is a safe source of both
nitrogen and potash for acid soils, and nitrate of soda not only
furnishes nitrogen but tends also to lessen their acidity.
With this brief review of a few of the more important facts
relating to the acidity of upland soils,, it may be of interest to
follow some of the details of the investigations in this line which
have been made at the Rhode Island Experiment Station.

Attention was drawn to soil acidity at the Rhode Island
Station in 1890 by the poisonous action of sulphate of ammonia,
which materially reduced the yield of Indian corn, even when
aAzotin is a nitrogenous fertilizer prepared from meat refuse.



it was used in connection with potasic and phospbatic nmainp .
The injurious action of sulphate of ammonia, when used toge ixr
with muriate of potash, has been claimed by Brooks'o to lbevpliO. .
to an interchange of bases and acids, by which ammonaiqam i
chlorid (which he says is a plant poison) is formed, bat it as i
been shown by Wheeler and Hartwell' that ammonium chlord :i
is itself a valuable manure if the soil is not acid; hence, if iaie
is taken to correct undue soil acidity, there need be no fear of
using sulphate of ammonia and muriate of potash in the wm
mixture; nor even of applying ammonium chlorid directly A a
In the initial experiments at the Rhode Island Station sulp0 i4 |
of ammonia was used on unlimed soil at rates of 120, 40, and i
360 pounds per acre, in addition to potassic and phosphatlo
manures. With each additional application of this snbtansc. ji
the yield fell decidedly.
1 In the view now upon the screen, showing the crop of 118,
the three rows of Indian corn in the center were grown where
but 240 pounds per acre of sulphate of ammonia were applied.
Lime was applied to the soil at the farther end of the rowa,
where the Indian corn is seen to be taller.
2 A nearer view of the corn where the lime had been employed
shows that the growth was excellent.
3 It will be observed that it was not, however, so good as upon
the limed section, where 360 pounds of sulphate of ammonia had
been employed. It was particularly striking that upon the :
unlimed soil each increase in the application of sulphate of am-
monia reduced the yield, while where the lime was applied the
yield rose decidedly with each application of the ammonium sat.
It was not alone at Kingston, R. I., that sulphate of ammonia
acted injuriously, for similar results appeared the second and
third years of its use at Hope Valley.'
4 The two lots of Indian corn at the left were grown at Hope
Valley, R. I., by the aid of nitrate of soda, used as a supple-
ment to potassic and phosphatic manures. The left-hand lot -;
grew upon the limed area and the right-hand lot where lipe
was omitted. It will be seen that there was little difference ia
the results. This was due to the fact that nitrate of soda is .
good and immediately efficient source of nitrogen for acid soil,,
and the soda present tends also to gradually lessen their acidity.
The two lots of corn at the right represent the yield pr :I
duced where sulphate of ammonia was used under exactly lt .i'
same condition as the nitrate of soda. It will be seen that the ..i
a Numbers refer to list of references on p. 28.


Slot at the left, from the limed area, gives evidence of excellent
growth. The poisonous effect of the sulphate of ammonia
-where lime was omitted is plainly shown by the corn at the

S In order to determine whether acidity or a lack of lime as 5
Food was probably the fault of the Rhode Island soil, tests
were made with Kingston soil upon four lots of lettuce," all
of which were manured alike, with a mixture constituting a
"complete" manure. Two lots of plants, represented in the
view by stones, received no further treatment, and died while
the plants were very small. The third lot from the right was
grown where a one-half ration of sodium carbonate had been
added to the soil, and the lot at the left where a full ration of
s-odium carbonate had been employed. Sodium carbonate is
: alkaline, and, like lime, is capable of reducing or overcoming
sofi acidity.
Trials of carbonate of lime and of sulphate of lime with
SbeetS' showed the inferiority of the latter compound. This
.'. s. to be expected if the fault of the soil was acidity, for the
reason that in the sulphate of lime or land plaster the lime is
icombined already with a strong mineral acid (sulphuric acid),
Sand can not, therefore, aid in overcoming the soil acidity until
Sit has undergone a reduction and transformation into carbon-
ie, a change which takes place but slowly in ordinary soils.
A further test was made with barley,' the results of which 6
: will now be shown.
The two piles at the left represent the crop produced with
!il phosphatic and potassic manures. In the case of the lot at the
extreme left, however, 4 tons of air-slaked lime per acre had
also been applied three years before, while for the second lot
no lime had been used. The seven lots at the right all received
Spotassic and phosphatic manures like the two at the left, and,
in addition, nitrogen in sulphate of ammonia.
The poor result shown by the third lot from the left demon-
strates the poisonous action of the sulphate of ammonia
in acid soil. The fourth lot from the left differed from the
third solely in the fact that 4 tons of lime per acre had been
used three years before. In the case of the middle lot, the
same amount of lime was used three years previously as in the
good lot at its left, but the lime in this instance was combined
30818-No. 3-07--2

with sulphuric acid (oil of vitriol)as sulphate of lime or1 l i
plaster, which was incapable of quickly correcting the soil id'
ity. To the fourth lot from the right caustic magnesia, whil:::
was capable of overcoming acidity, also corrected the condi-
tion. The third lot from the right received magnesia com-
bined with sulphuric acid as sulphate of magnesia (Epitso
salts), and hence it only corrected the condition slightly, if at
all. It is possible that sulphate of lime or sulphate of magnesia
may overcome the acidity of soils slightly and by degrees, par-
ticularly if they are moist and contain considerable orqgiap
matter, which two conditions are favorable to the partial elimi-;
nation of the sulphur from the soil in a gaseous combination.
The two lots at the right had each received air-slaked Hlim
three years before, at the rate of 1 ton per acre. The first two
years the results were nearly or quite as good as where 4' tons
of lime per acre were used, but it had now lost its efficiency.
An addition of carbonate of soda, an alkaline substance, to tbhei
second lot from the right, though not made in sufficient qua-i
tity to equal the action of the large amounts of caustic magnesi
or lime, nevertheless helped matters decidedly.
7 Other results with barley' indicate that the soil under.
examination at the Rhode Island Station was helped by limpk
by virtue of its overcoming acidity. The nine lots of plant
were manured alike with potassic and phosphatic manures, ani
nitrogen in sulphate of ammonia was used in like quantity .1.
every instance.
Potassium was applied to the lot at the left, combined wi
chlorin as potassium chlorid, and hence it could not redu6i
the acidity of the soil. The second lot from the left receive
its potassium in potassium carbonate, an alkaline substanot
The quantity used was small, but it nevertheless counteract
the acidity enough to show a distinct advantage over the lot.
the extreme left. The third lot from the left received its poA
sium in wood ashes. The potassium in this case was probs
wholly, or at least chiefly, present as carbonate of potash,
this alkaline substance was still further aided in overcoming i.
soil acidity by the large amount of carbonate of lime and
small quantity of carbonate of magnesia contained in the a
The fourth, fifth, and sixth lots from the left received
medium, and large applications, respectively, of sodium
bonate, an alkaline substance, which was beneficial, as will..
seen, nearly in proportion to the quantity employed.
The three lots at the extreme right had received inc
amounts of magnesium carbonate in the same order. This I

I View.
,stance also overcomes acidity, though in this instance the
ainLest amount was nearly sufficient for the purpose.
Still another experiment with barley' verifies those already 8
mentioned. The six lots of barley were manured alike with
Spotassic and phosphatic manures and with nitrogen in sulphate
of ammonia. To the lot at their left no further addition had
ien made. The plat represented by the second lot from the
ilt had received one ton of air-slaked lime per acre several
I!yers before, but it had now lost the power, which it retained
:,or the first few years, of correcting the acidity. The third
~t had received several years previously four times as much
air.-slaked lime as the second lot. The fourth lot from the
ft had received caustic magnesia, which was highly effective
:correcting the poor conditions. In the instance of the lot
nit to the right, where sulphate of magnesia had been em-
I 'ioyed, doubtless some of this substance had changed into car-
lnate of magnesia by reduction and elimination of sulphur
ma gaseous combination; nevertheless, the result was poor as
Shpmpared with that obtained with caustic magnesia, which
Sitter compound was far better able to reduce the acidity of
I' soil.
i The lot at the extreme right was grown under the same con-
Si editions as the second one from the left, with the exception that
| it had received a generous application of carbonate of soda.
I I t will have been observed throughout that marked and last-
i~i~ g improvement of the soil conditions resulted only in cases in
Which such materials as were capable of reducing or overcom-
Sing soil acidity were employed. While there can be no ques-
tion but that these substances improved the physical properties
of the soil in certain cases, and in some instances doubtless
proved of some value as direct plant foods, the evidence that
their beneficial action was chiefly by virtue of neutralizing
acidity appears to be indisputable. It seems to be established
] by these experiments that certain upland and well-drained soils
are sufficiently acid to seriously injure certain plants, and that
the condition of the soil in this respect is capable of being
-greatly injured or being much benefited, dependent upon the
manures employed.
The influence of soil acidity upon the assimilability of nitro-
gen,"' as determined at the Rhode Island Station, is exhibited
by the two views which follow. In both instances nitrogen,
when used, was applied at the same rate per acre. The lots of


plants shown in both views had at their disposal like am M:iiob
of potassic and phosphatic manures in every case.
9 The view now upon the screen shows the relative efficieney: o
various nitrogenous manures upon acid unlimed soil.i
The plants at the left illustrate the result without nitrog :l
The second lot from the left shows that nitrogen in sutphateb sF
ammonia proved positively poisonous, the result being po er
than that at the extreme left, where nitrogen was omitted.
The third lot from the right received nitrogen in roasted iand
finely ground leather, the second lot from the right had nitrogenm:
in dried'blood, and the one at the extreme right was manured
with nitrogen in nitrate of soda.
Upon the same soil the efficiency becomes vastly different after:
liming, when all of the manurial and other conditions are iden-:
10 tical with those in the previous instance. All of these lots
excepting the one at the extreme left, were grown upon limed
soil. Hence a comparison of the lot upon the extreme left with':
that at its immediate right shows the direct benefit to the barley
due to overcoming or reducing the soil acidity, and the benefit
produced by increasing the assimilability of the soil nitrogen.
The lime doubtless also helped to some extent to improve the '
physical condition of the soil.
The four remaining lots show the results with nitrogen ls.k
nitrate of soda, dried blood, leather, and sulphate of ammounia
in regular order from right to left. Upon the limed soil thel:
efficiency of the nitrogen of sulphate of ammonia rose to 992.
as compared with nitrogen in nitrate of soda at 100. Thus S it
became a valuable food instead of continuing to be a polisfoil:
The efficiency of the nitrogen of dried blood rose upon the samiuiM
basis, as a result of liming, from 45.5 to 90.3, and of leather
from 0.9 to 13.8.

At the Rhode Island Station it appears to have been demnmo.
strated positively, for the first time, that soil acidity is ant.
nistic to the disease known as potato scab, and that the irea
why wood ashes, lime, stable manure, and other alkaline ai
stances promote the.disease is that they tend to overcome ;M
lessen the soil acidity." Where all the potatoes in a giTvt I
experiment were manured in an identical manner with oai|:EN
mercial manures, sulphate of lime (ordinarily known as 1w:.


*plaster), and calcium chlorid, which were incapable of over-
coming the acidity, did not tend to promote scab, though the
reverse was strikingly true of air-slaked lime, carbonate of
*: limex and wood ashes. A like result was also obtained with
e&Ioium oxalate and calcium acetate, two substances which
; change readily in the soil into carbonate of lime.
in :'It the first view of the potatoes grown under the conditions 11
ji, ]st mentioned the scabbed product resulting from the em-
Siiployment of air-slaked lime is seen at the left. The lot at the
right grown with the regular manure was absolutely free from

: The lot at the left in this view received lime which was 12
already combined with sulphuric acid and which was not
Likely to noticeably lessen the soil acidity. The lot at the right
Iil reived calcium chlorid, which would be even less likely than
'ive sulphate of lime to reduce acidity. In the former case only
AS per cent of the tubers had any scab spots (none being badly
a. scabbed) and in the latter case no scab resulted.
This -view 'presents on the left the result with carbonate of 13
lime and on the right with oxalate of lime (calcium oxalate).
In the former case 97.5 of the tubers were badly scabbed and in
the latter all were badly scabbed.
The last view in this connection shows upon the left the result 14
m with acetate of lime (calcium acetate) and on the right with
inleached wood ashes. Where the acetate of lime was used
every tuber was scabbed so as to be unfit for market, and where
the ashes were used all were scabbed and 93.3 per cent of them
:: were rendered thereby unmarketable.
i Halsted has demonstrated recently the truth of the Eng-
i litsh statements to the effect that liming counteracts, to some
'ib extent, the tendency to "finger-and-toe" disease or "clubfoot"
i in the turnip, cabbage, and related plants. Possibly this is due
| to its producing soil alkalinity, a condition which might, per-
haps, be unfavorable to that particular disease, even though the
reverse is unquestionably true of the potato scab.
This view, taken from J. A. Voelcker's English experiments, 15
shows the relative results of the use of lime, gas lime, and of
no treatment for the "finger-and-toe" disease of turnips. At
the top the sound turnips are at the right and in the other two
cases at the left. Gas lime was used below and slaked lime
aLove. The middle lots received no treatment.'"



1~ ;IPYli

In order to determine the relative effectiveness of lime inO i
recting soil acidity, when it was introduced into the soila
when used as a top-dressing, the Rhode Island Experaii1.
Station performed an experiment with timothy upon l!r,
plats of land." The manuring was the same in every isr-b 'l
Upon one plat no lime was employed, upon another it awas hp-
rowed into the soil very thoroughly in the early autumn bef ori
the seed was sown, and upon the third it was weighed, 4lft
16 until the following spring, and then sown broadcast. Wh re
the lime was worked into the soil, a good stand of timothy ~si
secured, as seen at the right. Only a very small stand was
obtained where the top-dressing of lime was used, and where it
was omitted altogether timothy was entirely absent. In all:
except the first instance the product of the plats was chiedy
weeds and grasses other than timothy. The lot of material in
the middle was from the top-dressed area, and that at the leJt
was from that which was unlimed. i...;...

The occurrence of acid soils has been reported recently by
the experiment stations of Alabama,1' New Hampshira"
Oregon," Alaska," and Illinois.1' Maryland, Pennsylvani
and other States report benefit from liming under condition
which lead to the belief that the soils experimented upon wen.
acid. The earlier experiment of Wagner and Dorsch,. a
the more recent experiments at the Rhode Island Agricultua
Experiment Station, noted above, have demonstrated the greater
effectiveness of sulphate of ammonia after liming and show
that the beneficial effect of the lime in connection with
substance was due to its action in correcting soil acidity.
In this connection it is of interest to note that J. A. Voel
chemist to the Royal Agricultural Society of England, c
attention in 1897 to the greater falling off of the yield of
than of wheat in the Woburn experiments, where ammn
salts were used without mineral manures." This he atti
at first to ability on the part of wheat to send its roots
than barley and thus get sufficient lime to serve as plant
and he speaks of "sour" spots not furnishing an exp
of the failure of the barley, because it was a fault of the
In 1901, however, he" found, on testing the soil, that it
a distinctly acid reaction to litmus paper.
In discussing later results in 1902, he" says: "It


appear that the acidity of the soil of plat 2a had acted inju-
riously upon the barley plants and stopped root development."
A year later Voelcker adds:" "That the acidity of the soil,
brought about by the continual use of ammonium salts, or else
ite condition of the soil consequent on its formation, is the
Sause of the failure of the land to produce barley and wheat."
Voelcker found finally, in full agreement with the Rhode
Island Station, that oats could thrive upon quite acid soil and
that wheat could succeed better than barley.
Upon leaching the acid soil with water, and also upon very
complete exposure of it to the air upon a stone floor for five
Months, with frequent turning, it was rendered capable of again
supporting plants. The water used in leaching the soil was
found after a time to have nearly lost its acidity. Upon soil
where the conditions-were probably nearly, if not quite, normal
thie addition of fresh leachings from the acid soil caused plants
to tdrn yellow, and visibly affected not only barley but also oat
': plants.
SThe fact that the soil could support good growth after leach-
1ig with water effectually disposed of the original view held by
iooelcker that the trouble was due to a lack of lime as plant
food, for leaching would lessen rather than increase the lime.
I A few illustrations taken from Voelcker's experiments are of
This view shows the two plats which had been manured for 17
Sa series of years with sulphate of ammonia and chloride of ammo-
ma nia. The right-hand plat, where few, if any, barley plants are
Sto be seen, had not been limed. The plat at the left had
Received a dressing of lime at the rate of 2 tons per acre about
three years before. Liming completely overcame the ill effect
of the ammonium salts.
S Where barley was grown with mineral manures and ammo- 18
nium salts, injury to the crop was delayed somewhat, and
though it was severe by 1898 it was less serious than where the
ammonium salts were used alone. In the foreground it will be
I seen that much more barley is present than in the former view.
Here the addition of lime to the soil the year before, at the rate
of 2 tons per acre, entirely corrected the condition, as seen in
the rear.
A. D. Hall, director of the Rothamsted Station, England, in
discussing the permanent grass experiments at that station,'"
says that-
The long-continued use of manures like the ammonium salts, which are
effectively acida, must have altered the reaction of the soil and made it sour

'i: ..


on some of the plate. This is very palpable oa a plat which baus. .epn
very heavy dressing of ammonium salts alone, and on which *
is now a large amount of sorrel, except upon a small portion where chalk I
been applied.
He further adds:
A dressing of lime is, without doubt, necessary on grade land on moiet a...E
in order to neutralize the acidity produced by decaying vegetation am a9
enable the manures to exert their full effect. j.i
Hall" apparently fails to recognize that acid conditions ar:i
by no means confined to soils that are exceptionally moist, b '
are also likely to occur in light uplands. In fact, some of the 'i
acid soils experimented upon in Rhode Island were sandy ant::
gravelly hillsides, where water could not stand, and whear s
nevertheless, a considerable amount of the humus was acid.

After it had been demonstrated at the Rhode Island Statio :i
that the soil of the station farm was acid, the next step taken
was to ascertain if the condition was quite general in the Stat e
For this purpose plats of land were laid out in pairs in each
county, the soil was tested for acidity, and experiments with
barley, beets, clover, grass, and other crops were begun. In
most of the cases the acidity of the soil, as shown by blue lit.
mus paper and ammonia water, was quite marked. The plaM
were all manured alike with a complete artificial manure, lime
being carefully worked into the soil of one of each pair of plat, .
There will now be shown a succession of views illustrating ;
the benefit from liming which was observed.
19 In the experiment at Foster Center" in 1896, with table
beets, upon a soil which quickly and decidedly reddened blue .
litmus paper, the yields of beets upon the limed and unlimed
plats were 143.4 and 36.6 pounds, respectively. The crop from
the limed plat is shown at the right.
20 In a test with the same kind of beets at Slocum's the
unlimed plat yielded but 1 pound and the limed one 101.0 !9"
pounds. The barley crop (cut in the "milk") in this latter
case was increased from 3.7 to 39.1 pounds by liming. :.
21 The experiment at Foster Center" was continued in 1897Sy
with clover. The first crop upon the unlimed plat amounted'
to 140.2 pounds and upon the limed one to 195.6 pounds.
22 Upon acid soil at Hamilton, R. I., the first crop upon thq |
grass section of the limed plat amounted to 205.1 pounds and
consisted chiefly of timothy, mixed with a little redtop. Upon,. I

F 15

the grass section of the unlimed plat, represented at the right,
the total weight of grass was but 151.6 pounds. The grass was
a mixture of about equal parts of timothy and redtop.
m The clover section of the limed plat at Hamilton yielded 23
0 04.6 pounds, consisting of about equal parts of clover and
/ tedtop, mixed with a few other grasses. The corresponding
nlimed section, represented at the right, yielded but 66.9
pounds, only 3.8 pounds of which was clover, the balance being
h .aiefly redtop. The clover is the little lot, at the extreme right,
Beside the redtop, from which it was separated.
SThe second crop from the clover section of the limed plat 24
,. Hamilton' weighed 74.4 pounds, and consisted of about
equal parts of clover and grass. In striking contrast to this
yied, but 0.1 pound of clover was obtained upon the unlimed
: It, It was necessary to cut this with a pocketknife and place
|.i iz the straw hat, at the right, in order to render it visible in
S6*e photograph.
In a corresponding experiment upon the hill land at Kings- 25
te't"the crops from the clover section of the two plats were
harvested, and the clover and weeds were separated carefully.
The two lots, at the left, represent the clover and weeds upon
the limed section. The clover is at the extreme left, with the
small lot of weeds at its right. The two piles at the right show
the clover and weeds upon the unlimed section, the one at the
Extreme right being the weeds. It will be seen that where lime
Swas used weeds were nearly lacking, but upon the unlimed sec-
Stion the weeds weighed nearly as much as the clover.
In an experiment at Moosup Valley, Rhode Island,"' with 26
Smang~el-wurzels (fodder beets), the unlimed area yielded at the
7 rate of only a little over 3 tons per acre; but upon the limed
Area the yield was at the rate of over 201 tons per acre. The
view shows the exact relation of the crops, that from the un-
limed area being represented at the right.
If time and space permitted, many more striking illus-
trations of a similar nature could be furnished, but it is suffi-
cient to say that the many experiments demonstrated most
completely that acid soils were quite general in Rhode Island,
even on gravelly and sandy hillsides, and that great benefit
from liming could be expected.

Other experiments at the Rhode Island Station have given
indications that quantities of phosphorus, double the amount
said to be sufficient in certain soils for the support of crops for

. i ;?
.:' iUE.

a series of years, may be present in an acid soil, and yetit
appear to be deficient in that element, as shown by
plant test." Liming has been shown to apparently om i
considerable amount of this phosphorus into such combinati
that plants can utilize it, which is a distinct advantage~ e oo lj
ically considered. Experiments at the same station, cover
a period of ten years, have also shown that ignited iron .aii
aluminum phosphate, or roasted redondite, one of the p~;l ~-
phatic constituents of certain commercial fertilizers, is of fWI I
or no value upon acid soil, but that its manurial elfficieas y hii
greatly increased by liming."'

The lime experiments of the most popular interest in conned .
tion- with acid soil are probably those to ascertain the ee i t
soil acidity upon the growth of various plants. This line of:
work was begun at the Rhode Island Station in 1893, and about
two hundred different kinds of plants have already been tensed.
The trials were made upon four plats of land which were
manured alike as concerns potassium, phosphorus, and ma
nesium. Each of the four plats received the same amount of
nitrogen. Upon two of them it was applied in nitrate of soda,
and upon the other two in sulphate of ammonia. One of mobe::
of these pairs of plats was limed at an equal rate, so as to redn ee:
or overcome the acidity of the soil. The lines of plants wer
then run across each of the four plats. Before proceeding to..
show some of the results secured in this experiment, attentioniI
should be called to the fact that the plant assimilates the ntrio :
acid of the nitrate of soda, and there is a tendency for soda to
accumulate in the soil. On the other hand, where sulphiti,
ammonia is applied, the ammonia is changed to nitric acid within
the soil and is taken up by the plants or leaches away in comW,.
nation with bases, such as potash, lime, magnesia, or soda, thu
leaving sulphuric acid behind, which in turn removes still monr
bases. Thus the tendency in using nitrate of soda is to redui ,
the soil acidity; and the tendency in using sulphate of amm-oml
on the contrary, is to produce or increase acidity. For
reasons the chemical reaction of the plates, so far as oBODSW|
acidity and alkalinity, even if not limed, becomes quite a i
with the lapse of time. Even upon limed plats there is a oiti
dency to acidity in the case of the plat receiving suaphit
ammonia, and to alkalinity in the one which receives nitrxf,:4.
soda. For this reason, those plants which thrive much b e ie

-^H """" 2*


upon the unlimed plat which receives nitrate of soda than upon
the corresponding one manured with sulphate of ammonia are
the ones which, as a rule, are the most sensitive to soil acidity
Land consequently most helped by liming upon acid soils.
A general view of the plats will aid in making the subsequent 27
views better understood. The path shown in the center passes
S.between the two plats which receive sulphate of ammonia. The
limed plat is on the left. It will be seen in the background that
some kinds of plants were making a good growth, even upon
the unlimed plat. The other two plats in the experiment,
Which are at the immediate left of these, are only partially seen.
These receive nitrogen in nitrate of soda, the limed plat being
at the left, as in this instance.
The view now upon the screen shows that amber cane 28
(sorghum) and Kafir corn refused to grow upon the unlimed
plat, where sulphate of ammonia had been used, even though
Sthe seed of each germinated satisfactorily.
This view shows the result with the same manures, but with 29
the addition of lime. These plants evidently can not endure
great acidity.
I The two lots of tobacco at the left were from the plats manured 30
with nitrate of soda, the two at the right from the plats which
received sulphate of ammonia. The larger lot at the left in
each pair was from the limed plat.
The results with rye, oats, wheat, barley, and sorghum are 31
' now shown. The products of the plats which received nitrate
of soda are in each case on the left, and the left hand lot in each
pair was from the limed plat. It will be recollected that lime
was decidedly helpful in all of the cases where sulphate of
Ammonia was used. The result is, however, less marked with
nitrate of soda. It will be observed that rye is least injured by
acidity. This, in turn, is followed by oats, wheat, and barley,
in regular order. The sorghum (early amber cane) was entirely
killed upon the unlimed plat, which received sulphate of
Ammonia, which explains the presence of but three lots. It will
be recollected that this is the same order in which Voelcker, of
S England, afterwards noted injury to oats, wheat, and barley
Supon the soil at Woburn, England, where ammonium salts had
been used with ill effect.
I In this view of German millet the crops produced by the aid 32
of nitrate of soda are at the left. The crop at the extreme left,
which was from the limed plat, was not as good as from the un-
Slimed one. In the case where sulphate of ammonia was used


liming proved helpful. It appears, therefore, that mAi6: .
unable to endure great acidity, though slight or moderate ad
ity seems more favorable to its growth than alkalinity.
33 The cantaloupe fails to thrive upon acid soil. In ie
instance the larger pile is from the limed plat. The orep
from sulphate of ammonia is in each case poorer than Itret
nitrate of soda. "
34 The watermelon is the opposite of the cantaloupe, ad it.
natural home seems to be upon acid soil. The small lots ar, %
in both instances, from the limed plates.
The products with nitrate of soda, at the left, were in no
case equal to that upon the very acid, unlimed plat widch
received sulphate of ammonia. It is of interest to see that the
watermelon thrives best under soil conditions where Kar :
corn, sorghum, barley, and the cantaloupe fail.
35 The cabbage is injured by soil acidity, for in both instances .
the limed lots are the better. Nitrate of soda, represented at
the left, was superior to sulphate of ammonia. ,
36 Alfalfa is not suited by an acid soil, for on the unlimed plat j
manured with sulphate of ammonia every plant died. And
even when nitrate of soda was used wonderful improvement,
was wrought by liming. The crop from the limed plat whihe
received sulphate of ammonia is shown at the extreme left
The crop from the limed plat which received nitrate of soda i
at the extreme right.
37 The relative amount of timothy and redtop in grass mir.
tures is materially influenced by the chemical reaction of the
soil. Redtop can thrive upon very acid soil, but timothy caS, .
not; hence "the survival of the fittest" results under the con-
ditions which happen to exist. Here is seen at the right the
larger proportion of redtop upon the acid, unlimed plat whii e
receives sulphate of ammonia.
38 It will be observed that upon the limed plat which receives
sulphate of ammonia the major portion of the grass is timothy, t i
the redtop being shown, as before, at the right. These Rhoi de i
Island experiments have shown why that State is famous for" |;|
its Rhode Island bent. It is because the bent, like redtop,:
thrives upon acid soil. Kentucky bluegrass, timothy, and oesr '
tain other grasses are likely to wholly disappear if the eil MR
acidity becomes great. ,
39 Crimson clover can thrive upon soil that is slightly acid, bnt: '
it is helped decidedly by liming on very acid soil. The tw'"

i ,


large piles are from the limed plats. Upon the unlimed plat
manured with sulphate of ammonia it practically failed.
.In this view the plants from the two plats which received 40
sulphate of ammonia are at the left and those manured with
nitrate of soda are at the right.. The plants in the second lot
From the left and those at the extreme right are in this case
.from the limed plats. The carnation pink can exist upon very
acid soil, but it is, nevertheless, greatly helped by liming.
The broom corn from the plats receiving sulphate of ammo- 41
nia is at the left and from those receiving nitrate of soda at the
right. The second lot from the left and the one at the extreme
right were from the two limed plats.
S The chicory roots are arranged in the same order as the 42
broom corn and carnation pink. In this instance little or no
* difference in the yields resulted, and it is evident that chicory
can be grown successfully even upon quite acid soil.
The order of arrangement of the flax shows the results with 43
sulphate of ammonia at the left and with nitrate of soda at the
right. The products in the second bundle from the left and at
the extreme right show little, if any, benefit from liming.
Flax, therefore, like chicory, is well adapted to acid soil.
The onion which is now shown stands in striking contrast to 44
chicory and flax, for only one or two very small onions were
obtained from the unlimed plat, manured with sulphate of
In the case of the two lots at the right, which were grown
With the aid of nitrate of soda, liming raised the yield from 24
pounds to 44.3 pounds.
SThese results appear to give the first satisfactory explana-
tion why farmers in certain sections of the country have been
; unable to grow onions successfully with commercial fertilizers.
In certain instances the recent use of lime has overcome the
-For the same reason the poppy, which thrives upon an alka-
line soil, has never been able to gain a foothold as a weed in
regions where acid soils abound, a fact which the Rhode Island
experiments have demonstrated and which may be useful to
the United States Department of Agriculture in its attempts
to grow the poppy for the production of opium. This should
be a useful hint to those who grow the poppy either for the
flowers or seed.
The serradella, unlike sainfoin, the clovers, the lentil, vetch, 45
peas, and certain other legumes, thrives readily upon soil that

onions, lettuce, spinach, beets, cantaloupes, aspjRFug '.
many other plants. In fact, the two lots at the left,.
with the aid of sulphate of ammonia, were apparently as
as those at the right, which were manured with nitrate o f
It has been found that liming heavily immediately
growing the crop, though very helpful to red clover,: uurbi
injuriously to the serradella.
The soy or soja bean and the southern cowpe are two other
legumes which are little in need of liming just before they arp
to be grown even upon quite acid soil, though in sbseq et
years the liming may show beneficial effects upon their gnr wd.
This benefit from liming in subsequent years is possibly tre
of the soy bean to a greater extent than of the cowpea.
46 Every lover of pumpkin pies will be glad to know that the
liming of acid soil promotes the growth of the pumpkin. The :
marked advantage of nitrate of soda over sulphate of ammonis
is shown by the better pumpkins in the two piles at the right, '
as compared with the two corresponding lots at the left, grows
with the aid of sulphate of ammonia. The second pile from
the left and the one at the extreme right illustrate, when -com n-
pared with those at their immediate left, the advantage from
liming the soil.
47 But three lots of asparagus plants are shown, for the rea m
that all of the plants upon the unlimed plat, which received'
sulphate of ammonia, died during the first and second y'er!iap
after they were set. The greater size of the tops shown at the j
right, as compared with the lot in the middle, illustrates the
advantage from liming, even when nitrate of soda was employSed
The results upon the limed plat which received nitrate of o0!i:
were decidedly better than upon the limed plat where ulphami
of ammonia was used. The yields of marketable asparagsii
stood in the relation of 9.62 to 5.87 pounds upon the repeaeti
48 The cranberry plants grew best of all upon the unlimed
where sulphate of ammonia had been applied. This isre
sented by the lot at the extreme left. The lot at the immed
right of it shows the great injury which may result from
Again, where nitrate of soda was employed the vines from
limed plat, which are shown at the extreme right, are
inferior to those at the immediate left, where lime was o .
49 These marked differences in the relation of plants to,
conditions are not confined to herbaceous plants, for even

Squince, as seen, is much helped by liming. The two results
S with sulphate of ammonia are at the left and with nitrate of
soda at the right. The second bush from the left and the
-one on the extreme right are the ones grown upon tde limed
S The Norway spruce, unlike the quince, is injured by liming. 50
SThe right-hand tree of the left pair, manured with sulphate of
ammonia, is inferior to the one on the extreme left, where no
lime was used. Again, looking at the right-hand pair, which
Grew upon the plates where nitrate of soda was used, the right-
hand or limed one is inferior to the other.
The pair of apple trees at the left grew upon the plats which 51
Received sulphate of ammonia and the pair at the right where
Nitrate of soda was used. The better growth of the tree at the
right of each pair shows that lime was advantageous. Never-
theless, apple trees can grow fairly well upon soil which is quite
I acid. What the effect of liming would be upon the yield of
fruit and the qualtiy of the product could not be ascertained,
owing to the necessary removal of the trees after a few years'
S The influence of liming acid soil upon the quantity of hay
produced is well illustrated in a series of experiments with
.different phosphates at the Rhode Island Station. There are
ten plats upon unlimed land, one of which receives no phos-
phatic manure, nine different kinds of phosphates being em-
* played upon the remainder of the plats.
The ten piles of hay show the crop from these ten unlimed 52
plates. The treatment of the plats with phosphatic manures,
Beginning at the left, is as follows: First, dissolved bone-black,
dissolved bone, acid phosphate, finely ground bone, basic slag
meal, floats, raw iron and aluminum phosphate, ignited iron
and aluminum phosphate, no phosphate, and double super-
The crops upon the ten limed plats are, as will be seen, much 53
greater than upon the acid soil, where lime was omitted. The
ame order of phosphatic manuring, from left to right, was
followed as in the preceding instance. A most interesting
feature of this experiment is the fact which has been men-
tioned already, viz, that ignited iron and aluminum phosphate,
also known as roasted redondite, which contains about 35 per
cent of reverted or available phosphoric acid, is of very inferior
value, even immediately, when used upon acid unlimed soil,
and so far as its after effect is concerned it amounts to practi-

- r _______I


cally nothing upon most agricultural plants. When t
limed, however, both the immediate and after effects aee
increased. These facts emphasize the necessity of teslt'l
and of liming, if necessary, if it is hoped to secure good-"
from such ready-mixed commercial fertilizers as contain ti
ignited iron and aluminum phosphate. Nevertheless, good l.p-
of such plants as are not greatly injured by acidity can still :i
produced for a series of years under the same conditions w ith
out liming, provided the phosphorus is supplied in basic gairlK
meal, bone (either steamed or acidulated), acid phosphate, die-
solved bone-black, or double superphosphate.
From what has been shown in this lecture it seems probable .
that there is a certain chemical reaction of the soil that roep
sents the best condition for each kind of plant. Many of those
best suited by a certain degree of acidity seem nevertheless to::!
thrive where a considerable degree of alkalinity exists. On he
other hand, certain plants that appear to thrive best on an *k-
line soil are able to endure considerable acidity. There l s
also groups of plants which are very sensitive to any wide
departure in either direction from the optimum. The Rhode
Island experiments with plants are being conducted upon plat
representing four different degrees of acidity or alkalinity, sad
hence throw considerable light upon the range of various pla~h ,
at least so far as concerns their limits, for acidity.
It is not expected that every person who has an acid soHil wl
derive the same benefit from liming that has been observed a
Rhode Island, unless the soil is equally acid and the phyrdica
and other conditions are similar, yet the Rhode Island expeNl-
ments ought to serve a very useful purpose as a guide to the
manurial treatment of acid soil in adapting it to the particl.t
crops to be grown.
The facts which have been presented teach that there is atR
much to learn concerning the individual requirements of i
crops which has heretofore been neglected, and which must
taken into account in a rational system of agriculture. '
For the benefit of those who may y desire to employ IImeI, i
practical suggestions about liming may not be out of pl.aew .
this point. ,
First. Sandy soils should not be limed heavily. For
soils carbonate of lime and wood ashes are to be preferred& N
slaked lime is to be used upon such soils, that which has be::en:


. joug exposed to the air is best. Half a ton to a ton of slaked
g. "me per acre or twice that quantity of either ground limestone
or wood ashes may be used in a single application.
'i: Second. For very heavy clay soils, or such as are rich in sour
SIAmmus, twice as large amounts of lime may be used as for
Im ndy soils. For use upon such soils pulverized burned lime
I or water-slaked lime may sometimes be preferable to finely
ground limestone or wood ashes.
SThird. To make liming immediately effective, the material
should be spread upon the furrows and be harrowed into the
I soil most thoroughly. When applied in grain drills its benefits
Share often not strikingly noticeable the first year, owing to the
fact that it does not become intimately mixed with the soil until
after the first season.
SFourth. After- being sown, the lime should not lie upon the
surface over night or during a storm, but it should be intro-
Sduced into the soil at once. If potatoes are grown in rota-
tions, the liming should follow the removal of the potato crop.
One exception to this might be made if potatoes must be grown
Sat the outset when one is taking up acid-exhausted soil. In
such a case it is often better to lime before planting the first
crop, though in later years liming should be deferred until
after the potatoes are harvested. In no case should treatment
of the "seed" tubers with corrosive sublimate solution (1 to
1,000) or formalin be omitted, or serious injury from potato
I scab will be likely to result.
Fifth. In liming in the course of a rotation, applications at
intervals of from five to six years are usually sufficient. The
Slime should, if possible, be applied just before a crop which is
especially likely to be helped by it, and the more indifferent
crops may be introduced later.
Sixth. The lime may be slaked in small piles in the field or in
larger piles at one side, or it may be air-slaked in a water-tight
building, so that there may be no danger of fire. In the case of
small piles, some moist soil thrown over the lime facilitates
I .slaking. Sprinkling the burned lime with the proper amount
i of water will make it slake quickly to a powder. Full directions
for slaking and using lime are to be found in Farmers' Bul-
.letin No. 77, published by the United States Department of
Seventh. Magnesian lime may sometimes be used to advan-
Stage in place of pure lime, but it should not be used repeatedly
ion the same land.
Eighth. Other substances than lime may be used to correct

liable to produce other undesired results as lime.

Ninth. It should be remembered that land plaster, alm i

Sas gypsum and sulphate of lime, is not capable of ta ti
place of wood ashes, slaked lime, ground burned lime, oi

verized limestone in neutralizing soil acidity.

'- ': i "', '.. |
.. i



.. ... .. : ;: ;;
:" l :"
:9,:4 .
... jH~l::

I lllq
U ..!!ii
j,, ii
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... Jd !
JYL! di


Soa of
1. Indian corn, Kingston, 1893.
i Shows in foreground, center three rows, effect of 240 pounds sulphate of ammonia
per acre.
S. Indian corn, Kingston, 1893.
I Effect of 240 pounds sulphate of ammonia per acre used with lime.
8. Indian corn, Kingston, 1893.
Effect of 360 pounds sulphate of ammonia per acre used with lime.
S4. Indian corn, Hope Valley.
Explanation on the photograph.
5. Lettuce. Nos. 57, 58, 59, 60. (Pot numbers used in the original station
S. publications.)
i Lots 57 and 58 without sodium carbonate. Lot 59 with a half ration. Lot 60 with a full
S ration.
6. Barley.
Showing effect of lime, caustic magnesia, magnesium sulphate, and sodium carbonate,
with sulphate of ammonia.
7. Barley.
Showing effect of caustic magnesia, sodium carbonate, wood ashes, potassium chlorid,
S and potassium carbonate, with sulphate of ammonia.
8. Barley.
Showing effect of lime, caustic magnesia, and magnesium sulphate, with sulphate of
9. Barley.
Showing effect of nitrogenous manures upon acid soils.
,10. Barley.
Showing effect of nitrogenous manures upon limed soil.
.i11. Potatoes.
W Scab experiments, air-slaked lime and unlimed.
S1. Potatoes.
i: Scab experiments, calcium suphate and calcium chloride.
18. Potatoes.
Scab experiments, calcium carbonate and calcium oxalate.
14:. 'Potatoes.
Scab experiments, calcium acetate and wood ashes.
15. Turnips.
English experiment, "finger-and-toe" disease.
1;. Timothy experiment.
Lime worked into soil and as top-dressing, left-hand lots unlimed.
1.7. Barley, Woburn, England.
Ammonium salts with and without lime.


No. of
view. .
18. Barley, Woburn, England.
Ammonium salt and minerals.
19. BeetA, Foster Center, R. I.
Unlimed. Limed.
20. Beets, Slocums, R. I.
Unlimed. Limed.
21. Clover, Foster Center, R. I.
Limed. Unlimed.
22. Grass, Hamilton, R. I.
Limed. Unlimed.
23. Clover and grass, Hamilton, R. I.
Limed. Unlimed.
24. Clover, Hamilton, R. I.
Second crop. Limed. Unlimed.
25. Clover and weeds, Kingston, R. I.
Limed: Clover, weeds. Unlimed: Clover, weeds.
26. Mangel-wurzel, Moosup Valley, R. I.
Limed. Unlimed.
27. General view.
Sulphate of ammonia" plats, Kingston, R. I.
28. Kafir corn and sorghum.
Showing failure upon very acid soil.
29. Kafir corn and sorghum.
Showing growth after liming.
30. Tobacco.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammona.
31. Oats, rye, sorghum, wheat, and barley.
Limed and unlimed.
32. Millet.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
33. Cantaloupe.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
34. Watermelon.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
35. Cabbage.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
36. Alfalfa.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
37. Timothy, redtop.
Unlimed plat, sulphate of ammonia.
38. Timothy, redtop.
Limed plat, sulphate of ammonia.
39. Crimson clover.
Limed, unlimed: Nitrate of soda. Limed, unlimed: Sulphate of ammonia.
40. Carnation pink.
Unlimed, limed. Sulphate of ammonia. Unlimed, limed: Nitrate of soda.
41. Broom corn.
Unlimed, limed: Sulphate of ammonia. Unlimed, limed: Nitrate of soda.
42. Chicory.
Unlimed, limed: Sulphate of ammonia. Unlimed, limed: Nitrate of soda.
43. Flax.
Unlimed, limed. Sulphate of ammonia. Unlimed, limed: Nitrate of soda.


F: of
14. Onions.
Unlimed, limed: Sulphate of ammonia.
14. Sqrradella.
I Unlimed, limed: Sulphate of ammonia.
46. Pumpkin.
Unlimed, limed: Sulphate of ammonia.
i47. Asparagus tops.
Unlimed, limed: Sulphate of ammonia.
. Clanberry vines.
Unlimed, limed: Sulphate of ammonia.
;A9. Quince.
Unlimed, limed: Sulphate of ammonia.
O. Norway spruce.
Unlimed, limed: Sulphate of ammonia.
|1. Apple trees.
Unlimed, limed: Sulphate of ammonia.
!9. Grass.
Unlimed phosphate plate.
8. Grass.
., Limed phosphate plate.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.

Unlimed, limed: Nitrate of soda.



^ 1. Agriculture, 2 (1901), p. 255. The Home Correspondence School,
King-Richardson Co., Springfield, Mass.
\ 2. Rhode Island Sta. Rpt. 1901-2, pp. 295-304. "
3. Rhode Island Sta. Rpt. 1890, pp. 49-56.
4. Rhode Island Sta. Rpt. 1893, p. 203. 4M
5. Rhode Island Sta. Rpt. 1895, p. 267.
6. Ibid., p. 269.
7. Ibid., p. 31.
8. Rhode Island Sta. Rpt. 1899-1900, p. 302.
9. Ibid., p. 311.
10. Rhode Island Sta. Rpt. 1897, pp. 241-249.
11. Rhode Island Sta. Bul. 40, also several previous bulletins, referred
12. New Jersey Stas. Rpts. 1894, p. 285; 1895, p. 265; 1896, p. 304.
13. Jour. Roy. Agr. Soc. England, 64 (1903), p. 347.
14. Rhode Island Sta. Rpt. 1899, pp. 171-173.
15. Alabama College Sta. Bul. 92, pp. 107-112.
16. New Hampshire Sta. Rpt. (Bul. 59), pp. 181, 182.
17. Oregon Sta. Rpt. 1898, p. 41.
18. U. S. Dept. Agr., Office of Experiment Stations Bul. 82.
19. Illinois Sta. Circ. 64.
20. Die Stickstoffdiingung. Berlin: Paul Parey, 1892, pp. 216-219.
21. Jour. Roy. Agr. Soc. England, 3. ser., 8 (1897), pp. 287, 288.
22. Jour. Roy. Agr. Soc. England, 62 (1901), p. 286.
23. Jour. Roy. Agr. Soc. England, 63 (1902), p. 314.
24. Jour. Roy. Agr. Soc. England, 64 (1903), p. 361.
25. Ibid., p. 93.
26. The Soil. New York: E. P. Dutton & Co., 1903, pp. 157, 158, 221.
27. Rhode Island Sta. Rpt. 1896, after p. 288, fig. 10.
28. Ibid., fig. 11.
29. Rhode Island Sta. Rpt. 1897, after p. 198, fig. 5.
30. Ibid., fig. 1.
31. Ibid., fig. 2.
32. Ibid., fig. 3.
33. Ibid., fig. 17.
34. Ibid., fig. 19.
35. Rhode Island Sta. Rpt. 1898, pp. 122-132.
36. Massachusetts State Bd. Agr. Rpt. 1903, p. 153.
37. Rhode Island Sta. Rpts. 1893, pp. 224-252; 1894, pp. 152-167; 1895, ppl. i
214; 1896, pp. 224-272; 1897, pp. 202-225; 1898, pp. 144-170; Buls. 69, 96.


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