New Series December, 1936 Number 3
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STATE OF LORIDA -"
Department of Agriculture
NATHAN MAYO, Commissioner
Ne Seie Deemer 136 Nube
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STATE OF FLORIDA
Department of Agriculture
NATHAN MAYO, Commissioner
General Principles ............... ........................ 5
Sources and Functions of Fertilizer Elements.................. 12
Home Mixing ................................ ...... ......... 26
Fertilizer Formulas ....................................... 27
Tilth ................................................... 45
Sulphur Fertilization ...................................... 50
Soil Analysis ............................................... 57
Purchasing Fertilizer ............................... ..... 59
Citrus Fertilizer Experiments ............................... 65
Practicability of Fertilization of Citrus Groves................. 90
Cotton Fertilizer .......................................... 97
Fertilizing Peaches ........................................ 102
More About Fertilizer ...................................... 108
Useful Tables ............................... ...... .... 105
Soil Organisms ............................................. 123
Uses of Lime ............................................. 180
Some Results of Soil Fertility and Fertilizer Experiments with
Tomatoes ............................................. 185
Revised Statistics on Consumption of Fertilizer in the United
States ........................................... ...... 141
Manganese Deficiency in Sand Cultures....................... 152
Manganese Sulphate ....................................... 155
New Laws ................................................. 160
SOILS AND FERTILIZERS
By T. J. BROOKS, Assistat Commissiner of Agricultre
PHYSICAL man is made up of some eighteen of the
eighty known elements composing the material uni-
verse. Man's existence is dependent upon his ability
to make the soil yield him a sustenance.
Soils are made up of small particles of different kinds
of minerals mixed with more or less organic matter. All
geologists tell us that these small mineral particles were
originally formed by the breaking down of rocks through
glacial erosion, weathering, and decomposition. The min-
eral kingdom is the basis of the vegetable and animal king-
doms. Plants and animals are partly mineral-man is no
So far, science has been able to isolate eighty distinct "
physical elements. At least eighteen of these are essential
to the growth of plant life-carbon, hydrogen, oxygen
magnesium, iron, sulphur, calcium, phosphorus, and potas----
sium, are the more important.
The elements taken entirely from the soil are, calcium,
iron, magnesium, phosphorus, potassium, and sulphur.
Nitrogen is taken chiefly from the soil, but a group of
plants known as legumes-such as clover, peas, beans,
vetches, cow-peas, alfalfas, etc.-gather part of their nitro-
gen from the atmosphere. They accomplish this by means
of microscopic organisms which live in small nodules or
tubercles found on the roots.
Combinations of the three elements, carbon, hydrogen,
and oxygen, constitute 95% of all plants. They form the
fats and carbohydrates, including the oils and starch.
Plants obtain their supply of these from the air and water.
The carbon is derived from the carbon dioxide gas of the
air, and the hydrogen and oxygen from water, which is
itself a combination of hydrogen and oxygen absorbed
through the roots.
6 DEPARTMENT OF AGRICULTURE
So that only about five per cent of the material of plants
actually comes from the soil. 'Only minute amounts of
magnesium, iron, and shlphur are required and they are
present in most soils in abundant quantities. The same is
usually true of calcium, although certain crops, particularly
clover, require this element in considerable amounts. So,
by process of elimination, we find that seven of the eighteen
elements essential to plant growth, need give the farmer
but little concern.
The efficiency of soil is measured by its capacity to sup-
ply plants with the several materials and conditions they
require for growth; these include physical support, water,
heat, air and food. These elements of healthy plant en-
vironment must exist in well-balanced proportion and
abundance to insure bountiful yields-even from the best
of cultivation and the absence of disease and insect or
animal enemies. The vast variety of'climates, soils, and
soil conditions determine the kind and location of the many
varieties of plants.
Generally speaking, the water, heat, and air are fur-
nshed by nature. It also furnishes the food in great
measure, but of recent years a great deal of artificial feed-
J(ng of plants has been practiced by farmers. This gives
rise to the manufacture and use of fertilizers.
Nitrogen, phosphorus, and potassium are three elements
/ which in their various combinations, constitute the vast
majority of the material obtained from the soil by plants.
These elements do not exist in the soil as single elements,
but are found combined with other elements, and plants
can only Wappropriate their foods when they exist in cer-
tain combinations, and under certain physical conditions.
The following mineral elements are also needed by plants
in different degree and proportion: Iron, manganese,
chlorine, sulphur, silica, carbon, iodine, bromine, boron and
No chemical analysis of either the soil or the plant will
show dependably and accurately just the combination of
ingredients which should be used. Soil analysis shows the
chemical content, but does not show conclusively the avail-
ability of plant foods. The mechanical condition, which
cannot be ascertained by chemistry, goes farther in de-
termining the fertilizer needed, than the actual plant food
taken up by the growing plant. It is also true that a crop
SOILS AND FERTILIZERS 7
test is the only absolutely reliable means of determining
the availability of plant food in fertilizers, as that avail-
ability is largely determined by the physical or mechanical
condition of the soil.
The Federal Bureau of Soil Surveys, of Washington, D. C.,
has found over 6,600 combinations of soils in the United
States. Florida has a hundred varieties. There is but little
information to be derived from a soil analysis that would
be of benefit to farmers. So much depends on, drainage
and various physical conditions that an analysis made under
laboratory requirements is of little value.
A chemical analysis may indicate a very fertile soil, rich
in plant food, while the facts are the soils are not produc-
tive. This is instanced by the rich muck lands and river
bottoms of the State, that are fertile chemically, but not
productive until properly drained and sweetened by the
use of lime; also, by the arid lands of the west, rich in the
elements of plant food, but not productive until irrigated.
Other soils, with less plant food, but on account of proper
physical conditions are exceedingly productive.
The discovery that the kind and amount of fertilizer
wudich should be used on a certain soil to insure the best
result from a certain crop can be ascertained only by actual
test in growing it, was a sore disappointment to agronomists
and is disconcerting to the farmer.
There are several methods used in determining the avail-
ability of plant foods in fertilizers; the neutral perman-
genate method, and the pepsin hydrochloric acid method
are used to determine the availability of plant foods, and
they differ so widely that 65% as shown by the latter is
equal to 85% as shown by the former. The Kjhldahl method
is also used to ascertain the nitrogen content of ingredi-
ents making up a compound fertilizer, but the availability
for plant food of the elements contained is not so easily
All the power of growth possessed by plant life is de-
pendent upon the presence and availability of the plant
foods with which the rootlets come in contact.
One food cannot take the place of another. No amount
of preparation, seed selection, or cultivation will produce
a crop when the proper plant foods are not in the soil. If
8 DEPARTMENT OF AGRICULTURE
two are there in superabundance, and the third totally
absent, the labor is lost. We fertilize when we apply either
ammonia, phosphoric acid, or potash in an available form.
A complete fertilizer must contain all three, but not neces-
sarily in equal parts. The food that is present in least
amounts limits the crop. Plants need a "balanced ration"
the same as animals.
Plant food is drawn in through the tiny, hair-like fibrous
rootlets. Each of these fibrous feeders is covered with a
thin skin. All the food plants get must pass through this
skin. The process is very much like that of body-building
from digested food in the stomach and alimentary canal
of animals-including human beings. The villi of the diges-
tive tract are analogous to the root fibers that take up the
soil water which holds in solution the dissolved plant food
elements. The fuzz on the roots has no perceptible open-
ings through which the finest powdered dust could get.
Plant food which will dissolve so as to go with the water
through the skin of these tiny roots is called soluble and
is therefore available for plant nourishment. The plant
food thus drawn in by the fibrous rootlets passes up through
the roots, the trunk, stalk or stem, then the branches
and out into the leaves or blades where most of the water
is evaporated, transpired, or breathed off into the air.
A process of exchange, of transpiring, and absorption takes
place in foliage-much like the process which takes place
in the lungs of animals that breathe out carbonic acid
gas and take in oxygen. The sap of plants is elaborated
in the foliage by this exchange of moisture drawn up from
the ground, and the taking in of gases from the air.
After this "elaboration," the sap flows back to build up
the plant and its fruit-just as blood flows back from the
lungs, where it is surcharged with oxygen, to the heart
and thence through the arteries to the capillaries in all
parts of the body where assimilation or body-building
Plants exposed to light develop chlorophyl, which is the
coloring matter that gives the shades to certain portions
of the protoplasm. The function of chlorophyl consists of
the absorption of carbon-dioxid gas, resulting in the trans-
formation of oxygen and the formation of new organic
A plant food is much more available when locked up in
some medium than in others. Certain sources of nitrogen
SOILS AND FERTILIZERS 9
yield it up to the action of soil moisture more readily than
others. This makes the source of nitrogen, phosphorus, or
potash of importance to the farmer, who may want either
rapid or gradual solubility to suit a quick, or slow-growing
Justice Von Liebig was the founder of Agricultural
Chemistry. It was he who discovered that plants feed on
soil chemicals, and if these are not in the soils in form
available for the growing plant to appropriate there can
be no growth and no yield of harvest. He demonstrated
how crops depleted the soil, and how worn out soils could
be restored to fertility by the application of artificial
He announced his discovery in 1840.
Next to the knowledge of plant breeding the knowledge
of plant feeding has had the most important bearing on
modern agriculture. When we think of the magnitude of
the commercial fertilizer business throughout the world it
is indeed remarkable that the knowledge of the chemistry
of the soils came to our service at so recent a date. If
the ancients had possessed this knowledge history might
have been different.
No iron-clad formula for commercial fertilizer can be
made to suit all soils. The available plant food in the soil \
and the amounts of each of the ingredients of a mixed
fertilizer that a given crop draws from the soil per acre-'/
is the basis for determining the formula for the crop.
The availability of plant food in soil, the chemists tell
us, cannot be determined in the chemical laboratory. Some
chemists tell us that it is impossible to ascertain accurately
the availability of plant foods in commercial fertilizer.
The law of Florida requires that the tag state the per cent
of total ammonia, organic ammonia and inorganic am-
monia, the available phosphoric acid, insoluble phosphoric
acid and water soluble potash, and the sources from which
these elements were obtained. Chlorine not more than....,
moisture not more than...., but it does not require that the
tag state the relative percentage derived from each source,
because of the contention of chemists that it is impossible
to ascertain with certainty the sources from which these
elements are obtained.
DEPARTMENT OF AGRICULTURE
There are three forms of nitrogen in soils, and should be
in well-balanced fertilizers-organic, ammoniacal and nitric.
The last named is soluble and immediately available for
plants. Ammoniacal nitrogen is converted into nitric form
by the action of bacteria and soil chemicals in rather a
short period. Organic nitrogen takes somewhat longer,
due to its process of being changed to the ammoniacal
form before the plants take it up. Plants get their carbon
from the air by way of its foliage and this combines with
the oxygen in the water taken up by the roots to form car-
bonic acid, which in turn, desolves compounds supplied by
the soil solution. The hydrogen in the water combines with
nitrogen to form ammonia, and this combination depends
very largely on the warmth and depth and texture of the
soil as well as on the action of favorable bacteria. The
amount of moisture in the soil goes a great way toward
determining the action of bacteria. The tilth-depth of
tillage or amount of soil available for plant roots-of soil
is as much a determining factor as the mere presence of
plant food elements. Oftentime the farmer will use barn-
yard manure in connection with commercial fertilizer, in
which case it is an indeterminate equasion as to what is the
best formula to be used. The kind, quantity and quality
of the manure would have to be known before the formula
and quantity of commercial fertilizer needed could be de-
HIGHER ANALYSIS FERTILIZERS
Generally speaking, the getting away from lower analysis
fertilizers to the higher analysis ones is quite a saving to
the farmer. Some states have enacted laws fixing a min-
imum. standard for total available plant food in mixed fer-
Stilizers. Florida's standard is fourteen per cent minimum
' for all mixed fertilizers. The value of a ton of fertilizer
lies wholly in the number of units of plant food it contains
together with the small amount of the rarer elements
which it may also carry, that are necessary to plant growth.
The higher the analysis of the fertilizer, the more eco-
nomical it is to the farmer. For instance, a fertilizer con-
taining 20 per cent total available plant food can be had,
which is made from materials equally as good as one con-
taining 14% total available plant food. There are six more
units of plant food for the same freight; a very small
amount more profit to dealer, and the same labor of han-
SOILS AND FERTILIZERS 11
dling. A twenty-eight per cent goods has an even greater
saving. However, higher analysis goods naturally contain
less of the rarer elements necessary to plant growth.
There are now appearing synthetic fertilizers, on the
market in large quantities. These will run from twenty-
five to sixty and even sixty-five per cent total available
plant food. They are concentrated chemicals and carry
nitrogen, available phosphoric acid and potash. They do not
-rry much of the other mineral elements; such as iron,
manganese, iodine, bromine, boron, lithium, copper and
magnesium; needed in sniall amounts for most plant life.
Cover crop and organic fertilizer will go far toward rectify-
ing this deficiency.
12 DEPARTMENT OF AGRICULTURE
SOURCES AND FUNCTIONS OF FERTILIZER
P URE nitrogen is a gas that has no smell, color or taste.
There is plenty of it in the air, but leguminous plants
are the only ones that can extract it from the air
and store it in the soil. Modern science enables man to take
it out of the air by power process. Ammonia is a compound
of fourteen parts of nitrogen, by weight, combined with
three parts by weight of hydrogen. The Federal Govern-
ment has a large plant for extracting nitrogen from the
air, located at Sheffield, Alabama.
It is difficult to secure an adequate supply of nitrogen.
It is found in combination with other materials but these
materials are scarce and high. Nitrogen-bearing materials
are called nitrogenous or ammoniates. It is often confus-
ing to laymen to use the words "nitrogen" and "ammonia"
as synonymous, and yet speak of them as being different
elements. This is because ammonia by weight is fourteen
parts nitrogen to three parts hydrogen.
The common sources of commercial nitrogen are:
Nitrogen. Equivalent to ammonia.
Nitrate of Soda........15 to 16 18 to 19%
Nitrate of Ammonia.... 19 to 22 23 to 26
Dried Blood ...........10 to 14 12 to 17
Tankage .............. 5 to 9 6 to 11
Fish Scrap ............ 7 to 8 8% to 9%
Cottonseed M. ......... 6/2 to 71/2 7 to 9
Castor Pomace ......... 5 to 6 6 to 7
Nitrate of Lime.
Horn and Hoof M.
Hair and Wool.
Protoplasm is the physical basis of life and nitrogen is
necessary for its production. The effect of nitrogen on
plants is to build up the body, give rich, green color to
eaf, and vigorous growth.
SOILS AND FERTILIZERS
Too little stunts growth, and too much gives rank growth
with snappy, weak, stalks, and delays ripening. Large
amounts suit plants like celery, lettuce, etc., where crisp,
tender stems and leaves are wanted. For immediate re-
sults it is best to use nitrate of soda, while for seasonal
growth other forms can be used. The activity as well as
availability of nitrogen in materials like leather scrap, hair,
or peat, is but one-fifth to one-tenth as much as that in
nitrate of soda.
No organic cell can exist without it has nitrogen in com-
bination with carbon, hydrogen, oxygen and sulphur. Plants
are nourished by the nitrogenous substances contained in
the soil and water, and animals by the nitrogenous sub-
stances in plants and other animals. However, neither
plants nor animals can utilize nitrogen unless it is fixed.
(non-volatile) in some combination.
The world's principal source of nitrogenous material in
a commercial sense has been the nitrate beds of Chile. The
United States consumed during the year 1913-taken as a
normal rate-140,000 tons of inorganic nitrogen, equiva-
lent to 658,000 tons of ammonium sulphate, of which about
two-thirds was Chilean nitrate. This material in the raw
state is blasted from the pampas of Chile. This valley was
once part of the bed of the ocean in which floated vast
meadows of sea-grass. A volcanic upheaval formed what
is now the mountain range rising sharply from the Chilean
seaboard and created a lake between that range and the
Andes, forty-five miles inland. The sea water evaporated,
the sea-grass decomposed and hardened into a mineral soil
imprisoning the nitrogen which the sea-grass had drawn
ages before from the air. The large lumps are crushed and
boiled, the first step in concentrating into exportable form
the nitrate of soda. After the caliche is removed from the
pampas it is carried in open freight cars to the crushing
house and reduced to a form which renders it the more
readily soluble in the boilers, to which the broken caliche
,is borne by an inclined conveyor belt. In the large steel
pans of the nitrate plant, exposed to the Chilean sunlight
the liquid product of the boiling vats finally yields in crys-
tals the nitrate of soda of commerce. After the mother
liquor is drawn off and relieved of iodine-one of the by-
products of the industry-and returned again to the boil-
ing vats, the nitrate of soda is left to dry and is finally
conveyed in open cars on high trestles to be dumped into
the loading platforms.
14 DEPARTMENT OF AGRICULTURE
Four-fifths of the world's nitrogen is contained in the
air. Only one-fifth is present in the soil, animal and vege-
table matter. Nitrogen in its elemental form constitutes
about four-fifths by volume or three-fourths by weight of
,the atmosphere. The atmosphere covers the earth some
fifty miles in depth, and above every square mile of the
earth's surface there is estimated to be about 21,683,200
tons of nitrogen, while the total area of the earth's surface
approximates 200,000,000 square miles.
The conversion of the nitrogen of the air into compounds
available for use may be accomplished in a number of
ways, among which are the following:
1. The direct oxidation of nitrogen and its conversion
into nitric acid.
2. The combination of nitrogen with metals to form
nitrides, which may be treated to furnish ammonia.
3. The formation of cyanides or cyanogen compounds
by the combination of nitrogen with metals and carbon.
4. The formation of a compound with carbide, produc-
5. The direct combination of nitrogen and hydrogen
nitrites and nitrates, which may be treated to furnish
In addition to being so essential to life, nitrogen is the
chief and most used element in explosives. During the
World War when the United States found itself in need of
nitrogen for the manufacture of gun powder and other ex-
plosives the cyanamid and Haber processes-the last two
mentioned above-were recommended by scientists ap-
pointed to investigate the fixation processes. As a result,
the Government built two plants, one at Muscle Shoals and
one at Sheffield, Alabama, utilizing the falls of the Ten-
nessee River to furnish the power. Plant number one was
completed, but never came into active use until the Armis-
tice. This plant was designed to produce 60,000 pounds
of anhydrous ammonia per day. Plant number two for the
production of cyanamid was completed, but operation was
suspended pending the decision as to the final disposition
of the plant. It was designed to produce 110,000 tons per
annum of ammonium nitrate.
SOILS AND FERTILIZERS 15
Under stress of war, plants were built with an annual
capacity of some 50,000 tons of fixed nitrogen. In 1917
by-product coke ovens produced 80,000 tons of nitrogen
or about 400,000 tons of ammonium sulphate.
Our grain crops, potatoes and cotton of the United
States require 6,372,000,000 pounds of nitrogen. Of this 01
amount not more than 2,000,000 tons are returned by le-
guminous crops, imported nitrates, coke ovens and farm
If water power can be harnessed to plants that will pro-
duce commercial nitrogen at a much lower cost than by the
old processes and in unlimited quantities to neglect to pro-
ceed with this work by the government or to lease it to
companies under proper contracts guarding the rights of
the public is beyond excuse. Public opinion should o
function as to impel a policy for the public welfare.
At the time of the World War the cyanamid process had
become fully developed, while the synthetic ammonia pro-
cess was still in the development stages. During the war
several large cyanamid plants were built both in America
and abroad. But none have been built since the war. On
the other hand, practically all of the enormous European
expansion of the nitrogen fertilizer industry has been
through the building of new or the enlargement of old syn-
thetic ammonia plants, until today these plants far out-
number the cyanamid plants and their output of fertilizer
is more than four times as great. The amount of nitrogen
fixed by the cyanamid process reached a peak in 1917, but
in 1918 it was passed by the synthetic ammonia process.
At the close of the war there were only two or three of
the synthetic ammonia plants in existence, but today there
are 35 or more. The world's production figures by the two
processes are significant of the tre*. in this matter.
WORLD'S FIXATION OF ATMOSPHERIC NITROGEN
By Cyanamid By Synthetic
Process Ammonia Process
Year Tons Tons
1913 ........................... 16,000 2,000
1915 ........................... 66,000 10,000
1917 ........................... 136,000 82,000
1918 ........................... 132,000 140,000
1919 .................. ........ 127,000 176,000
1921 ........................... 124,000 240,000
1923 ........................... 116,000 310,000
1925 ........................... 136,000 390,000
(Figures are nitrogen tonnage, not fertilizer tonnage).
DEPARTMENT OF AGRICULTURE
:. Phosphoric Acid "
Phosphoric acid is a compound which contains 43.7%
;phosphorus by weight. Nature does not isolate phosphorus;
it is always combined with something else-usually lime.
The principal commercial sources are phosphate rock, ecid
phosphate, bone,Land Thomas slag.
In opund p~rsphate rock, or floats, and bone black, the
-phospnoric acidis insolu&e and therefore produces effects
very slowly. These may be used-for composts where im-
mediate effect' are not needed. Raw phosphates and bone/
black are treated'with sulphuric acid, rendering them sol-/
uble,'2Wd thus producing acid phosphate. When render
available it is of equal value, no matter from what sour
obtained. Splendid results have been secured by the u e
of soft phosphate when used in sufficient quantities and
properly composed or thoroughly inoculated.
It takes 50,000 pounds of water to dissolve one pound.
of insoluble phosphoric acid. Of course, this means that
"insoluble" does not mean that which is incapable of being
-dissolved, bu4 that it is in combination of two parts of
i phosphoric acid with three parts of lime. This form is
foundd in*raw phosphate rotk and in bones. The phos-
L phorus found in bones is of greater value than that found
S? *rq&k fo the reason that bone is organic gnd decays
wh i t into the grourl m1here it rots through the work
of fk ria. Rock phosphorlt, acid is of no value until
it lhas been dissolved into soil moisture. Even grinding
itto powder won't help much, as it must be in such solu-
tion as to pass through the skin of the fibre rootlets. The
rock must be treated ith sulphuric acid, which changes
two of the three'part sJime into gypsum or land plaster
-sulphate of lime-th!Wtwo parts kill the acid and leave
the phosphoric acid combined with only one part of lime-
and the:pro4uct is acid phosphate or superphosphate.
Methods-so far used in extracting the jsphate rock from
the.soil and in preparing it for fertihzer* have been very
wasteful, as commercial acid phosphate made from 32 per
cent rock contains only 16 per cent of phosphoric acid. The
elaborate washilig and screening process now used in pre-
paring the rock for treatment with acid often results in a
loss of more than half the material. A new process recently
discovered promises to save this wtl.e. (See statement at
close of this article.)
SOILS ;AND FERTILIZERS 17
The combination of both water soluble and reverted
phosphoric acid is the form in commercial fertilizer. It is
a combination of two parts of phosphoric acid and one
part of lime. After soluble phosphoric acid has been in the
soil for a time it undergoes another clange-the lime unit-
ing wi:h the phosphorus becomes "reverted," which results
%in a combination of two parts phosphoric acid with two
,parts of lime. In this reverted form the phosphoric acid
is held in the soil, and becomes slowly available.,
In making phosphoric acid the first thing necessary is
to operate an acid plant. Sulphur ore is mostly imported
from Spain. 'his ore is burned in furnaces, the fumes
being condensed in immense lead chambers. Some nitrate
of soda is used in the process. The acid produced is trans-
ferred to an acidulating plant.
Finely ground phosphate rock-pulverized to a fineness
of about 100 per cent through a 60 mesh screen, mixed in
equal parts with sulphuric, acid at 52* (Baume)-the mix-
ing is done in flat circular pans provided with heavy stir-
rers which give a thorough mixing of the rock and acid.
From these pans the mixture, which is still liquid, is drop-
ped into closed dens and left about twelve hours, long
enough to solidify and for chemical action to render the
phosphoric acid available. It is then transferred to the
mixing plant. Acid phosphate is valuable for the percent-
age of phosphoric acid which it contains and is usimllyaJd
on a unit basis. % -
Many fertilizer manufacturers are nothing more than
mixers of the fertilizer ingredients, which they buy from:,
plants that manufacture the separate elements. They buy
the constituents at wholesale and mik according to the
various formulas and give the prod. a brand name, ad-
vertising and placing on the marlrW commercially. The
various materials for a complete fertilizer are assembled,
analyzed and run through mechanical mixers in tl-, pro-
portion that is desired. These mixtures are then laid away
to cure in large piles'-each analysis t9 itself. When the
shipping, season opens these cured piles are again run
through pulverizing and mixing machinery, put into bags
and cars and delivered to fill orders.
A double super-phosphate plant is being built on the Ala-
fia River, near Tampa. Phosphate.will be bought and then
reduced to nearly double strength to meet this demand for
18 DEPARTMENT OF AGRICULTURE
greater acid phosphate content in fertilizer. The use of
this phosphate will affect the formulas.
Materials Furnishing Phosphoric Add
Material Total Available Insaouble.
Acid Phosphate .......... 16 to 17 15 to 17 1 to 2.
Dissolved Bone Slack...... 17 to 19 15 to 18 1 to 2
Bone.Meal........:...... 20 to 25 5 to 8 15 o 17
Dissolved Bone .......... 15 to 17 13 to 15 2 to 3
Peruvian Guano ........ 12 to 15 7 to 8 5 to 8
Thdmas Slag ............. 22 to 24 22 to 24 .
Superphosphate .......... 18%
Triple Superphosphate .... 44%
In experiments Thomas slag, when finely ground, is found
to furnish a degree of food for growing plants-although
chemical tests do not indicate it. Bone meal is very similar,
but breaks down under bacterial action.
Functions of Phosphorus
Phosphorus is necessary for the development of straw,
seed, and good root systems. It gives stability and vigor
to plants, builds fiber, hardens and matures growth, and
is a ripening element. It is conducive to favorable and -
beneficial soil bacteria.
Potassium is one of the elements. The Latin name is
kalium, which is the explanation of why K stands for potas-
sium in chemistry. The oxide of potassium is a compound
of 78 parts by weight of potassium combined with six
teen jrts by weight of oxyg he chemist's symbol-
formula is su a potash KaSO0; muriate of
potash KCL; sulphate of magnesia MgSO; chloride of
magnesia MgCh; chloride of sodium NaCI; sulphate of lime
CaSos, does not contain potash.
The natural products yielding potash are:
Kainit, calculated to pure potash KO ........ 12.8
Carnallit, calculated to pure potash KO ...... 9.0
Sylvinit, calculated to pure potash K0 .......12.4
The great deposits of potash at Sassfurt, Germany,
were discovered in 1847, and the phosphate rock of South
SOILS AND FERTILIZERS 19
Carolina in 1868, and later in Florida, Tennessee, Uth,
Wynmi.n- .Mnone, KIntn"ky Arlnnna and Virgini It
as not till after the Franco-Prussian War that extensive
demonstrations of the value of phosphate and potash were
carried on. Germany had potash and no phosphate. America
had'phosphate and no potash. The Germans were exhaust-
ing the available phosphorus in the soils, and we were using
up the available potash in our soils, by an unbalanced sys-
ten of plant feeding.
The discovery of the Thomas basic slag processes of
making steels from phosphatic iron ore greatly supplemepted
the Serman fertilizer needs, but it did not help America's
need for potash. The Germans made the most of this
wonderful monopoly. The writer visited one of their largest
mines in 1913. It is a wonderful bed of crude rock salts.
The mining is easy and simple, as no extraneous matter
has to be removed. As it is tunneled there is no over-
,urden to remove and there is no seepage of water'to in-
* The "raw deals" so often handed American dealers pro-
voked extensive explorations to discover deposits, and ex-
periments to discover means of manufacturing it from
other materials containing this element. The lakes of Cali-
fornia, Utah, and Nebraska were found to contain an
abundance of potash and certain shales were found to be
workable for potash; the waste of blast furnaces, beet-
sugar mills, molasses distilleries, wool-washing plants and
cement works. The cost of manufacture thus far has been
too high to compete with the German products-about
$125.00 per ton.
During 1919 California had twelve plants and turned out
33,879 short tons; Nebraska, 10 plants, with 34,142 tons
output; Utah five plants, -nd 838866-tons. ---
Pure potassium has peculiarities that prevent its use as
a plant food. It must be combined with other elements be-
fore being ith for fertilizer) Two pa t m
with one of sulphur and four of oxygen is one combina-
tion. Sulphate of potash K2S0, potassium and chlorine,
fifty-fifty, is another which makes muriate of potash-
symbol KC1. A third combination is two combining weights
of potassium, with one of carbon and three of oxygen-
carbonate of potash K2C03. A fourth combination is one
each of potassium and nitrogen and three of oxygen. This
is nitrate of potash, symbol of KNO3.
20 DEPARTMENT OF AGRICULTURE
Potash is essential for the production of starch, fiber
and the full development of plant and seed.
Bacteria play so important a part in fertility of soil that
they hold an important place in the discussion of fertilizers.
Bacteria are microscopic organisms, microbes, fungi, or
parasites. An organism is either an animal or plant having
organs performing special functions.
By far the greater percentage of bacteria is vegetable,
both in soil and in animal organisms, but vegetable bac-
teria have no chlorophyl. The bacteria that thrives in the
human organism may be beneficial-as in the process of
digestion-or injurious-as in case of the various disease-
Bacteria live in soil. They cannot thrive where there
is no humus. There are many kinds, and each kind has
its special substances on which it thrives best. A group
known as ammonifiers, begins to grow as soon as placed
in moist soil. It lives but a short time, and the protein
which has been absorbed is changed into ammonia. When
this group dies other groups take up the ammonia, and
change it into nitrite. When it dies, another group takes
up this nitrite and changes it into nitrate. This last prod-
uct is readily soluble and is dissolved into soil moisture.
The rootlets then take it in along with the soil moisture.
Most organic and some inorganic fertilizers must be changed
by these bacteria before the plant foods become avail-
able. They need warmth, moisture, humus, and air; too
much water excludes the air and too much acid hinders
Different kinds of bacteria are needed to dissolve dif-
ferent kinds of materials in the soil. Good results have
been secured in some soils through the use of phospho-
germs housed in humus, but with no claim of plant food
content. By housing numerous kinds of bacteria in a suit-
able medium, various materials, containing plant food ele-
ments are released by their action, which would not be
affected by only one kind of bacteria.
Departments of Agriculture are often asked to give
opinion as to the value of advertised soil bacteria. It is
manifestly impossible to pass judgment on these bacterial
inoculents, the value of which depends upon the number
SOILS AND FERTILIZERS 21
of virile organisms, adapted to the soil to which they are
to be applied, whose mission is to transform the organic
and mineral elements in the soil so as to render them
available for the plants to be grown.
It is also evident that this kind of soil building agency
must be judged by an entirely different standard from
that of fertilizers. No chemical test would reveal anything
as to the value of these bacteria. The laws regulating the
manufacture and sale of commercial fertilizers do not touch
the subject of soil inoculents. This phase of practical
soil improvement has not been reduced to an accepted
science. When unbiased investigation and adequate dem-
onstration fix a standard for soil inoculation value there
should be legal regulation of the sale of soil bacteria the
same as for commercial fertilizers.
So far no attempts have been made to supply carbon in
available form to plants, an element that constitutes an
average of 40% of the structural parts of plants. During
the carboniferous age, when the atmosphere was sur-
charged with carbon dioxide, vegetation grew so plente-
ously and of such gigantic size as to prepare the material
for the great coal beds of the world. Prof. Riedel has
demonstrated that artificially supplied carbon dioxide will
produce remarkable results in the growth of plants. No
scheme for commercializing this discovery has been at-
tempted. Organic material operated on by bacteria may
liberate carbon dioxide which passing up through the soil
is absorbed by the leaves. No less an authority on foods
than Alfred W. McCann maintains that the ash of foods,
which is usually passed over as so much unavoidable rub-
bish, contains chemicals which are absolutely essential;
that the mysterious vitamins are but the sum total of cer-
tain mineral elements in food; and their marvelous effects
but the resultant of the chemical reactions set up by these
mineral elements. May it not be that the carbon of plants
and the ash of foods have not received consideration com-
mensurate with their importance?
Burzelius classes all organic matter in the soil as humus.
Humus is formed by the decay of vegetable matter-veg-
Humus is a generic term applied to a group of substances,
which form the organic matter of the soil.
22 DEPARTMENT OF AGRICULTJFRE
They range in color from a brownish yellow to a blackish
brown, or black, and are non-volatile. They are probably
all composed of carbon, hydrogen, and oxygen.
While Mulder regarded humus as the'anost exclusive
source of the organic constituents of plants, Liebig, and
other chemists of today, regard the atmosphere as capable
of affording an abundant lipply of all these substances.
The atmosphere consists of nitrogen and oxygen gases,
vapor, carbonic and nitric acids, and ammonia. Plants
can appropriate these from the air only by the roots or
foliage. Leguminous plants extract nitrogen from the air
by way of the roots through bacterial action in the nodules
on the roots. The air comes in contact with the roots by
the soil being porous, which is aided by cultivation. Some
soils are closer than others, and some growths have a
tendency to impact the surface with turf-Bermuda grass,
as an example-while other plants have a loosening effect-
as the cocklebur.
Humus performs a useful function in retaining moisture,
furnishing a habitat for bacteria, and in holding potash,
soda, lime, and magnesia, and in preventing them from
being washed out of the soil.
Scientists have divided peat into several varieties. The
words, peat, muck, humus, marsh, bog, and heath are often
used synonymously, but they are far from being synony-
mous. Peat is partially carbonized vegetable matter.
There are various kinds of peat due to the vegetation of
which; is composed and the conditions under which the
fornmXon has taken place, and the age of the deposit.
The materials contributing to peat beds are many, in-
cluding both land and aquatic vegetation, such as ferns,
mosses, grasses, roots, weeds, twigs, leaves, shrubs, etc.,
found in the presence of water. In an advanced stage of
decomposition combined with more or less dirt, shells, etc.,
it is called muck. Peat may be humus, but humus is not
Dr. William Whitney, Chief, Bureau of Soils, Depart-
ment of Agriculture, Washington, D. C., under date of
August 6th, 1920, says:
"It is impossible to make definite statement as to the
availability of the nitrogen contained in peat. Its am-
SOILS AND FERTILIZERS 23
monia content at any time is low, and is considered as very
slowly available, hence commonly classed as a low-grade
nitrogenous fertilizer, especially when compared with tank-
age and dried blood. Recent observations, however, seem
to indicate th4theavailability is increased by proper pro-
motion of bacterial- growth by inoculation, as by the use s
of barnyard manure with the peat. In connection with
mineral nitrate, however, it promises to be of value in
supplying a slowly available supply of nitrogen after the
readily soluble nitrates have been used up."
Organic materials have been extensively used to secure
nitrogen but such sources as cottonseed meal, blood tank-
age, fish-scrap, ground bone, etc., are now used as feed
stuffs and the price is so high as to be almost prohibitive
as material for fertilizer. It is often desirable to derive
a part of the nitrogen from an organic source, so that
there will be a supply of nitrogen during the entire period
of growth. The present sources of supply of nitrogen-
led by the nitrate beds of Chile-are apt to remain our
dependence unless atmospheric nitrogen should be produced
cheaply enough to compete with them.
As a filler for commercial fertilizer, peat, when properly
prepared has no superior, and few equals now in use by
fertilizer manufactures. It has three distinct points in
its favor over other fillers extensively used: (a) it fur-
nishes a splendid habitat for bacteria; (b) it is an ideal
absorbent of excess ammonia that might escape from other
ammoniates used in the formula, holding them in as avail-
able condition as any other nitrates; (c) being a Aumus,
it has moisture-retaining quality that is much in its favor ,
aiding drouthy soils and helping bacterial action.
The fact that peat properly conditioned before being
dug has an appreciable amount of plant food, is well
established. That this can be made available by bacterial
action, is also beyond question. That fertilizer manufac-
turers should be allowed to claim credit in their brands
for the ammonia in peat when used as a filler wquld seem
to follow. But there are two very essential things which
must be known before the legitimacy of this claim can be
determined. First, was the peat of proper quality and in
24 DEPARTMENT OF AGRICULTURE
rper condition before being dug? Second, does the process
.. treament after being dug, in preparing it for the ferti-
r liw-trade, damage it as a fertilize? ta
4ir dmiuown these two things t the pest is of g
ried, d, ea baa with mimer-
ous groups of germs, the value is tiad 'qBt iu. On
the other hand, if the peat is of poor quat, raw, and
undecomposed, is dug and dried to 10% moisture by blast
Sfurnace-what have you? As another propositkim if the
peat is all right as to quality, and is dried by oil blast fur-
eaace to 15% moisture, what is the result?
.-. Dr Thomas, of the Earp-Thomas Cultures Corporation,
x" ork, says, under date of Oc "-h, 1920: "When
St of the ligneous variety is dried out with excessive
heat in a short space of time it becomes very insoluble."
The ligneous variety is not the best for fertilizer. Dr.
John N. Hoff, industrial and agricultural chemist, New
York, says under date of Oct. 22nd, 1920: "The effect of
drying peat in direct driers with oil fuel does not reduce
the availability of the ammonia. *
As peat will gasify and burn at about 414 degrees Fahren-
heit, you will realize that the partly dried peat will not
permit final drying much above the average temperature
Under date of December 27, 1920, he writes: "It has
been my observation that the average peat will begin to
gasify between 300 and 400 degrees Fahrenheit and there-
fore is likely to burn, which will produce ash with con-
sequent loss of organic matter."
The heat-drying process is now carried on without the
blast coming in contact with the peat, the degree of dry-
ness is thus made optional. If the peat is rendered too
dry for bacteria to live in it, the inoculating can be done
by the farmer-the easier if he does his own mixing.
SOILS AND FERTILIZERS 25
F THE farmer would adopt and practice home mixing
of fertilizer it Iuld save millions of dollars to the
producers of :.. -country. Not that .fertilizer mixers
make exorbitant profits, but they must charge enough to
cover their enormous overhead expenses, to which must be *
added the freight on the dirt used as a filler. It is good
business, economical, educational, and a mark of individual,-
ity, to buy your own ingredients, and do your own comZi
pounding. The elements composing complete fertilizer cai ..
be purchased separately. They should be bought b. -m-
munities in bulk, handledd on a cash basis if possible.
The reasons why the majority of farmers buy complete
fertilizers are : (a) the ease with which it can be bought
on time; (b) the desire to shun the work of buying sep-
arately the different elements and mixing them; (c) the
lack of self confidence.
The following articles constitute a fairly good equipment
for home-mixing fertilizer:
1-A screen with 3 meshes to the inch, 5 ft. long, and
2 ft. wide.
2-A shovel with square point.
3-An iron rake.
4-A pair of large scales.
5-A tight barn floor, or hard, dry, smooth ground.
6-A heavy wooden pestle for crushing big lumps of the
The screening should be done first-all lumps crushed
and screened again. Then spread out the most bulky of
the element in layers-one on another-beginning with
the most bulky constituent. Shovel the heap several times,
until no streaks appear. Then sack or box and keep in dry
place until ready to use.
There are compatible and incompatible elements. Just
as a physician who knows nothing of chemistry or phar-
macy might write a prescription that could not be com-
pounded because of incompatibility of certain chemicals
included, so, in mixing the constituents of a complete fer-
tilizer, it is necessary to know the action of the different
ingredients upon each other. To mix potash salts with
Thomas slag is likely to result in hardening, and render
26 DEPARTMENT OF AGRICULTURE
it necessary to crush and pulverize before using. Certain
arnmoniates contain iron, and if mixed with acid phosphate
will lose a considerable portion of its available phosphoric
acid. Sulphate of ammonia should not be mixed with
Thomas slag and Norwegian nitrate Cyanamid should
not be mixed directly with sulphate of ammonia, but
should be mixed as per directions. Basic slag should not
be mixed with sulphate of ammonia, blood, or tankage,
as the lime affects these materials and releases ammonia.
Lime should not be mixed with guano as it causes nitro-
*gen to escape. Sulphate of ammonia should not be mixed
with basic slag nor quicklime with acid phosphate. To
Smix lime with superphosphate renders the phosphoric acid
less soluble-therefore, less valuable.
SOILS AND FERTILIZERS
Tl HE following table shows how to find the quantity of
Each material necessary to make 1,000 pounds of fer-
tilizer of any desired analysis:
Aalble Available Phosphoric Acid Av
Available ------- Available
Percentage Nitrogen From 14% From 16% Potash from
Required From Nitrate Acid Acid Sulphate
of Soda Phosphate Phosphate of Potash
S67 lbs. 71 Ihs. 63 lbs. 19 Ibs.
133 lbs. 143 Ib. 125 lbt 38 lbs.
200 1b. 214 Ih. 188 Ibs. 58 Ibs
4 267 lbl. 286 lbM. 280 lb.. 77 lbs.
5 333 lbs. 357 lbs. 313 Ibs. 96 lbs.
a 400 Ibs. 420 lbs. 375 bs. 115 lbs.
7 467 lb. 500 lb.. 438 lbs. 135 lbs.
533 Ibs. 571 lb. 500 IbM. 164 Ibs.
600 Ib. 643 lbs. 563 lb. 173 b1.
1 667 Ib. 714 lhs. 625 Ib. 192 Ibs.
If a formula 4-7-5 is wanted, it would mean 267 pounds
of nitrogen, 500 pounds of 14o phosphate, and 96 pounds
of sulphate of potash, making a total of 863 pounds,
which contains the same amount of plant food as 1,000
pounds of 4-7-5 complete, ready-mixer, commercial fertilizer.
To make out 1,000 pounds add dry loam as "filler."
A. B. Ross has shown that neither in the Pennsylvania
nor Ohio long-time experiments did nitrogen prove profit-
able in fertilizers for rotations containing clover. Those
experiments showed that plants got nitrogen from else-
where than legumes or from commercial fertilizers, as the
amounts taken from the soils exceeded the amount stored
by the legumes and the amount contained in the applied
Legume bacteria are not the only soil organisms that
can make direct use of nitrogen from the air. A group
known as the azotobacter have this power. Perhaps there
are others. This is mentioned as a suggestion to those
who may get results which differ from what they had a
right to expect from regular methods.
28 DEPARTMENT OF AGRICULTURE
What we all like is a "cut-and-dried" formula for doing
things, and we do not like the formulas to disappoint us
when being put to the test. But in the use of any for-
mula herewith given, it should be borne in mind that much
depends upon the mechanical condition of the soil, the ele-
ments of available plant food already in the soil, and other
contingencies, as to the result that will follow.
If you use complete fertilizer you might have a formula
Nitrogen ......................... 4%
Available phosphoric acid............. 6%
Potash ............................ 8%
Ammonia ......... ............... 5%
Phosphoric acid ..................... 8%
Potash ............................. 5%
Phosphoric acid .................... 7%
Potash ........................... .. 8
And use from 1,000 to 1,500 pounds per acre. Or if you
do your own mixing, the formula might be:
Nitrate of soda .................... 320
Acid phosphate .................... 100
Sulphate of potash .................. 100
Dry loam ............. ........... 100
Stated in percentages:
Available nitrogen ................... 4.8
Available phosphoric acid.............. 7.68
Available potash ................... 5.0
This is taking the 1,000-pound basis. It will need a
thousand pounds to the acre, but 300 additional pounds of
loam should be added to secure a satisfactory mechanical
condition for the fertilizer.
Ammonia ......................... 4%
Available phosphoric acid............. 6%
Available potash .................... 8%
SOILS AND FERTILIZERS 29
Six to eight hundred pounds per acre, applied at time of
Other formulas widely used are:
Nitrogen ..................... 89 pounds
Phosphoric acid ............... 23 pounds
Potash ...................... 102 pounds
Nitrogen .......................... 8%
Phosphoric acid .................... 2%
Potash ............................ 10%
Available nitrogen ................... 5%
Available phosphoric acid............. 4%
Available potash .................... 8%
Nitrogen ............................ 3
Phosphoric acid ................... 8%
Potash ............................. 3%
Nitrogen ........................... 4%
Phosphoric acid ..................... 5%
Potash ............................ 9%
Kainit or muriate of potash should be avoided, as the
chlorine militates against burning well in cigars. The
sulphate form is preferred. Per acre, from 1,000 to 1,500
pounds, preferably given in three equal dressings, just
before planting and at time of first hoeing and, last, from
two to three weeks later.
Fifty bushels of corn per acre takes from the soil 67
pounds of nitrogen, 31 of phosphoric acid, and 80 pounds
Judged by these requirements, if
deficient in the three constituents of
the formula should be:
Phosphoric acid .............
the land is equally
a complete fertilizer
30 DEPARTMENT OF AGRICULTURE
But the following is more often used:
Available nitrogen .................... 3%
Available phosphoric acid............. 7%
Available potash .................... 6%
Cotton is "easy" on land, but the clean cultivation results
in the leaching and washing of the soil. A crop of 300
pounds of lint removes from the soil in lint, seed, stalks,
etc., about 44 pounds of nitrogen, 49 pounds of potash, and
12 pounds of phosphoric acid.
Were all but the lint returned to the land each year, it
would show no signs of exhaustion. The relative quantities
of the various ingredients of cotton fertilizer depends
entirely upon the soil. Cotton can be grown on as great a
variety of soils as any crop of the Southern States. The
following may be used where the soil is already fairly well
Nitrogen ........................... 3%
Available phosphoric acid............. 8%
Potash ............................. 4%
As this plant is a legume and gets nitrogen from the
air, acid phosphate and potash are the chief elements to
use in fertilizing it. The soil should be rich in lime. The
formula should perhaps be 8% potash, and 8% phosphoric
acid, and the amount from 500 to 800 pounds per acre.
However, this is a mere suggestion as it is entirely de-
pendent on whether or not the soil has either of these
elements in abundance; in some soils, a small per cent of
nitrogen should be used.
Ammonia .......... ... ....... 4%
Available phosphoric acid............. 8%
Potash ............................. 4%
Sugar cane should yield from 25 to 40 tons per acre.
SThe amount of fertilizer should be from 600 to 800 pounds
SOILS AND FERTILIZERS 31
Nitrogen ........................... 4%
Available phosphoric acid............. 6%
Actual potash ...................... 8%
Amount per acre, 600 to 800 pounds.
Ammonia ........................... 2%
Available phosphoric acid ........... 10%
Potash ............................ 4%
When the land has an organic soil, such as peat, the
nitrogen can be reduced, and the other elements increased.
From 400 to 500 pounds per, acre is the correct amount.
Ammonia ................ .......... 5
Available phosphoric acid............. 8%
Potash ............................. 3%
Apply 400 to 600 pounds per acre.
Nitrogen ........................... 3%
Available phosphoric acid............. 8%
Actual potash ....................... 4%
Apply 400 to 600 pounds per acre.
In the clay hill counties of Florida, wheat can be grown,
and the best preparation is to follow a crop of cowpeas
that were sown in July and all turned under at the time
of maturity that would best suit the mowing of hay. The
peas should be sown late for the reason that they vine
much better than when sown early. They can be sown in
corn at the last plowing. Should they mature too early
for sowing wheat, they should be plowed under anyway,
and allowed to lie till sowing time.
If the vines are rank, as they should be, when the land
is fertile enough to make wheat, it will take a good two
horse plow to turn them under, and the plow should have
a rolling cutter in front to cut the vines, so that the plow
will not be continually choking. It is impossible to do
32 DEPARTMENT OF AGRICULTURE
much with iron tooth drag in these vines-the teeth will
have to be slanted backward, so as to slide the vines, that
are left uncovered after the land is plowed.
The grain should always be treated for smut before
Clover and grasses for hay or pastures should be fer-
tilized according to the nature of each. Lespedeza is an
excellent legume for general use on dry hills, as pasture,
and, when soil is sufficiently fertile to produce rank growth,
yields good hay. The leading farm grasses of Florida
are Bermuda, Johnson, St. Augustine, and Carpet-others
are coming into use.
Where the soil is adapted to Johnson grass, it is well
nigh impossible to kill it. When a farm is well set to it,
the owner has a Johnson grass farm forever. Bermuda
is also very difficult to destroy. Heavy crops of cowpeas,
velvet beans, kudzu, or sugar cane will shade it and kill
it faster than any other treatment. Carpet grass is easily
destroyed and therefore, is to be recommended for lawn-
making, and also for grazing.
Nitrogen .......................... 2%
Phosphoric acid .................... 8%
Potash ...................... ..... 8%
Good stable manure is the most valuable fertilizing
material for the growing of all classes of vegetables upon
all types of soils. It must often be reinforced with com-
mercial fertilizers. There is not enough stable manure
to supply the demand for general field crops and near
large cities it is inadequate for truck farming-since the
automobile car and truck have superseded the horse in
Stable manure should be well worked into the soil before
planting. The nearer planting time manure is applied, the
finer it should be pulverized.
For asparagus, beets, carrots, cauliflower, celery, cu-
cumbers, egg plants, kale, lettuce, musk-melons, onions,
English peas, peppers, radishes, spinach, squash, and to-
SOILS AND FERTILIZERS 33
Nitrogen ........................... 5%
Available phosphoric acid ............. 7%
Available potash ............ .... 5%
There is no iron-clad formula and this is given as an
"indicator" and guide rather than as a specific from which
there is to be no variation.
Following are two good formulas for fertilizing lettuce.
Use the one which seems to suit your soil and general
conditions best; or if preferred use some other approxi-
1. Ammonia, 5 to 6 per cent.
Available phosphoric acid, 7 to 9 per cent.
Potash, 8 to 10 per cent.
2. Ammonia, 6 to 7 per cent.
Available phosphoric acid, 6 to 7 per cent.
Potash, 6 to 7 per cent.
Apply from 1,500 to 2,000 pounds per acre, and while
the crop is growing top-dress with about 150 to 200 pounds
of nitrate of soda per acre. It requires about three pounds
of seed to sow an acre, or one ounce to every 250 feet of drill.
Baskets for shipping can be obtained from the vegetable
crate manufacturers in any section of the State.
This is one crop which requires plenty of potash ferti-
lizer, and you will find it will pay to broadcast the field
with a ton of kainit, harrowing it in. Next lay the field
off in furrows, the width you wish the rows apart, which
is from four to five feet, setting the plants about three
feet apart in the row; using 1,500 pounds of fertilizer in
these furrows which should analyze as follows: Ammonia,
5%; available phosphoric acid, 4%; potash, 9%. Cover
it well and see that you get it well mixed with the soil.
Ammonia ......................... 3%
Available phosphoric acid ............. 7%
Potash ............................. 7%
34 DEPARTMENT OF AGRICULTURE
Or, per acre-
Bone meal ......................... 1700
Muriate of potash ................... 300
Or, per acre-
Nitrate of soda................ 100 pounds
Acid phosphate ............... 400 pounds
Muriate of potash ............. 100 pounds
Cabbage needs a very rich soil. Where stable manure
cannot be secured, 1,000 to 2,000 pounds of fertilizer may
be used in something of the following proportion:
Nitrate of soda................ 300 pounds
Bone meal ................... 500 pounds
Muriate of potash.............. 200 pounds
It should be well incorporated into the soil before
Either of the following formulas for commercial ferti-
lizer are good for celery, and the one which seems best
adapted to the soil and conditions can be used, or any
other approximately similar:
1. Nitrate of soda ................ 300 pounds
Fish scrap .................. 800 pounds
Acid phos., 16% ............... 600 pounds
Muriate potash ................ 300 pounds
Ammonia .......................... 6.9%
Available phosphoric acid............ 5.5%
Potash ........................... 7.2%
2. Nitrate of soda ................ 250 pounds
Dried blood ................... 600 pounds
Acid phos., 13% ............... 850 pounds
Muriate potash ................ 300 pounds
SOILS AND FERTILIZERS 35
Ammonia ........................ 7.2%
Available phosphoric acid............ 5.5%
Potash .......................... 7.8%
During the growth of the crop from one to two tons
per acre of the above may be applied between the rows,
and from two to four hundred pounds of nitrate of soda
per acre as a top-dressing in four equal applications at
about four different times.
From 500 to 800 pounds per acre of a fertilizer contain-
ing 10% of potash, 8% of phosphoric acid, and 3% of
nitrogen would be an average application.
The experienced citrus fruit grower has learned by ex-
perience the kind, amount, and frequency of use, of fer-
tilizer for his grove. The newcomer to a citrus section
should consult growers of long experience in his locality.
Nitrogen plays an important part in the production of
new wood and leaf growth. Excess of nitrogen produces
die-back, which causes the bark to become thick skinned
and puffy. Phosphorus is necessary for the proper devel-
opment of the fruit. Sulphate of potassium is usually
preferable to the muriate as the latter sometimes has an
injurious effect on citrus trees.
Use from one to three pounds per tree for young trees,
according to age, of
Nitrogen ........................... 5%
Phosphorus ....................... 5%
Potash ............................ 3%
Apply in early spring, mid-summer, and in September.
Increase this about a pound a year until the trees are five
or six years old, and begin to bear commercial crops. Then
use three applications per year with
Nitrogen ........................... 4%
Available phosphoric acid............. 8%
Potash ............................. 4%
36 DEPARTMENT OF AGRICULTURE
Apply in early spring, and mid-summer. The fall appli-
cation should be between November 15th and December
15th with the nitrogen reduced to 3% without changing
the other materials.
Trees well bearing from ten years old up should receive
from 15 to 30 pounds per year. Older and heavy-bearing
trees receive from 30 to 75 pounds of fertilizer per annum
where no green crops are turned under, and unless the
trees have a great distance between them green crops
cannot be successfully grown.
Judging by the elements taken from the soil by a citrus
grove the formula of chemical manures per acre of orange
trees, will be:
Nitrate of soda ............. 560 pounds
Superphosphate of lime (16%
soluble phosphoric acid)...... 612 pounds
Sulphate of potash ............ 170 pounds
Obviously, however, this general formula must not be
adopted without reference to specific conditions; it must
be modified to meet the requirements of each particular
case, according to the nature of the soil and the state of
vegetation in the plantation.
When lime is needed for the element calcium, as chem-
ical analysis will show, or to correct acidity, as the litmus
paper test will indicate, apply lime carbonate or hydrate.
SOILS AND FERTILIZERS 37
CITRUS FERTILIZER PROGRAMS
(The Citrus Industry, July, 1932)
Proposed and Issued by Agricultural Extension Service,
University of Florida
Chemical analysis shows that the average Florida citrus
soil (virgin) is low in the essential fertilizer nutrients-
nitrogen, phosphorus, and potassium. Citrus production
has been obtained by adding these elements to the soil from
time to time.
The sources of ammonia fertilizers are divided into two
general classes, namely inorganic and organic.
Of the inorganic ammoniates, sulphate of ammonia and
nitrate of soda have been most extensively used and have
given satisfactory results in both field and experimental
The other sources of ammonia, such as nitrate of soda-
potash, calcium nitrate, urea*, ammonium phosphate, am-
monium nitrate, urea-nitrate of lime, ammonia nitrate-
sulphate mixtures have not been used so extensively as
the first two forms. But when properly applied, field ob-
servations indicate that they may be used with satisfac-
Phosphorus Acid Sources
Superphosphate has been the most commonly used source
of phosphorus acid in ordinary grove conditions. Due to
the relatively low solubility of the untreated inorganic
phosphates their efficiency as a source of phosphorus is
not equal to that of superphosphate.
The organic sources of phosphorus, such as guano, fish
scrap, and steamed bone meal are usually more soluble than
the untreated inorganic forms. The efficiency of the phos-
phate fertilizer is usually in proportion to the available
*Although urea is an organic ammonia, it is made synthetically.
38 DEPARTMENT OF AGRICULTURE
phosphate. These sources may be used when prices and
High grade sulphate of potash has been the most com-
monly used source of potash under average grove condi-
tions, but muriate of potash seems practically as good so
far as it has been tested. Other sources of potash such as
nitrate of potash, nitrate of soda-potash, sulphate of potash-
magnesia, hardwood ashes, and tobacco stems should give
Most citrus soils in Florida are low in organic matter.
Moreover, it is generally recognized that organic matter
increases the efficiency of the fertilizer as well as improves
the quality of the soil. For this reason the college recom-
mends that the grower produce as cover-crop on soil, or
haul into grove at least 2 to 3 tons (dry weight) of coarse
organic matter (grass, litter, legumes) per acre annually.
It is not as essential to add the above amounts (annually)
of organic matter to groves on heavy types or where
cultivation is not practiced.
Fertilizer Application (1)
It is the usual practice to apply fertilizer to citrus ac-
cording to the age and bearing capacity of the trees. This
practice, however, is subject to criticism, because of the
irregular bearing habits of trees, as well as the differences
in size of the trees due to variations in soil, root stocks,
etc. Studies of 150 groves of different ages and varieties
indicate that under ordinary conditions the spread of the
tree or the tree size would be a more correct index of tree
needs than age and bearing capacity. So the fertilizer pro-
grams suggested herein base the rate of application on the
actual tree spread (diameter of top). This amounts to an
annual application of approximately .13 to .16 of a pound
of ammonia, .16 to .18 of a pound of phosphoric acid and
.16 to .21 of a pound of potash per foot spread of tree.
While heavy clay soils have a high phosphate fixing power,
recent studies indicate that the sandy soils of Florida have
a comparatively low fixing power. Therefore, the ratio of
phosphorus to ammonia in the fertilizer used on such
sandy soils could be lower than that for heavy clay soils
without affecting yields. Field measurements indicate that
SOILS AND FERTILIZERS 39
the above ratio compares favorably with the best grove
For a large part of the citrus belt experimental data and
field observations indicate that the most reliable results
can be obtained under general conditions with three appli-
cations of ammonia per year-spring, summer, fall. But
due to the retaining power of the soil for phosphates and
potash there is apparently little to be gained by adding
the phosphoric acid and potash three times per year.
The fertilizer should be applied evenly over the soil sur-
face, as far as the roots extend.
Local conditions, such as moisture, soil type, cover-crop,
variety, root-stocks, etc., play an important part in the
behavior of citrus trees toward fertilizer treatments. There-
fore, the fertilizer programs herein set forth are subject
to local modifications.
The following fertilizer suggestions embody three pro-
grams, namely, a mixed fertilizer program, a materials
program and a modified program, each of which is com-
plete in itself.
40 DEPARTMENT OF AGRICULTURE
Tabulated Fertilizer Programs For Bearing Citrus Groves*
MIXED FERTILIZER PROGRAM (1)
Time of Application* .......Kind and amount of fertilizer mixtures to be applied per
foot of spread (or diameter of top)
SPRING-Jan.-Feb. ........1 lb. mixed fertilizer, 5-6-3, or its equivalent
SUMMER-April-June .... 1 lb. 4-6-8 or equivalent to trees under 10 years of age
1 lb. 4-6-10 or equivalent to trees over 10 years of age
FALL-Oct.-De ........ 1 lb. 4-6-5 or equivalent to trees under 10 years of age
S1... lb. 4-6-8 or equivalent to trees over 10 years of age
MATERIALS PROGRAM (1)
Time of Application**....... Kind and amount of fertilizer materials and mixtures to
be applied per foot of tree spread (or diameter of top)
1/ lb. nitrate of soda or 1-5 lb. ammonium sulphate.
Organic ammonia may be used when justified by prices
SPRING-Jan.-Feb. ........ FOR FURTHER TRIAL BY GROWERS
% lb. nitrate of soda-potash or nitrate of lime, or % lb.
urea-nitrate of lime, or 1-12 lb. urea of equivalent
amounts from other sources.
(a) Repeat the spring application of ammonia, re-
ducing the amount-10-20% where spring culti-
vation is practiced or 20-30% following a heavy
legume cover-crop the previous year.
(b) 1 lb. superphosphate (16%) or the equivalent.
This may be reduced 50% in groves over 20
SUMMER-April-June ..... years old. Other sources of phosphorus may be
used when justified by delivered unit price and
(c) 1-6 lb. sulphate or muriate of potash to trees
under 10 years of age.
1-5 lb. to older trees or trees believed to need
more potash. Other potash materials may be
used in equivalent amounts.
FALL-Oct.-Dec ............Repeat summer application (a) and (c)
MODIFIED PROGRAM (1)
Time of Application** ...... Kind and amount of fertilizer mixtures to be applied per
foot of tree spread (or diameter of top)
SPRING-Jan.-Feb. ........Use spring application in Material Fertilizer Program
SUMMER-April-June ..... 1 lb. 4-8-8 or equivalent to trees under 10 years of age
1 lb. 4-8-10 or equivalent to trees over 10 years of age
FALL-Oct.-Dec.*** ........Same as the summer application.
For trees 1 to 6 years old reduce the amount of the regular fertilizer from 20%
for 1 year trees to 5% for 6 year trees respectively. On heavy hammock soils the
total amount of ammonia may be somewhat reduced.
**With each program of fertilizer practice, apply % to % the amount of the spring
application of ammonia in August or September to nonbearing trees, to trees showing
the need of ammonia, or where a heavy non-legume cover-crop is returned to the soil
the current year.
***The fall application of fertilizer may be reduced, or even omitted in northern
part of citrus belt or where conditions seem to justify the practice.
(1) Where groves are consistently heavy producers, the potash should probably be
increased. On the other hand, the ammonia should probably be decreased on soils high
in organic matter.
SOILS AND FERTILIZERS 41
A Word About Formulas
A standard for designating the ingredients of complete
fertilizers by numerals has been adopted by control officials
and the fertilizer trade. The nitrogen or ammonia is placed
first, the phosphoric acid second and the potash last. The
fertilizer tags of Florida follow this standard, which means
that a numerical formula would mean that the first number
stands for ammonia or nitrogen, the second for phosphoric
acid and the third for potash.
With this understanding, a formula 5-8-3 means that
100 pounds of complete fertilizer contains five pounds of
nitrogen or ammonia, eight pounds of phosphoric acid and
three pounds of potash.
As a ton is two thousand pounds it contains twenty
times as much of each fertilizing ingredient as a hundred
pounds of the fertilizer contains.
To ascertain the number of pounds of each ingredient in
a ton of mixed fertilizer:
Multiply the per cent required by 20.
For instance: In the above formula, 5 multiplied by 20
equals 100; 8 multiplied by 20 equals 160; and 3 multi-
plied by 20 equals 60. Therefore one ton of this mixture
Phosphoric acid ............... 160 pounds
Nitrogen ..................... 100 pounds
Potash ............... ........ 60 pounds
The remainder of the weight is extraneous matter.
To find the quantity of an ingredient needed to supply
the per cent required:
Divide the number of pounds of the ingredients in a ton
by the number of pounds of that ingredient in a hundred
pounds of the material containing it. The result will be
the number of pounds of raw material used to give the
percentage desired in the formula.
42 DEPARTMENT OF AGRICULTURE
If we use acid phosphate containing 16 per cent of
available phosphoric acid, to find the quantity of raw ma-
terial needed to supply the per cent of the ingredient re-
quired we must divide the number of pounds required in
a ton by the 16.
If cotton seed meal is used to obtain the nitrogen the
number of pounds required in a ton must be divided by
6.18, as that is the per cent of nitrogen in a hundred
pounds of the meal.
If we use muriate of potash to finish the formula we
use a material that yields 51 per cent of potash; but we
can count in 1.8 per cent of potash from the cotton seed
meal that we used which would reduce the requirements
of muriate, and we deduct the number of pounds that
has been added by the meal from the number of pounds
to be added by the muriate.
In like manner if the filler that is used contains avail-
able nitrogen the per cent thus added may be deducted
from the cotton seed meal. This is seldom the case, but
it might be so if properly prepared peat is used as a filler.
In the above illustration the use of peat would lessen the
amount of cotton seed meal, which, in turn, would lessen
the amount of potash furnished by the meal. However,
it is not necessary to split hairs over such small discrep-
ancies in proportion. The rules for calculation herewith
given are approximately accurate in results, and entirely
practical but it will show a little over a ton.
To Find the Analysis of a Given Mixture
Suppose a farmer has on hand available materials which
he wishes to use in certain proportions and wants to know
the analysis of the proposed mixture. Take 1,000 pounds
of acid phosphate, 16 per cent; 800 pounds of cotton seed
meal, and 200 pounds of kainit.
One thousand pounds of 16% acid phosphate contains
160 pounds of available acid; eight hundred pounds of meal
contains eight times 618 or 50 pounds of nitrogen.
Two hundred pounds of kainit at 12.5 pounds per hun-
dred contains 25 pounds of potash. The eight hundred
pounds of meal contains 1.8 pounds per hundred, or 14.4
pounds of potash.
SOILS AND FERTILIZERS 43
Therefore the above mixture contains phosphoric acid, 160
pounds; nitrogen, 50 pounds; potash, 39.4 pounds.
To find the per cent of each of these materials in a
ton we divide each by 2,000 with the following results:
Phosphoric acid, 8%; nitrogen, 3%; potash, 2%; formula,
"Converting" element into equivalents:
To illustrate: Ammonia contains 82 per cent of nitro-
gen. Therefore to "convert" per cent of ammonia into
nitrogen multiply by 0.824.
To "convert" per cent of nitrogen into equivalent in
ammonia multiply by 1.214.
Three per cent ammonia multiplied by 0.824 equals 2.47
per cent nitrogen.
Two per cent nitrogen multiplied by 1.214 equals 2.44
per cent ammonia.
To convert ammonia into protein multiply by 5.15; nitrate
of soda into nitrogen multiply by 0.1647; nitrogen into
protein multiply by 6.25; muriate of potash into actual
potash multiply by 0.632; actual potash into muriate multiply
by 1.583; sulphate of potash into actual potash multiply
by 0.541; actual potash into sulphate of potash multiply by
1.85; nitrate of potash into nitrogen multiply by 0.139;
carbonate of potash into actual potash multiply by 0.681;
actual potash into carbonate of potash multiply by 1.466;
chlorine in kainit multiply potash (K20) by 2.33.
In calculating values you simply take the number of
pounds of each ingredient in a ton and multiply it by
the price of the materials used. The ruling price used to
be 4 cents per pound each for phosphoric acid and potash
and 18 cents for nitrogen. But 16% available phosphoric
acid was worth $28.00 a ton purchased for cash in ton
lots at Florida seaports; sulphate of potash, $180; nitrate
of potash, $130.00; sulphate of ammonia, $137.00. (Octo-
DEPARTMENT OF AGRICULTURE
Fertilizer prescriptions are at best founded on conclu-
sions drawn from generalization rather than from positive
knowledge. The chemical composition of the soil and its
mechanical condition should be known but rarely is. The
average composition of the crop to be grown, and the
relative amounts of the three principal elements-nitrogen,
phosphoric acid and potash-which a given crop of a given
yield will extract from the soil, should be known, and
whether or not the crop is leguminous.
Whether lands are sand, clay, hill, bottom, drained or
wet, been in pasture or cultivated, plowed deep or shallow,
crops rotated or not, etc., these items should be known;
the results of past experience in fertilizing land under
consideration; yellow foliage indicating lack of nitrogen;
shedding of fruit indicating need of potash. Where flavor
is an item potash should be used in the sulphate form.
With pineapples and tobacco carbonate of potash and cotton
seed meal are adapted.
All fertilizer tags should specify the sources from which
the ingredients are derived and the per cent derived from
each source. They should also state the kind of materials
used to make up the filler and the percentage of each material
used, and pounds of available plant food per hundred.
Protein, fat, sugar, starch, etc., are animal food terms and
do not belong in fertilizer formulas.
SOILS AND FERTILIZERS 45
We Learn How to Speed the Work of Priceless Soil Bacteria
BY J. SIDNEY CATES, in The Country Gentleman
T HE good old word "tilth" as applied to soil needs to
come back into general use. It serves to denote a
condition of the land and to set forth an ideal of
management covered by no other term. During the past
generation both biological and chemical sciences have piled
up a mass of information about the soil, and we are begin-
ning to see the seemingly inert land we walk over and plow
in a new and romantic light.
Keeping it in fettle is something more than the mere
mechanical task of tillage. In fact, the German word for
tilth, gare, is frequently interpreted as meaning fermenta-
tion. It is an interpretation which fits well, for we know
that a good soil is seething with life, pouring forth invisible
gases that leaven it and fine its texture, and leaving behind
by-products ideal for plant food. And, ranked as a chem-
ical laboratory, no learned doctor with his retorts and
bottle-arrayed walls can duplicate or even approximate the
reactions that Nature, working through this life-filled
upper eight inches of a plowed field, carries on night and
day uninterruptedly year after year.
These midget chemists of the land, the bacteria, play the
major role in promoting tilth. In teeming hordes they are
present. They often number more than three billion to
the ounce of soil, and under many conditions algae, molds
and protozoa are equally abundant. The total microscopic
life in an acre of land has been calculated as weighing from
500 to 700 pounds, or approximately the equivalent weight
of livestock that a good pasture will carry. And while
the role that this soil life plays is so complex that it will
probably take more generations of close study before the
full activities going on under the surface of the land are
clearly understood, a few broadly fundamental facts have
already been brought to light.
In the first place, it is clear that soil life is necessary for
true fertility-that is, for power of the land to produce
DEPARTMENT OF AGRICULTURE
crops. Not only must this germ life be abundant, but it
must be in a healthy well-nourished state and actively
multiplying, in order that the land may have that loose,
crumbly texture taken as a good omen by the eye of every
Tireless Nitrogen Gatherers
Bacteria, for the most part, subsists on organic matter
in the land. Not only does this teeming soil life break
down added vegetable matter, producing or setting free
mineral salts upon which crops directly feed, but one large
group of soil bacteria functions in the nitrogen-gathering
role probably with as great benefit to soil fertility and
tilth as the better-known nitrogen-fixing germs which grow
on the roots of leguminous plants. A legume crop will con-
tain from 100 to 200 pounds of nitrogen. Probably half
of this comes from nitrogen compounds already in the
land, and the remainder is gathered in from the air by the
aid of nitrogen-fixing germs with which the roots of the
legume are inoculated. We hear much of the importance
of having a legume crop in the rotation. We hear, how-
ever, but little of the other and greater source of nitrogen
supply in our soil. This other great source is through the
action of bacteria feeding on the dead vegetable matter.
One leading American bacteriologist recently gave me
the estimate that the quantity of nitrogen fixed in soils by
these independent organisms varies from ten to forty
pounds a year an acre. The large quantity is often to be
found when a plentiful food supply in the form of organic
matter is made available for them to feed upon. These
germs, while fixing annually a smaller quantity of nitrogen
than is gathered in by a legume crop, more than over-
come this handicap through working all the time, and in all
soils, while the legume rarely ever occupies the land as
much as half the time, and usually only one year in the
four-year rotation; and on many farms is not planted at
It has been the experience of mankind for ages back that
vegetable matter turned into the land made it more pro-
ductive. Since the establishment of our own experimental
institutions in this country, an abundance of data has been
accumulated, all showing that organic matter in the land
takes the leading upbuilding part. But now we know that
this organic matter is not used directly by crops; that it
SOILS AND FERTILIZERS
must first be broken down by soil life. With the exception
of nitrate, acid phosphate and the various potash salts,
plants take no fertilizers in the form we put into the soil.
Not only are bacteria necessary in preparing the raw food
we supply in form for plants to consume, which is a mineral
form, but the bacteria themselves, thus fed, gather vast
quantities of nitrogen, the most expensive of all plant foods.
The quantity they gather seems to bear a close relation
to the provisions we make for their food supply. And this
conclusion puts the problems of the tilth of the land in a
Soil life also shows considerable preference in its diet.
It has long been observed that stable manure in many cases
exerts an effort on crop growth out of all proportion to
the plant food it contains as shown by analysis, and that
the same is true of green matter turned into the land in
the early spring. Studies during recent years have shown
that both these substances make wonderful feeding for the
bacterial flora of the soil, causing a sharp upward spurt
in soil-life activity. In pot experiments, a small quantity
of green matter chopped into one soil pot almost always
caused a sharp leaping ahead of the plant it grew as com-
pared with another plant in a similar pot where the soil
was not so treated. It seems to me there is considerable
evidence to justify us in planning cropping systems in
so far as soil maintenance goes, with a view to feeding
plenty of vegetable matter to the soil bacteria, and if a
goodly quantity of this bacteria food we offer is in a
succulent green state, there is plenty of evidence that it
will be all the more relished.
In the Middle West, farmers who turn a sweet-clover
sod very early in the spring before much growth has
been attained, yet while this growth is in a very succulent
stage, note that a fat yield of corn follows. Over in the
Connecticut Valley in New England, farmers have found
that it pays to sow timothy between rows of cultivated
crops in late summer, and to turn this feeble early spring
growth in time to plant another tillage crop the next year.
In New Jersey the truckers turn a winter cover crop of
rye or vetch or alsike clover before it has attained enough
growth to make an impressive showing. Yet they have
found that this means a saving of fertilizer bills, and a
great boost to the tillage crop which follows. A small
quantity of this succulent material greatly stimulates soil
bacteria. And it is the bacteria which make for tilth in
48 DEPARTMENT OF AGRICULTURE
We passed through a state of mind not so long back
when common observation of farmers, out of line with
some half-understood but supposedly wholly elucidated
theory, was ranked as mere superstition or old women's
tales. Science is today more tolerant and less cocksure
than it used to be. In fact, some of the hypotheses on which
learned men are now working seem more strange and
weird than what were ranked as superstitions of by-gone
times. Our thought with reference to soil problems seems
itself to be in a healthy state of ferment.
One bacteriologist, in discussing the role of this micro-
scopic life in promoting tilth in soils, called what we know
as poor land "raw," and likened it unto a green cheese, both
of which he said were prepared for real food, one for hu-
mans by the ripening action of enzymes in the milk and
the other for plants by the ripening action of bacterial
New Light on Rotations
Take the case of the explanation of why rotation of
crops is beneficial. The farmer has long known that by
rotation he could keep the land in better tilth, and that
he could keep both himself and the land more regularly
employed. Not long back, rotations were claimed by scien-
tists to keep up yields better than single cropping through
the fact that different kinds of plants remove plant-food
elements from the soil in different proportions, and that
by changing from one crop to another, the soil supply of
plant food was kept more evenly balanced. This point
of view has long since been pretty well abandoned. Then
for a long while we looked upon rotations as being a means
of keeping up fertility through growing periodically a sod
or legume crop to boost the vegetable matter and nitrogen
supply, and beyond this shifting crops is a means of keep-
ing both land and labor the more continuously employed.
Now we are finding that different crops act on the soil
bacteria in different ways. Legumes aside from being
host plants to what we term symbiotic bacteria growing
on their roots, the bacteria being fed carbohydrates by
the plants and in turn feeding the plants with nitrogenous
material-aside from this well-known fact, it has been
proved that legume crops specially favor the development
of bacteria in general in the soil. Fortunately most of our
cultivated crops seem friendly toward soil bacteria. Some
few, notably mustard, have been observed to be distinctly
SOILS AND FERTILIZERS 49
detrimental to the nitrifying and other desirable soil bac-
Wheat does not seem to leave the bacterial flora of the
soil in as good condition as corn or potatoes. European
agriculture has pretty well settled down on a system which
does not include the growing of wheat oftener than once
in two years. Fortunate it is that corn does not seem to
have a very detrimental effect on soil bacteria.
50 DEPARTMENT OF AGRICULTURE
SULPHUR FERTILIZATION TO HELP SAVE
AMERICAN SOIL FERTILITY
BY COURTNAY DEKALB,* in Manufacturers Record
THE shortage of fertilizers not only caused an almost
prohibitive increase in their price, but it became fi-
nancially impossible for a large proportion of our
farmers to purchase fertilizer at all. Everywhere it was
used in greatly reduced amount. Although American agri-
culturists are far behind the progressive farmers of Europe
in fertilization, the curtailment of our customary supplies
at a critical moment, when men were keenly awakened to
the need of superior effort to produce foods, threatened to
precipitate a national calamity. An alarming decrease in
the yield per acre was seen throughout all those portions
of the country where the farmers had become educated to
use fertilizers. At the same time the Food Administra-
tion posted in every conspicuous spot throughout the land
the impressive slogan: "Food Will Win the War." Thus
was the menace of serious weakening in our power to fight
It was during this period of need that the writer, re-
sponding to the national call for means to increase the
food supply, directed attention to the remarkable results
that had been obtained in France and in other countries
by means of sulphur fertilization. This method of aug-
menting the yield had been tested by a number of the
United States Experiment Stations. Extraordinary bene-
fits had been reported from long-continued tests in Oregon,
Utah, New Jersey, Kentucky, and elsewhere, but no wide
public notice had been taken of the fact. The masses do
not read the wonderful bulletins issued by the Agricultural
Experiment Stations; the facts recorded mainly reach the
people at the second hand through the agricultural papers,
or tardily, in isolated cases, through observation of the
results obtained by progressive neighbors who are fully
awake to the great service the United States Department
of Agriculture is doing through its systematic investiga-
*Mr. Courtenay DeKalb, distinguished engineer, chemist and technical expert, is
particularly well qualified to discuss this subject. He has had practical experience in
his professional capacity as an investigator in various places in this and other coun-
tries, and has been an educator and voluminous writer on scientific matters. He is
an honorary member of the Geographical Society of Peru, a member of the American
Institute of Mining and Metallurgical Engineers and of the American Chemical Society.
SOILS AND FERTILIZERS 51
tions in scientific agronomy, and who read the literature
issued from the Bureaus in Washington and the co-ordi-
nated Experiment Stations in the several States.
A first article published in the Manufacturers Record,
showing enormous increases in yield-100 per cent to 1000
per cent in alfalfa (Bull. 163, Oregon Agricultural Experi-
ment Station), 300 per cent in peas (P. J. O'Gara, A. S. &
R. Agricultural Experiment Station, Salt Lake, Utah), 40
per cent in kaffir corn, and the like-aroused such keen
interest that it proved necessary to follow it by a second
article in which the reasons for the efficacious results ob-
tained with sulphur applied as a fertilizer were set forth in
detail. These explanations were later confirmed by Dr.
O'Gara and others in articles also appearing in the Manu-
At a time of dire national need it meant a great deal
to be shown that it had been proved to be possible to in-
crease the yield of cereals 25 per cent to 100 per cent, even
if limited to somewhat restricted areas to which sulphur
fertilizer could be distributed economically. It was a vital
matter to be able to double and treble the acre-yield of
beans and peas at a period when the Government was con-
tracting for shiploads of beans in the Far East, and was
anxious lest the bean-line to the soldiers in training camps
and on the plains of France should be interrupted. More-
over, while the importations of Rio Tinto pyrite, formerly
our main dependence as a raw material for making sul4
phuric acid with which to prepare acid phosphate, had
been reduced for want of bottoms to a few thousand tons
per annum, and while nearly the total supply of domestic
sulphur melted from the deep wells of the Union, Free-
port and Texas Gulf companies on the Gulf of Mexico was
required to make acid for explosive manufacture, it was
pointed out that Nature had provided superficial deposits
in Culberson County, Texas, in Wyoming, in Utah, in Ne-
vada, and elsewhere in the West, where elemental sulphur
was associated with gypsum and lime and lesser amounts
of magnesia, making an ideal material to function as a
As a result of these and other public announcements, sul-
phur fertilizer is taking a position as one of the most use-
ful substances for increasing the yield of many crops.
Sulphur companies East and West are distributing it in
varied forms, and the agricultural experiment stations in
52 DEPARTMENT OF AGRICULTURE
at least twenty States are investigating the extent of its
adaptability and a large number have already made favor-
able reports. In some of the States, with intent on the
part of legislators to protect the farmer against the adul-
teration of fertilizers, laws had been passed that limited
the sale of fertilizers to those products that contained only
a few of the necessary plant foods. Changes in these laws
are being demanded. Intelligent farmers will not tolerate
laws on the statute books that put a bar to progress.
It is curious to read statutory definitions of what plant
foods are, and to find that only three are mentioned. One
of America's greatest agricultural chemists, Dr. Charles
H. MacDowell, President of the Armour Fertilizer Works,
Chicago, and President of the National Fertilizer Associa-
tion, in an address before the Chicago Section of the
American Chemical Society, September 23, 1921, said:
"For a long time it has been considered that these three
elements, nitrogen, phosphorus, and potassium, were the
only plant-foods necessary to supply ordinary soil. Re-
cent years have.brought about some change in this belief.
Certain crops seem to demand some other element that is
ordinarily not abundant in all soils. For instance, only
within the last few weeks it seems to have been definitely
proven that the tobacco plant must have a certain amount
of magnesia in its food-supply in order that it may prop-
erly cure. It is claimed that the super-excellence of the
Hawaiian pineapple is due to the manganese present in
those soils. Are we, then, to believe that only these two
plants are peculiarly susceptible to such conditions? Can
we safely assume that every plant has a similar necessity?
Most of the experiment stations of the country are now
studying the effect of sulphur, both elemental and in
compounds, on various crops. Oregon has shown surpris-
ing results on legumes with sulphates (chiefly with sul-
.phur fertilizer, now standard practice among alfalfa grow-
ers in Oregon-C. DeK.) New Jersey applies elemental
sulphur for reaction within the soil itself. What a research-
field is open to the agriculturist and to the chemist! This
further leads us to the question of the balanced ration for
plants. * *
"These problems must be solved if this country of ours
is to maintain itself in the front rank or as a leader of the
nations of the world. Our tendency has been recently to
commercialize our science. Our agricultural science must
SOILS AND FERTILIZERS 53
be national, must be removed from politics and commercial
influences. We must realize that, as a nation, we must get
more from our soil. Our scientists must solve these vital
questions in the near future or the coming generations will
find their food-supply restricted either as to quantity or
variety to a point where degeneration of the race sets in
and conditions similar to those now obtaining in the Orient
will be in effect here."
A similar lesson was enforced by Dr. W. S. Landis in
an address at a joint meeting of the Honorary Scholastic
Societies at Columbia University, New York, on Decem-
ber 7, 1921. He shows that the problem is world-wide, but
that America, curiously enough, is one of the most back-
ward of all countries in practical agriculture. This is a
matter of grave moment when we consider that already
we have begun to import staple foods-meat, potatoes,
even grains-in large amounts, and that more than half
our total population is now crowded into cities, and from
a food standpoint is non-productive. As a nation we have
persisted in the primitive viewpoint held by the pioneer
when he was subduing a virgin continent. We still have
an incorrigible tendency to cultivate acreage on the grand
scale, instead of striving to increase the output per acre.
We go on as if we still had unlimited areas of soil that
had never been stirred by the plough. Our farmers strain
their finances to buy ever more elaborate and costly imple-
ments, but they balk at the purchase of plant-food to renew
the wasting asset of soil fertility.
Says Dr. Landis:
"The higher yields of even the oldest European farms is
largely due to the use of fertilizer, along with more care-
ful and intense cultivation. * But fertilizers are hardly
used in the United States. In 1919 on 359,000,000 acres of
cultivated land there was used less than 7,000,000 tons of
fertilizer, not counting barnyard manure, or less than an
average of 40 pounds per acre. The most concentrated of
these fertilizers carried less than 20 per cent of plant food,
and the average of all less than 14 per cent. Just think:
On the average less than 6 pounds of plant-food is added
to the acre of tilled land, and that the wheat harvested
from that same acre (straw excluded) carried off 34
pounds of plant-foods."
Dr. Landis might have pointed out that the crops har-
vested here and abroad are in direct proportion to the
54 DEPARTMENT OF AGRICULTURE
amount of fertilizer used. The average return from Amer-
ican wheat fields from 1905 to 1913 was 14.6* bushels per
acre. In France it was 20.2 bushels, and the average con-
sumption of fertilizer was 111 pounds per acre; in Ger-
many the yield was 30.9 bushels with an average of 207
pounds of fertilizer; in Great Britain the figures were 33.4
bushels and 244 pounds respectively. Assuming a price
for fertilizer of $40 per ton to the farmer and a selling
price of $1 per bushel for the wheat, the British farmer
wins an extra $18.80 per acre over the American farmer's
average, at an extra cost of $4.14, giving him a net gain
of $14.66 per acre.
This is but a single instance of the great possibilities
lying before the American farmer which he can utilize
as soon as he is led to realize that, with practically the
same labor, one acre, when he goes about it rightly, will
yield a larger profit than two under his present neglect
of the advantages of fertilization. If this were borne in
upon his consciousness so that he should begin to purchase
the kinds of fertilizer needed in proportion to the amounts
employed by the British farmer, he would call for seven
times as much as is used today, and the capacity of the
existing fertilizer plants would be utterly unable to meet
the demand. Certain it is, the farmer must begin to
utilize fertilizers on a proper scale very soon or he will
be swamped and the nation will become dependent on
foreign countries for food to an alarming extent. We can-
not go on indefinitely removing five times as much plant-
food from our soils as we return to them.
Mr. MacDowell was right in insisting that it is im-
perative to provide growing plants with a balanced ration.
That means not only that a proper amount of available pot-
ash, nitrogen, and phosphorus shall be incorporated into
the soil, but that the lack of sulphur, or lime, or magnesia,
or iron shall be made good, in accordance with the special
requirements of different crops. Dr. L. W. Erdman, of
the Iowa Agricultural Experiment Station, in "Soil
Science" for December, 1921, (p. 433), says: "Recently
many soils have been found to be deficient in sulphur, one
of the essential plant-foods, and sulphur requirements of
certain crops are apparently much greater than formerly
*In 1921 the average had dropped to 12.7 bushels per acre.
SOILS AND FERTILIZERS 55
Sulphur fertilization is specially important for plants
that normally contain large amounts of protein, for all
proteins hold sulphur as an essential constituent. C. O.
Swanson and R. W. Miller, of the Kansas State Agricul-
tural College ("Soil Science" Vol. III, No. 2, p. 139), says:
"That sulphur is an element essential to crop production
has long been recognized by both botanists and agrono-
mists. Sulphur is indispensable in the formation of plant pro-
teins, and because of the intimate connection of protein
compounds with life processes, it probably serves physi-
ological functions in the formation of compounds which
do not contain sulphur." A shortage of sulphur means les-
sened crops. This applies with special emphasis to legumes,
including alfalfa, clover, beans and peas.
It is evident that the role of sulphur in the soil is com-
plex. It has been pointed out (P. E. Brown and H. W.
Johnson, "Soil Science," Vol. 1, No. 4, p. 339) that "the
total sulphur content, alone, of a soil will not show the
sulphur available for plant-growth. The sulfofying or sul-
phate-producing power of the soil must also be ascertain-
ed." In other words, there are effects produced upon the
bacterial life in the soil that are of the utmost value, and
the mere presence of sulphates, or the introduction of sul-
phates in combination with potash, ammonia, or acid phos-
phate, is not equivalent to the bacterial oxidation of sulphur
in the soil in contributing to the healthy growth of plants.
Not only does this action stimulate the sulfofying bacteria,
but the ammonifying and the nitrogen-fixing bacteria as
The production of sulphuric acid in the soil when free
sulphur is present, both directly and by indirect reactions,
liberates potash and phosphorus in available form from
the soil particles. It is on account of these reactions that,
as two of our ablest agronomists have said, for permanent
soil fertility, the sulphur supply for crops must be con-
sidered. (Brown and Johnson, loc. cit.). It is also note-
worthy that, although small amounts of sulphur are brought
down in the rains (normally about 7 pounds per acre yearly,
and slightly more in regions where large quantities of
coal are burned in manufacturing) the losses by drainage
have been found to exceed in most cases the sulphur de-
rived from this source, and the amount removed from the
soil by a large number of common farm crops is very much
greater. For example, a normal crop of sugar beets, re-
56 DEPARTMENT OF AGRICULTURE
moves 12 pounds of sulphur, alfalfa 26 pounds, and cabbage
There is no doubt that sulphur is of the greatest value in
fertilization to stimulate a healthy growth of plants, to
provide them with an essential plant-food, and to render
available the plant-food constituents in the soil. In this
respect its function is unique. The American farmer must
not only work his acres but make his acres work, and
he must make them work to the limit. This can be done
only by strong fertilizer, and he must bear in mind the
importance of maintaining the balanced ration. He must
provide all the foods needed, and not omit any that will
insure healthy crops and maximum returns.
SOILS AND FERTILIZERS
SOIL ANALYSIS NO GUIDE TO FERTILIZATION
BY E. J. KINNEY, in Southern Agriculturist
FARMERS frequently ask their experiment station to
analyze a sample of soil from a certain field and on
the basis of the analysis to recommend the exact
fertilizer needed to produce a certain crop. They are often
very much disappointed, and sometimes a bit angry, be-
cause the station refuses to make such recommendations.
Soil analyses have been of considerable value to agri-
culture. They have given us a wide knowledge of the
character of the various soils of the country, and have
made it possible to make general recommendations in re-
gard to the necessary treatment of these soils in order to
maintain permanent fertility. As a guide to fertilization
in particular instances, however, they have little value.
A chemical analysis gives us fairly accurate data on the
total amount of plant food in the soil. It tells us whether
or not the supply of phosphate or potash is sufficient to
produce good crops under good systems of management
without buying commercial forms of these mineral elements
of plant food. It also tells us whether the soil is acid or
alkaline, but it does not show us the crop-producing capacity
of a certain soil at a particular time.
The samples used by a chemist are of necessity so small
that the inaccuracy in a very careful analysis, by a skilful
chemist, may be greater than the amount of plant food
contained in a very heavy application of commercial plant
food. A field that has been reduced to temporary low
productive power by heavy cropping or bad farming may
show as much total plant food as another field capable
of producing a big crop. For example, we may raise five
crops of corn in succession on a naturally good piece of
land. At the end of that time the ability of that field to
produce corn will be much lessened. Yet a chemical analy-
sis may show practically no difference in the amount of
plant food present between this field and one lying beside
it that has been in pasture for five years.
This is hard to believe; but such are the present limi-
tations of the chemical analysis. The weight of an applica-
tion of fertilizer is so small in comparison with the great
DEPARTMENT OF AGRICULTURE
weight of the surface foot of an acre of land (about 4,000,-
000 pounds) that the use of a ton per acre may be unde-
tected in an analysis. If in addition to the analysis, how-
ever, the soil expert has a good knowledge of how the land
has been cropped and treated, he can usually make recom-
mendations for fertilizer treatment that will meet the re-
quirements fairly well.
Take, for example, the question of fertilization for dark
tobacco on the lands of Western Kentucky. A chemical
analysis shows these soils to be rather low in phosphate,
but rich in potash. If they are handled well-that is, if
crops are rotated, legumes grown, some manure used and
possibly lime, the soil expert may recommend the use of a
phosphate fertilizer only. He knows that the phosphate
supply is too small to give maximum yields even under the
best system of soil management. Potash, on the other
hand, will become available in sufficient amounts for all
requirements on well managed soils; and if legumes are
grown often in the rotation, the nitrogen supply may be
adequate. In case of tobacco, however, which gives rela-
tively large returns per acre, a liberal supply of nitrogen
is needed for best results and he may recommend the use
of some nitrogenous material. If the land has been cropped
fairly hard, it usually pays to use a complete fertilizer. The
expert will recommend the amounts to apply almost wholly
on the cropping practices of the past.
SOILS AND FERTILIZERS 59
SAVING MONEY IN PURCHASING FERTILIZER
BY R. W. RUPRECHT, in The Florida Grower
EVERYBODY is interested in ways to save money; none
more so than the farmer who must make every dollar
count if he expects to come out ahead of the game.
One of the ways a farmer can save money is in the careful
purchase of fertilizers. There are three different and yet
closely related ways by which you can cut down your fer-
tilizer expenses. These are as follows:
1. Pay cash.
2. Buy co-operatively.
3. Buy high grade fertilizers only.
The idea of paying cash for what you buy is gradually
spreading all over the country and into all lines of business.
The cash and carry grocery stores, I believe, were the first
ones to show the savings that could be made by getting
away from a credit business. It is only within the last
two or three years that the fertilizer trade has made a
special effort to get its business on a cash basis. A few
years ago over 80 per cent of the fertilizer trade was on
a credit or time basis. Just what the figures are today I
cannot say but judging from reports I have had from sev-
eral fertilizer companies the percentage has been lowered.
All fertilizer companies will give a substantial discount
if you pay cash for your fertilizer. Some companies are
offering as much as 13 per cent discount if you send them
a check with your order, or 10 per cent for cash for 10 days
from invoice. Others give discounts varying from 5 to 8
per cent. Have you ever figured out how much you would
save if you took advantage of these discounts? Let us take
an actual case and figure out the saving.
Discounts Offer Big Savings
I have a price list showing a price of $42 per ton for
a 5-7-5 fertilizer. Suppose you are buying 10 tons of this
formula. This would make a total of $420. However, if
you send a check along with your order you would only
have to send them $378.00, making a saving of $42, which
is 10 per cent of $420.00. Quite worth while, is it not?
60 DEPARTMENT OF AGRICULTURE
Nor is this all you would save. If you paid six months
after date of your invoice you would get a bill for $420,
plus 8 per cent interest on this amount for 6 months, or
$16.80, so you would be paying $436, instead of $378, the
cash price. I know that for a good many farmers it would
be pretty hard to lay their hands on four or five hundred
dollars to pay their fertilizer bill. Those of you who can-
not find the money should go to your banker and borrow
the money from him. True, you will have to pay him 8
per cent interest on the money but you will still be saving
We now come to the third class of farmers-those to
whom the local banker will not lend the money. What I
am going to say may sound cold-blooded but it is the
truth nevertheless. If your own banker who knows you
and your farm and your farming methods does not feel
that he can lend you money safely, the fertilizer com-
panies have no business to sell fertilizer to you on time.
One of the chief, if not the chief reason, for the hard
times that the fertilizer industry has just been through
was due to this very practice, namely of extending credit
where it had no business doing so.
Do you not realize that all you who pay your fertilizer
bill are also paying the bill of the dead beat and crook
who orders his fertilizer but never intends to pay for it?
Some people would have you believe that all farmers are
honest. But farmers as a class are just like other groups
of people, be they clerks or college professors or what not.
Some will do wrong.
Probably all of you are familiar with the cash and carry
grocery store and know that they sell goods at a lower price
than the old time grocer where you went in, ordered your
goods and said "charge it." The cash and carry stores have
to pay just as much for their goods when they buy from
the wholesaler as does the other grocer where you say
charge it. Why can they undersell him then? Simply be-
cause they have no bad bills and no bookkeeping to do. The
very same thing applies to the fertilizer trade. Even now
they allow you a substantial deduction for cash as I pointed
out before, but this will be largely increased if they ever
get to the point where they do nothing but a cash business.
Co-operate in Buying
We come now to the second way in which you can save
money in buying your fertilizer: Buy co-operatively. By
SOILS AND FERTILIZERS 61
buying co-operatively I mean buying through some farm-
ers' organization or just a group of neighbors getting to-
gether and sending their order in as one. The amount
you can save by thus lumping your orders will depend
largely upon the size of your order. Most fertilizer com-
panies will quote you a lower price on a full carload of
one brand of analysis than they will on single ton orders.
A still lower price will be quoted if you can get together
a total of 100 tons, preferably of one analysis. The cut
in price will vary from $4 per ton up. Why can the fer-
tilizer companies afford to give you this extra cut? Simply
because they can save about that much in taking care of
your order. You can readily see, I think, that it takes less
time to look after one large order than a dozen small less
than carload shipments. In many cases the less than car-
load shipments have to be hauled to the freight station
while the carloads can be loaded into the cars right from
the bagging machine. Hauling costs money as you all
know, hence the lower prices for goods that do not have
to be hauled. Another saving is made in bagging the fer-
tilizer. It is considerably cheaper to keep a bagging ma-
chine running on a single formula all day or half a day
than to have to keep changing. Each change means a cer-
tain amount of lost time because you cannot start bagging
a different formula until the machine has been cleared of
the one you have been bagging. This lost time will vary
in different factories but will, I believe, average pretty
close to $5 or $10 per day, maybe more. Another saving
that the fertilizer companies make in handling orders is in
storage charges. It gives them an opportunity to use up
raw material as it is received without going to the expense
of storing it in their warehouse. All these savings are
passed on to farmers when they buy co-operatively.
Going now to the third way of saving on your fertilizer
bill: Buy only high analysis goods.
Our last legislature passed a bill which will compel you
to live up to this advice whether you want to or not. The
bill states that no mixed commercial fertilizer sold in the
state shall contain less than 14 units of available plant
food. I am rather glad they did this though it is going
to make some of the farmers rather disgruntled when they
find they cannot buy their favorite 2-8-2 formula. But
let me show you that in place of grumbling they ought to
give the legislature a vote of thanks.
62 DEPARTMENT OF AGRICULTURE
According to one of the latest price lists, a 2-8-2 fer-
tilizer costs $30.50 per ton. The same price list also con-
tains a fertilizer analyzing 3-9-3 at $35. This would make
a 3-12-3 fertilizer cost about $38. Now let us do a little
figuring. Three tons of the 2-8-2 fertilizer would contain
6 units of nitrogen, 24 of phosphoric acid and 6 of potash,
and at $30.50 per ton would cost you about $91.50. Two
tons of the 3-12-3 formula would give you 6 units of nitro-
gen, 24 of phosphoric acid and 6 of potash, the same as
the 3 tons of 2-8-2 and would cost you at $38 per ton $76.
Subtract $76 from $91.50 and you get $15.50. In other
words, you can get the same amount of plant food in the
two tons of 3-12-3 as you get in three tons of 2-8-2, and
you save $15.50 and the freight on one ton of fertilizer.
After the first of January, 1926, you will be unable to
purchase the 2-8-2 fertilizer. To take its place I would
recommend that you try the 3-9-3 which will, I feel sure,
give you just as good results at a substantial saving. See
how kind the legislature was. It is forcing you to save
The Difference In Fertilizers
Why is it that there is such a big difference in the price
of these two fertilizers? Let us look at a typical formula
for these two analyses and see what we can see:
110 pounds nitrate of soda.
267 pounds cotton seed meal.
1,000 pounds acid phosphate.
84 pounds sulphate of potash.
539 pounds filler.
320 pounds nitrate of soda.
267 pounds cotton seed meal.
1,388 pounds acid phosphate 17 per cent.
125 pounds sulphate of potash.
Fourteen Standard Formulas for Florida
The first column gives the per cent of nitrogen, the
second the per cent of available phosphoric acid and the
third the per cent of potash in the fertilizer.
SOILS AND FERTILIZERS 63
The crops shown after each formula indicate some of
the crops for which it is best suited, but there may be other
crops for which it is suited. For some soils or under some
conditions some other formula than the one indicated might
give better results. Consult your county agricultural agent
if in doubt as to what formula to use.
3-9-3-General field crops, such as cotton, corn and pea-
4-8-4-Sweet potatoes. Strawberries on rich soil.
5-7-5-5-8-5--General truck crops, particularly water-
melons, cantaloupes and Irish potatoes. Strawberries on
5-5-5-Celery, lettuce and cabbage.
4-8-3-Peas, beans, growing pecan trees, citrus nursery
stock and young grove trees.
4-8-6-Sweet potatoes, Irish potatoes, tomatoes, sugar
cane, bearing pecans and peaches.
5-7-3-General truck crop or cabbage on clay soils.
3-8-5-Tomatoes on soils rich in organic matter.
Also summer and fall citrus applications.
3-8-8-3-8-10-Citrus fall and winter application.
2-8-10-Citrus fall and winter application on rich soils.
4-8-8-Citrus in spring, tomatoes and strawberries.
6-6-4-General truck and cabbage on poor soil.
In the one case you have a fertilizer containing 500
pounds or 21/2 bags of filler of little or no value to your
plants, yet for which the fertilizer people had to pay. In
the other case you have a fertilizer containing only materials
supplying plant food.
It cost the fertilizer company just as much to mix the
low grade formula as the high grade. All of the operating
expenses are the same for both formulas. As you are get-
ting six more units of plant food in the high grade formulas
your cost per unit is less. For example, say it cost $3.50
per ton to mix these goods. In the case of the 2-8-2 this
means about 30 cents for each unit of plant food. In the
case of the 3-12-3 it means only 20 cents per unit. There-
fore it pays to buy high grade fertilizer.
In buying high grade fertilizers remember that we have
in Florida a list of 14 so-called standard fertilizers. All
of these are high-grade formulas and we believe that there
is a formula on this list that will prove satisfactory for
all crops raised in this state. If you and other Florida
64 DEPARTMENT OF AGRICULTURE
farmers will stick to this list of formulas when you order
fertilizers we will eventually lower the price of fertilizer.
Why? Because the fewer number of formulas the ferti-
lizer companies have to handle the smaller the expense.
If you had about 50 different lots of feed in your barn,
each of which had to be kept separate and apart from its
neighbor, and if in feeding your live stock you had to take
a little from each of the 50 lots, you know it would take
you longer than if you only had five or six different lots.
The fertilizer companies are in the same position, only with
them the longer time means more money for time is money
when you are dealing with men who get paid by the hour.
At the 1928 fertilizer conference in Shreveport, the fol-
lowing 11 fertilizer formulas were adopted for recommen-
dation in Texas, Louisiana and Arkansas: 12-3-0; 10-4-0;
8-4-4; 7-5-5; 8-7-0; 12-2-2; 12-3-3; 10-4-4; 10-4-2; 8-4-6;
and 12-0-4. The figures indicate the per cent of the
three plant foods contained in the mixture; the first repre-
senting phosphoric acid; the second, nitrogen; and the
In a general way, it may be suggested that the 12-3-0 and
10-4-0 formulas be used on clay and loam soils, and sandy
soils with clay subsoils for such crops as corn and cotton.
Where the soil is known to be deficient in potash and the
crop is cotton, either 12-3-3, the 12-4-4 or the 10-4-2 mix-
ture is usually applied. The formulas 7-5-5 and 8-4-6 are
for the truck grower, while the 8-7-0 mixture is for cane
on alluvial land. The 12-0-4 formula is supposed to supply
legumes with the required plant food.
SOILS AND FERTILIZERS
CITRUS FERTILIZER EXPERIMENTS
BY S. E. COLLISON, in Bulletin 151 of the State University
T HE judicious use of commercial fertilizers in the
orange grove has been one of the important prob-
lems confronting the Florida citrus grower. In the
expense involved and the effect upon the tree and fruit,
this problem ranks as of equal importance with any of the
other operations in the as ayin harpsting,
running or cultivation At the time when the work reported
r tis buietin was begun, practically no experimental
work in this line had been carried out in the state. The
existing knowledge of the effects of the various fertilizers
in use was entirely the result of the practical experience
of the growers themselves and was of a more or less con-
flicting nature. In order to obtain accurate knowledge of
the effects of various fertilizers over a comparatively long
period, the experimental work discussed in this bulletin
was undertaken. A young grove was located on Lake Harris,
about three miles from Tavares, in Lake county, and used
for the experiment. The piece of land was selected with
special reference to protection from cold, adaptability to
citrus culture and uniformity of type of soil. It is gen-
erally considered that the influence of the fertilizer treat-
ment given citrus trees may extend over a period of several
years after that particular treatment has been discontinued.
In order to eliminate this disturbing factor from the ex-
periment it was deemed advisable to begin with young
trees. Accordingly, one year-old budded trees, all of the
same variety, especially selected with regard to uniformity
of size, and all from the same nursery, were used in the
work. They were set out in January, 1909, three-quarters
of a pound of bone meal being given each tree.
Plan of Experiment
The objects of the experiment were to determine the
effects of various fertilizers upon the chemical composition
of the soil, upon the growth and composition of the trees
and upon the fruit. The effects of lime and other alkaline
materials, and of various cultural treatments upon the soil
and upon the trees were also objects of study. To sup-
plement the work in the grove with fertilizers, a number
66 DEPARTMENT OF AGRICULTURE
of soil tanks were made use of on the horticultural grounds
of the Experiment Station.
Plan of Experiment
The grove was divided into 48 plots of ten trees each.
These trees were Valencia Late on sour stock, and were
set 15 by 30 feet. The diagram in Figure 1 shows the
relation of the plots to each other. The fertilizer and
other treatment given these forty-eight plots is shown in
Table 1. A standard formula consisting of 5 per cent
5 13 21 29 37 45
4 12 20 28 36 44
6 14 22 30 38 46
3 11 19 27 35 43
7 15 23 31 39 47
2 10 18 26 34 42
8 16 24 32 40 48
1 9 17 25 33 41
Fig. 1.-Diagram of plots in the ten year fertilizer experiment.
ammonia, 6 per cent phosphoric acid, and 6 per cent potash,
was used. In the fall this was changed to 21/2 per cent
ammonia and 8 per cent potash, the phosphoric acid re-
maining the same. The standing mixture consisted of sul-
phate of ammonia, acid phosphate, and high grade sulphate
of potash. As shown in Table 1 this mixture was varied
for different plots by substituting other sources of the three
essential elements for those in the standard mixture. The
standard mixture was used at first at the rate of 2 pounds
per tree three times a year. This amount was gradually
SOILS AND FERTILIZERS 67
increased so that at the end of the experiment the "stand-
ard" plots were receiving an application of six pounds in-
stead of two.
TABLE 1.-FERTILIZER MIXTURES USED
An application of two pounds per tree was taken as the standard
Ammonia, 5 per cent., from sulphate of
Standard formula Phosphoric acid, 6 per cent., from acid
(for young trees) phosphate.
Potash, 6 per cent., from high-grade sul-
phate of potash.
Variations from the Standard
Plot 1. Half the standard.
Plot 2. Standard.
Plot 3. Double the standard.
Plot 4. Four times the standard.
Plot 5. Phosphoric acid and ammonia increased by one-half.
Plot 6. Phosphoric acid and potash increased by one-half.
Plot 7. Ammonia and potash increased by one-half.
Plot 8. Phosphoric acid and potash decreased by one-half.
Plot 9. Phosphoric acid and ammonia decreased by one-half.
Plot 10. Ammonia and potash decreased by one-half.
Plot 11. Standard and finely ground limestone.
Plot 12. Standard and air-slaked lime.
Plot 13. Standard and mulch.
Plot 14. Standard.
Sources of Nitrogen
Plot 15. From nitrate of soda.
Plot 16. Half from nitrate of soda, and half from sulphate of ammonia.
Plot 17. From dried blood.
Plot 18. Half from sulphate of ammonia, and half from dried blood.
Plot 19. Half from nitrate of soda, and half from dried blood.
Plot 20. From cottonseed meal.
Plot 21. From cottonseed meal. (With ground limestone).
Plot 22. Half from cottonseed meal, and half from sulphate of ammonia.
Plot 23. Half from cottonseed meal, and half from nitrate of soda.
Sources of Phosphoric Acid
Plot 24. From dissolved boneblack.
Plot 25. From steamed bone.
Plot 26. From steamed bone. (Double amount).
Plot 27. From Thomas' slag. (Nitrogen from nitrate of soda).
Plot 28. From Thomas' slag. (Double amount. Nitrogen from nitrate
Plot 29. From acid phosphate. (Potash, 7% per cent in June, 7% in
October, and 3 in February).
Plot 30. From acid phosphate. (Nitrogen from nitrate of soda. Potash
from hardwood ashes).
68 DEPARTMENT OF AGRICULTURE
Plot 81. From acid phosphate. (Standard).
Plot 32. From dissolved boneblack.
Plot 38. From floats.
Plot 34. From floats. (Double amount).
Plot 85. From floats. (Four times amount).
Plot 86. From floats. (Four times amount. Nitrogen from cotton-
Sources of Potash
Plot 87. From low-grade sulphate.
Plot 88. From muriate.
Plot 89. From high-grade sulphate of potash. (With ground lime-
Plot 40. From kainit.
Plot 41. From high-grade sulphate of potash. (Standard).
Plot 42. From nitrate of potash. (Balance of nitrogen from nitrate
Variations from the Standard
Plot 48. No fertilizer.
Plot 44. Standard.
Plot 45. Standard and mulch.
Plot 46. Standard and clean culture.
Plot 47. Nitrogen from dried blood. Clean culture.
Plot 48. Nitrogen from nitrate of soda. Clean culture.
TABLE 2.--COMPOSITION OF GROVE SOIL, ANALYSIS OF
I Soil I Subsoil
Insoluble matter ..................... 49.09 94.81
Volatile matter ....................... 2.55 1.71
Nitrogen ............................. .08 .018
Phosphoric acid ...................... .10 .09
Potash ............................... .047 .025
Soda ................................. .184 .115
Lim e ................................. .13 .17
Magnesia ........................... .14 .09
Magnesia oxide .................... .. .10 .14
Ferric oxide ......................... .98 .96
Aluminum oxide ...................... 2.80 2.40
Sulphuric oxide ...................... trace trace
Carbon dioxide ....................... none none
I P205 N
1st foot ................ ...... ...... .12 .080
2nd foot .............................. .10 .015
3rd foot .............................. .09 .018
4th foot .............................. .09 .012
5th foot .............................09 .009
Plots 46, 47 and 48 were cultivated during the entire
year. Plots 13 and 45 were mulched with a mixture of
forest leaves, grass, etc. The remainder of the grove was
cultivated up to the rainy season (about June 1), and then
a cover crop allowed to occupy the land until in September,
when it was either turned under or cut for hay and the
SOILS AND FERTILIZERS 69
stubble plowed under. During the early years of the ex-
periment this cover crop consisted of beggarweed. The soil
finally became too acid to support a good crop of the beg-
garweed, and was at first supplemented with cowpeas, and
later on with velvet beans.
TABLE 3.-NITROGEN AND PHOSPHORIC ACID IN SOIL
A B C D E F G Ave.
N .029 .040 .033 .033 .037 .030 .028 .033
P205 .09 .12 .08 .11 .12 .10 .09 .10
N .018 .0181 .0151 .020 .019 .018 .016 .018
P205 .09 .12 .08 .09 .011 .08. .08 .09
The effects of the various treatments on the trees were
measured by taking at regular intervals the diameter of
the trunks six inches above the bud. Notes on the size,
general appearance and character of growth of the trees
were taken from time to time.
Composition of Soil
The soil on which the grove is located is a rather coarse
reddish sand of the hammock type, verging on high pine,
and rather dry in character. At the time that the trees
were set out composite samples of the soil (0.9 inches)
and of the subsoil (9-21 inches) were taken and analyzed.
In one place in the field samples of the first five feet
were taken and the phosphoric acid and nitrogen con-
tained in the samples were determined. These analyses
are given in Table 2. Samples of the soil and subsoil were
also taken in seven different places in the field and analyzed
for phosphoric acid and nitrogen. These analyses are
given in Table 3. They show that the soil over the field
was of a fairly uniform composition. The analyses of this
soil as a whole indicate that it is somewhat above the
average in fertility as compared with citrus soils in gen-
Leaching of Fertilizer
In order to supplement the work with fertilizer in the
field, soil tank experiments were begun on the Station
grounds. By this means it has been possible to more close-
ly measure and control conditions than where the work
TABLE 4.-LOS OF NITROGEN FROM SOIL TANKS
Sulphte of Nitrate of Drid Blood
July 13.. 774 63 74.11 85 2, 72.4 305 1,47 7327 1,96
Ag 23... .... 1,18 72,93 159 1132 61,14 15.3 4,16 69.11 5,68
Sept, ... 4,66 627 639 2034 40,79 33,28 11,98 57.13 17,24
Nov 2.... 18,69 8,46 7849 12,40 2207 3,41 54.21 16,59 5922 2905
Jan, 8......... 8,12 73 10.35 1326 24,15 3544 9,35 49,87 15,80
Mrch 12.... 37,37 5,72 64.64 813 2,56 2159 10.59 2,06 47,81 4,13
April 13.... 3,91 98.09 6,05 346 5 0 1604 43 84,75 ,
June 10.... 37,37 10,14 87.95 1, 11.8 4,87 i20,95 2,10 82,65 2,48
July 16 ....... 9,64 1 10.96 7,94 7.29 18,10 1,99 118,02 2,41
Aug. 23.... ..... 6,43 1025 ..5 7,2 ..... ..... 11802 ..
Oct 21..,, 18,6 9 124,75 2,92 3,46 88452 4,72 18 13533 1,17
April 1... 37.7 ,5 161.46 .52 42 121,65 4,78 171,72 .72
July 14... 37,7 1,61 159.85 1,0 238 119.28 1,95 .27 171,45 ,16
Aug 9 .... ..... 197 2 ..... 156.6 ..... ..... 208 ....
Oct. 31.... 18.69 2.3 213,38 1, 2.17 13,16 1,39 22 227,28 ,11
Jan. 3........ 1,72 21166 .80 43 17273 ,25 16 227,12 ,07
Jan, 24......... ,6 211,09 ,27 .2 172,44 17 ,27 26,85 ,12
Feb, 11......... 59 21050 .28 ,84 171,60 48 ,32 22653 ,14
Mar, 6.... 37,37 .79 24708 .8 .93 8 ,54 ,34 263.57 ,15
Aug, 8.... 37,37 2,33 28212 .94 425 24116 205 27 300,66 ,10
Oct. 10.... ..... 3,12 279,0 1.11 120 2996 50 ..... 3086
Oct, 2 ....18.69 .... 279 ... 239.6 ..... .25 .3,41 ,08
Dec. 21......... 22 29542 .81 22 25642 ,92 41 318,69 ,14
Ju, 6......... 228 13 .77 1.52 25,90 ,59 ,5 318,44 ,08
Jn, ....... 2,0 29110 ,6 1. 25327 ,6 52 31792 ,16
April 5.., 37,37 1,49 28960 .51 86 52.41 ,34 ,45 317,47 ,14
May 17......... 1.02 288.58 .35 .. 5. 312,41 . 317.47 ..
SOILS AND FERTILIZERS
has been conducted on the scale necessary in field experi-
ments. Accurate estimates of the losses of fertilizing ma-
terials in the drainage water under different systems of
fertilizing and the effect of long continued use of fertilizers
on the soil have been possible. In this way much interest-
ing light has been thrown upon the question of the capacity
of the average sandy Florida soil for retaining the ferti-
lizing ingredients added to it and which of these materials
are most subject to leaching.
The tanks were constructed of heavy galvanized iron,
painted inside and out with a chemically-resistant paint.
Each tank had an inside diameter of 5 feet 31/4 inches,
with a maximum depth of 41/4 feet, and a surface area of
one two-thousandth of an acre. As shown in the diagram,
the bottom of the tank slopes to one side, where there is a
strainer opening into a two-inch tin-lined iron drainage
pipe, the length of which is a little over 4 feet. Four such
tanks open into a central collecting pit as shown in Figure
3. Under the ends of the drainage pipes entering at the
four corners of the pit were placed large galvanized cans
for collecting the drainage waters. These cans were coated
on the inside with paraffine to prevent any chemical ac-
tion of the drainage water upon the metal. The collecting
pit, which is about 8 feet square inside, is built of brick,
with a concrete bottom, and is covered. The soil tanks
were sunk in the ground to within a few inches of the
tops and were filled with soil to within 3 inches of the
rims. The soil used was a rather coarse, gray sand of
high hammock type. It is described by the Bureau of Soils
as Norfolk sand. In filling the tanks a layer of quartz
pebbles was first placed over the sloping part of the bottom
in order to provide adequate drainage and to prevent the
soil from sifting through the strainer and filling the drain-
age pipe. Above the layer of pebbles was placed 45 inches
of soil. In excavating for the tanks the soil was removed
in layers. First a 9-inch layer was removed and placed at
one side by itself. Then the soil was removed in one-foot
layers, each foot being kept separate from the remainder.
The last foot of excavated soil was placed in the bottom of
the tank, then the remaining sections ending with the top
9 inches. Thus the soil rested in the tank as it was in the
original state. Each layer of soil was well packed as it
was placed in the tank, the same weight of dry soil, 8,625
pounds, being used in each. The tanks were then exposed
to natural conditions, the drainage water leaching through
the soil being collected from time to time as it became
72 DEPARTMENT OF AGRICULTURE
necessary, and analyzed. This treatment was continued
for a period of 10 months during which time the soil re-
ceived no fertilizer, the results obtained representing the
losses of plant food from a bare, unfertilized soil. The
results show that by far the greatest loss of plant food
falls on the nitrogen of the soil. The thorough aeration
which the soil received when the tanks were filled would
lead to more rapid nitrification of the soil organic matter
and thus to somewhat larger losses of nitrogen in the drain-
age water at first, than would occur under natural con-
ditions. Allowing for this factor, however, the losses of
nitrogen still remain very large. During the 10 month
period a loss of nitrogen equivalent to over 800 pounds
nitrate of soda per acre was noted. The losses of potash
and phosphoric acid were much smaller, in fact, almost
negligible. The loss of potash per acre amounted to about
14 pounds, and phosphoric acid to about a half pound.
These figures show that these two elements of plant food
are locked up in the soil in relatively insoluble forms which
become only slowly available. At the end of this period of
10 months, an orange tree was placed in each tank and
fertilized with a fertilizer of the same formula as that used
in the grove experiment. The trees in all the tanks received
the same amounts of phosphoric acid and potash in the
form of acid phosphate and high grade sulphate of potash,
the source of nitrogen only being varied. The trees in tanks
1 and 2 received sulphate of ammonia, the tree in tank 3
nitrate of soda, the tree in tank 4, dried blood, the same
amount of actual nitrogen being used for each tree. The
same amount of fertilizer as was used in the grove was
applied to each tree three times per year. The results of
the analyses of the drainage water collected from these
tanks from time to time are given in Table 4. These figures
indicate the extent to which the nitrogen of the three
materials used leaches through the soil. These losses are
stated here in percentages of the total amount of nitrogen
applied less the amounts lost on preceding dates. For
example, the table shows that on November 22, 1911, the
drainage water from the nitrate of soda tank contained
an amount of nitrogen equivalent to over 54 per cent of the
total nitrogen which had been applied up to that date,
less the quantity of nitrogen already leached out up to the
same date. In other words, the percentage of loss for
each date was figured on the amount of nitrogen still re-
maining in the soil at that date, and not on the total amount
which had been applied.
SOILS AND FERTILIZERS 73
Loss of Nitrogen
A study of the table brings out a number of interesting
and important facts. It will be noted that while the loss
of nitrogen varies with the material used, the percentages
lost with all three materials increase from the beginning
up to November 22, and continue large until August, 1913.
For the period from July 13, 1911, to July 17, 1913, 41
per cent of the sulphate of ammonia applied to the soil
leached through and was lost in the drainage water; 72.5
per cent of the nitrate of soda, and 38.3 per cent of the
dried blood were lost. This interval of about two years
represents a period during which the trees were becoming
established and when the root system was small and
occupied but a small portion of the soil. Consequently,
much of the fertilizer was not utilized and as a result
leached through the soil and was lost. The fact that the
losses became smaller as time went on indicates that the
larger root systems were able to utilize more and more of
the fertilizer. The table also brings out important dif-
ferences in the behavior of the three different sources
of nitrogen in the soil. It will be noted that the largest
loss of nitrogen occurred with the nitrate of soda, the
losses from the other two sources being considerably less.
The larger loss of nitrate of soda is explained by the fact
that this material is very readily soluble in the soil mois-
ture and that the soil has very little if any power to retain
or fix nitrogen in the nitrate form. Consequently, if the
soil is moist and the rainfall is sufficient to more than
saturate the soil the nitrate of soda is immediately dis-
solved and much of it is carried below the range of the
plant roots. Dried blood and sulphate of ammonia differ
from nitrate of soda in their behavior in the soil.
The nitrogen in these materials is not available for
plants until it is changed to the nitrate form through the
agency of various soil bacteria in the process known as
nitrification. In its original form the nitrogen of dried
blood is not readily soluble in the soil water, and conse-
quently very little is lost in the leaching process until
nitrification occurs. In this change the organic nitrogen
of the blood is changed first to ammonia, then to the
nitrite and finally to the nitrate form, when it becomes as
readily soluble as the nitrate of soda and is leached out
as readily. Nitrification of the dried blood is a gradual
process, extending over a period of time which may be
of several weeks' duration, depending on soil conditions.
TABLE 5.-LOSS OF POTASH BY LEACHING
Tank Tank 3 Tank 4
Sn ero e
Sam 0 0 0 0 0 0 0 0
9~ a ;1 ai i ii i u" i k
Aug, 23 ...
April 13 ...
June 10 ...
July 16 ....
Oct. 31 ....
SOILS AND FERTILIZERS 75
Because of this, some of the nitrogen of dried blood, or for
that matter, any similar organic material, will remain in
the soil a considerably longer time and be available to the
crop over a longer period, than nitrate of soda. This is
especially true where heavy rains occur after the latter
has been applied to the soil.
The behavior of sulphate of ammonia in the soil is dif-
ferent from either of the two materials already discussed.
While this substance is readily soluble in the soil water
the soil has the power of fxing or absorbing at least a
portion of the ammonia, thus preventing it from leaching
away. This takes place through chemical means and is
common to all soils. Very sandy soils can absorb only a
small amount of ammonia; loam and clay soils are able
to absorb much larger quantities, due mainly to the clay
content of these soils. Therefore, when sulphate of am-
monia is applied to the soil at least a part of the ammonia
is absorbed by this clay present and fixed in a form which
is not readily washed out. This ammonia must be changed,
through the agency of the nitrifying bacteria of the soil,
to the nitrate form. Then it gradually becomes available
to the plant and, of course, is then subject to leaching.
These facts account for the smaller loss of nitrogen as
noted in the table, from the soil receiving sulphate of am-
monia as compared with that receiving nitrate of soda.
It should be remembered that the three sources of ammo-
nia here discussed were used side by side, in the same equiv-
alent amounts, on the same type of soil and under identical
conditions so far as these could be brought about in the
experimental work. Accordingly, the behavior of each of
these materials in the soil as compared with the others
may be taken as strictly comparative not only in this ex-
periment but under all usual conditions where they are
used. The actual amount of each which might be lost in
the drainage on different types of soil and under varied
conditions would in all probability differ more or less from
the results given in the table. However, the fact that
nitrate of soda, for instance, leaches through to a much
larger extent than sulphate of ammonia, would hold true
under all ordinary conditions. The important facts brought
to light in the experimental work here described regard-
ing these nitrogenous materials and which have a practical
application in grove fertilization are as follows: Nitrogen,
the most expensive ingredient of fertilizers under normal
conditions and usually the element most deficient in Flor-
76 DEPARTMENT OF AGRICULTURE
ida soils, is the element which is lost in the largest amounts
The various sources of nitrogen differ greatly in their
tendency to leach out of the soil, much more of the nitro-
gen of nitrate of soda than of sulphate of ammonia being
lost in this way.
The greatest losses take place when heavy rains occur
soon after an application of nitrogenous fertilizers.
These losses decrease to a great extent as the trees be-
come older and more of the soil becomes permeated with
Loss of Potash
Table 5 shows that a considerable loss of potash has
taken place. The figures in the potash column represent
the average losses for three soil tanks. The losses for the
first two years are small, after which they increase consid-
erably. This would indicate that during the first period
part of the potash applied was absorbed by the soil, but
that after the second year the soil had reached its maxi-
mum capacity for holding the potash and became saturated,
so to speak, so that succeeding applications were not ab-
sorbed to any extent.
It is well known that practically all soils have some
power to retain soluble potash. Sandy soils exhibit this
capacity in the least degree, while heavy clay soils will ab-
sorb large amounts. The power of a soil to fix or absorb
potash depends largely upon the presence of certain sili-
cates which are associated with the clay present. When
absorbed by the soil, watersoluble potash assumes a form
which is not easily leached out by water but which is still
generally regarded as being more available to plants than
the potash combinations originally present. Since Florida
soils as a general rule contain very little clay their power
to absorb potash is limited. In the work here described it
was found that at the end of four years about 30 per cent
of the potash applied had leached out, the remaining 70
per cent being used by the trees or absorbed by the soil.
In bearing groves the loss by leaching would undoubtedly
be under rather than over the 30 per cent found here.
SOILS AND FERTILIZERS 77
TABLE 6.-INCREASE IN PHOSPHORIC ACID CONTENT OF SOIL
PsOs P20, Increase Increase
Plot Source of in in in in Acid
Phosphoric Acid Plot Check Total Soluble
1...... Acid phosphate.............. 2859 2633 226 200
2...... Acid phosphate.............. 3601 3002 599 480
3...... Acid phosphate.. ........... 4532 3449 1083 850
4...... Acid phosphate.............. 4750 3037 1713 1660
5...... Acid phosphate.............. 3701 3037 664 750
6...... Acid phosphate.............. 4080 3449 631 720
7...... Acid phosphate .............. 3513 3002 511 450
8...... Acid phosphate .............. 3082 2633 449 300
9...... Acid phosphate.............. 3720 3238 482 320
10...... Acid phosphate............. 3213 2895 318 310
11...... Acid phosphate ............. 3783 3356 427 390
12...... Acid phosphate............. 3357 3177 180 380
13...... Acid phosphate. ............. 3916 3177 739 630
14....... Acid phosphate. ............. 3659 3356 303 440
15...... Acid phosphate .............. 3396 2895 501 530
16 ...... Acid phosphate............. 4372 3469 903 600
17...... Acid phosphate .............. 4286 3794 492 290
18..... Acid phosphate ............. 3861 3554 307 280
19 ...... Acid phosphate.............. 3598 2959 639 450
20...... Acid phosphate.............. 3472 2839 633 310
21...... Acid phosphate.............. 3456 2839 617 410
22...... Acid phosphate .............. 3516 2959 557 630
23...... Acid phosphate ............ 4210 3554 656 370
24...... Dissolved bone black......... 4115 3794 321 430
25...... Steamedbone................ 3609 3098 511 230
26...... Steamed bone.............. 4524 3651 873 510
27...... Basic slag................... 3643 3033 610 340
28...... Basic slag.................. 3901 3236 665 630
29...... Acid phosphate............. 3559 3236 323 340
30...... Acid phosphate............. 3434 3037 397 400
31...... Acid phosphate ............. 4145 3651 494 440
32...... Dissolved bone black......... 3530 3098 432 450
33 ..... Floats ..................... 3197 2904 293 330
34 ..... Floats. ..... .............. 4095 3191 904 650
35 ..... Floats ..................... 4091 3035 1056 1010
36 ..... Floats ..................... 4466 2795 1671 1400
37...... Acid phosphate.............. 3270 2795 475 420
38...... Acid phosphate.............. 3877 3035 842 540
39...... Acid phosphate.............. 3507 3191 316 420
40...... Acid phosphate ............. 3529 2904 625 510
41...... Acid phosphate ............. 3432 2997 435 300
42...... Acid phosphate.............. 3510 2820 690 520
43 ...... No fertilizer................. 3348 3348 0 -30
44...... Acid phosphate.............. 3815 3142 673 380
45...... Acid phosphate.............. 3735 3142 593 490
46....... Acid phosphate.............. 3716 3348 368 320
47...... Acid phosphate............. 3192 2860 332 400
48...... Acid phosphate ............. 3529 2997 532 460
78 DEPARTMENT OF AGRICULTURE
Loss of Phosphoric Acid
No table is included to show the loss of phosphoric acid
since this loss has been extremely small. At the end of
four years it was found that only .05 of one per cent of the
amount applied was lost in the drainage water. This in-
dicates that the soil is able to absorb large amounts of
soluble phosphoric acid. That this is true is shown by
the fact that the soil used contained 50 per cent more phos-
phoric acid at the end of five years than it did at the begin-
ning of the experiment.
In studying the effect of the fertilizer used on the com-
position of the soil, especial attention was given to the
phosphoric acid. Work at the Experiment Station with
soil tanks has shown that the loss of phosphoric acid in the
drainage water where acid phosphate was used was so
small as to be negligible, and that practically all the phos-
phoric acid applied was retained by the soil. The work
with the grove soils confirmed these results. Samples of
soil from the fertilized plots and from the middle of the
tree rows were taken from time to time to a depth of 9
inches, and determinations made of the phosphoric acid.
Work elsewhere has shown that the greater part of the
phosphoric acid absorbed by soils is retained in the upper
plowed soil, so in this work sampling to a depth of 9 inches
was considered sufficient. The difference between the
amount of phosphoric acid in the soil of the plot and that
in the corresponding middle would show the quantity fixed
by the soil. These results for the different plots are given
in Table 6. In order to make the results easily comparable
they have been calculated to pounds per acre. The figures
in the table represent in every instance the average of the
results obtained from three different samplings of soil,
the third being taken in July, 1915. The second column
from the right shows the increase in phosphoric acid con-
tent, due to the absorption by the soil of the phosphate
fertilizer applied. It will be noted that these figures vary
considerably among themselves, even where the amount
and form of phosphoric acid applied has been identical.
This variation can be accounted for by the difficulty of
obtaining samples of soil which are perfectly representative
of the plots. However, it will be noted that those plots
receiving the largest applications of fertilizer also show the
greatest amounts of phosphoric acid retained. Plot 4,
SOILS AND FERTILIZERS 79
receiving four times the standard quantity of fertilizer,
shows the greatest fixation, an increase of 1713 pounds
per acre being noted. The source of the phosphoric acid
on this plot was acid phosphate. Plot 36, receiving the
same amount of actual phosphoric acid as plot 4, but in
the form of floats, shows a gain practically the same as
plot 4. Both these plots show an increase of over 50 per
cent. Although five different sources of phosphoric acid
were used on the plots, the form in which it was used does
not appear to have had any influence on the power of the
soil to absorb this material, the water-soluble form being
retained as thoroughly as the insoluble forms.
Changes of Phosphoric Acid in Soil
It is believed that the figures in the last column of Table
6 throw some light on the question as to what forms the
phosphoric acid assume after being incorporated with the
soil. It is generally agreed upon among soil investigators
that the phosphoric acid of the soil exists mainly in three
forms, namely, the phosphates of lime, iron, and alumina.
It is generally considered that the last two forms are much
less available to plants than the first form. Indeed it is
held by many that the phosphates of iron and alumina
are but slightly available because of their practical in-
solubility in the soil water. Phosphate of lime, on the
other hand, dissolves slowly in the soil water containing
carbonic acid gas and other weak acids and is thus con-
sidered more available to plants. The fixation of soluble
phosphoric acid in the soil is explained by the fact that it
combines with one or more of the compounds of iron,
aluminum or lime present and thus assumes an insoluble
form. It then becomes a matter of some practical impor-
tance to know whether the phosphoric acid added to the
soil assumes the form of the insoluble iron and aluminum
phosphates or the more readily available phosphate of
lime. A method of treatment which it is believed will
distinguish between the different forms has been developed
by soil chemists and has been used to some extent. It de-
pends upon digesting the soil in a weak solution of nitric
acid, which will dissolve the phosphate of lime present but
which has no effect upon the phosphate of iron and
alumina. A given weight of soil was treated with fifth-
normal nitric acid (about 1.26 per cent acid) and the
amount of phosphoric acid dissolved out determined, this
dissolved phosphoric acid being regarded as coming en-
tirely from the phosphate of lime present. The soil samples
80 DEPARTMENT OF AGRICULTURE
used were those on which the total phosphoric acid had
been determined as shown in the table. The results given
in the table represent the difference between the amounts
dissolved from the plot soils and those of the correspond-
ing middles, thus representing the increase in the acid
soluble phosphoric acid of the fertilized plots, and are
calculated to pounds per acre.
Some interesting facts are brought out by comparing
these results with the figures representing the increase in
total phosphoric acid. Those plots showing the greatest
increase in total phosphoric acid also show the greatest
increase in acid-soluble. Plot 4 again shows the greatest
increase, followed by plot 36. The average increase in
acid-soluble phosphoric acid for all the plots (omitting
plot 43) is 494 pounds, as compared with an average in-
crease in total of 586 pounds. Assuming that the acid
used dissolved out only phosphate of lime and no iron or
aluminum phosphate, these figures indicate that about
80 per cent of the increase in phosphoric acid content in
the plots has been fixed in the form of phosphate of lime.
Table 7 gives the amount of nitrogen in pounds per
acre to a depth of 9 inches. The soil samples taken from
the plots and from the middles at the end of the experi-
ment in 1918. One fact brought out here is the consider-
ably smaller amount of nitrogen in the clean culture plots,
46, 47 and 48, as compared with the remaining forty-five
plots. The average amount of nitrogen in these three
plots is 740 pounds per acre, as compared with an average
for the others of 1220 pounds an acre, indicating a loss
of 480 pounds or 39 per cent. This loss must be attributed
largely to the effects of the continuous cultivation. This
practice leads to more rapid nitrification of the organic
nitrogen of the soil, changing the insoluble nitrogen to the
soluble nitrogen form which is easily leached out. This loss
of organic matter also means a decrease in the capacity of
the soil for holding moisture and soluble fertilizers added
The average of the forty-eight soils taken from the
middles is 1030 pounds of nitrogen per acre. It is interest-
ing to compare this figure with the average of fifteen
samplings taken at the beginning of the experiment in 1909.
These samples were taken at various places over the field
and probably give a fair average of the nitrogen content
at that time. The amount of nitrogen found in this way
SOILS AND FERTILIZERS 81
was 1080 pounds per acre. This is so close to the average
for the middles (1030 pounds) at the end of the experi-
ment that it is reasonable to assume that the unfertilized
soil between the tree rows neither gained nor lost in nitrogen
during the ten years. In other words, the loss of nitrogen
through leaching was counterbalanced by the addition of
nitrogen by means of the leguminous cover crop. The
fertilized plots have gained slightly in nitrogen as com-
pared with the soils from the middle of the rows. Omit-
ting the clean culture plots and the no fertilizer plot, the
average is 1220 pounds per acre, a gain over the middles
of 190 pounds.
TABLE 7.-NITROGEN CONTENT OF
in Plot in Middle
Potash in Grove Soil
The amount of potash present in the different plots at
the end of the experiment in 1918 is given in Table 8.
The results are calculated in pounds per acre to a depth of
9 inches, and represent the total amount of potash in
the soil at that depth. The unfertilized middles were also
82 DEPARTMENT OF AGRICULTURE
sampled, and potash determined in seven of these soils.
The average of these seven soils amounts to 1140 pounds
per acre. By comparing this figure with those for the
various plots, the increase in the latter due to the potash
in the fertilizer may be determined. It will be noted that
all the fertilized plots show an increase over the unfertilized
soil, thus indicating that this soil was able to retain at
least a portion of the soluble potash applied. The average
increase for the forty-seven plots amounts to 660 pounds
per acre, or an increase of over 50 per cent for the ten
years of the experiment.
A large portion of the potash in the plot soils is held in
a very insoluble form, probably largely as feldspar. Treat-
ment of these soils with strong hydrochloric acid dissolved
on the average only 15 per cent of the total potash present.
TABLE 8.-POTASH CONTENT OF PLOT SOILS AT END OF
EXPERIMENT IN 1918
Plot Potash Plot Potash
1 ................ 1620 25 ................ 2160
2 ................ 1800 26 ................ 1530
3 ................ 2010 27 ................ 2070
4 ................ 2040 28 ................ 1950
5 ................ 1740 29 ................ 1620
6 ................ 1830 30 ................ 2040
7 ................ 1740 31 ................ 1950
8 ................ 1740 32 ................ 2040
9 ................ 1830 33 ................ 1440
10 ................ 1530 34 ................ 1950
11 ................ 1740 35 ................ 1530
12 ................ 1950 36 ................ 1830
13 ................ 1830 37 ................ 1830
14 ................ 1950 38 ................ 2160
15 ................ 1620 39 ................ 1440
16 ................ 1740 40 ................ 1680
17 ................ 1530 41 ................ 1950
18 ................ 1740 42 ............... 1830
19 ................ 2160 43 ................ 1140
20 ................ 1950 44 ................ 1830
21 ................ 2250 45 ......... ...... 1620
22 ................ 1950 46 ................ 1620
23 ................ 1440 47 ................ 1440
24 ........ 2040 48 ................ 1530
Unfertilized soil 1140.
SOILS AND FERTILIZERS
Use in New Territory
The use of superphosphate and of fertilizers of high
phosphoric acid content has increased very rapidly in new
fertilizer territory during the past 10 to 15 years. The
increases have been very pronounced in Illinois, Wisconsin,
Iowa, Minnesota, Mississippi, Louisiana, Arkansas, Ken-
tucky, Tennessee, Texas, California, Washington and Ore-
gon. The tonnage sold in these States in 1920 and in 1930
was as follows:
W isconsin ...................................
Minnesota .............................. .....
Kentucky .................. ..................
Mississippi ........................... .......
Louisiana ................. ...................
Washington ............. ...................
Oregon .............. ...................
Total, 18 States ........................... 677,219
There were very significant increases in many other
States which are even more noteworthy when it is re-
membered that 1920 was the peak year of consumption up
to that date and was not exceeded until 1925. The increase
of 117 per cent in the 13 States named above takes no
account of the increased plant food content in 1930 as
compared to 1920. Such an increase certainly speaks well
for the educational work among farmers that has been
carried on by extension agencies and by the fertilizer
Within the past five years a good beginning in the
use of fertilizer has been made in Montana, Wyoming,
Idaho, Colorado, Utah, Arizona and New Mexico. In 1920
these States used less than 100 tons of fertilizer and in
1925 only 2,950 tons. But in the depression year of 1931
their combined consumption was 14,920 tons. Further-
more a large portion of this tonnage consisted of triple
superphosphate and the average plant food content was
probably nearly double that of the average fertilizer sold
in the Eastern States. As a result of experiments carried
84 DEPARTMENT OF AGRICULTURE
on by the U. S. Department of Agriculture and the beet
sugar companies, the use of superphosphate on sugar beets
is rapidly becoming standard practice.
Effect of Fertilizers on Growth
The effect of the various fertilizer treatments used in
producing growth was measured each year by taking the
diameter of the tree trunks. Table 9 gives the average
measurements of the trees in the various plots at the end
of the experiment. The measurements are given in thirty-
seconds of an inch. These figures were obtained by sub-
tracting the original diameter of the tree when set out from
the final measurement at the end of 1918. In each case
they are the average of the ten trees in each plot, and give
the actual increase made by the trees. Similar measure-
ments were taken every year during the continuation of
the experiment. The standing of the different plots from
year to year, beginning with 1910 is shown in Table 10.
In Table 9 the plots are arranged in the order of the
increase in growth made at the end of the ten years, the
plot making the largest increase being placed at the head
of the list. This table brings out the fact that in this
experiment a number of sources of materials have proven
almost equally valuable in producing growth and that sev-
eral have had an injurious effect. Among the fertilizers
used on the plots making the most growth no single source
has any remarkable superiority over others used, although
there is considerable variation in the effect of the differ-
ent materials. The results of this work emphasize the fact
that the citrus grower need not be restricted in his choice
of fertilizers to one particular material, but that there are
a number of sources of the three essential elements which
can be used to advantage. It should be stated that the soil
on which this experiment was located was somewhat above
the average in fertility, especially in phosphoric acid con-
tent. This fact has served to minimize differences which
might otherwise have developed between the fertilizers
used and especially the sources of phosphoric acid. The
behavior of plot 43, which received no fertilizer during
the time the experiment continued brings out the fact
that the soil was unusually well supplied with plant food.
However, a study of the table brings out the fact that the
plots making the best growth have received the standard
mixture of sulphate of ammonia, acid phosphate and high
grade sulphate of potash. Of the best 16 plots, all but one
SOILS AND FERTILIZERS 85
TABLE 9.-GAIN IN DIAMETER OF TREES FOR 10 YEARS
Plot Gain Fertilizer Treatment
1 138 One-half standard.
1 183 One-half standard.
12 136 Standard and air-slaked lime.
13 134 Standard. Mulched.
47 183 Nitrogen from dried blood. Clean culture.
46 132 Standard. Clean culture.
16 130 Nitrogen, % nitrate of soda, % sulphate of ammonia.
45 130 Standard. Mulched.
31 128 Standard.
48 127 Nitrogen from nitrate of soda. Clean culture.
37 127 Potash from low-grade sulphate.
25 127 Phosphoric acid from steamed bone.
22 126 Nitrogen, '% cottonseed meal, % sulphate of ammonia.
8 125 Phosphoric acid and potash decreased by one-half.
30 124 Acid phosphate, nitrate of soda, hardwood ashes.
41 124 Standard.
6 123 Phosphoric acid and potash increased by one-half.
36 123 Phosphoric acid from floats. (4 times amt.) Cotton-
35 122 Phosphoric acid from floats. (4 times amt.)
9 121 Phosphoric acid and nitrogen decreased by one-half.
38 120 Potash from muriate.
44 118 Standard.
21 114 Nitrogen from cottonseed meal. Ground limestone.
23 114 Nitrogen, % cottonseed meal, % nitrate of soda.
3 114 Twice standard.
20 113 Nitrogen from cottonseed meal.
26 112 Phosphoric acid from steamed bone. (2 times amt.)
32 112 Phosphoric acid from dissolved bone black.
34 111 Phosphoric acid from floats. (2 times amt.)
42 111 Potash from nitrate of potash. Balance nitrogen, ni-
trate of soda.
19 110 Nitrogen, % nitrate of soda, % dried blood.
11 110 Standard and ground limestone.
24 110 Phosphoric acid from dissolved bone black.
15 109 Nitrogen from nitrate of soda.
27 109 Phosphoric acid from Thomas slag. Nitrate of soda.
7 108 Nitrogen and potash increased by one-half.
33 107 Phosphoric acid from floats.
18 106 Nitrogen, % sulphate of ammonia, % dried blood.
29 105 7% per cent potash in June, 7% in October, 3 in February.
40 104 Potash from kainit.
14 103 1 Standard.
10 102 Nitrogen and potash decreased by one-half.
43 101 No fertilizer.
28 96 Phosphoric acid from Thomas slag. (2 times amt.) Ni-
trate of soda.
17 90 Nitrogen from dried blood.
39 88 Standard. Ground limestone.
5 75 Phosphoric acid and nitrogen increased by one-half.
4 65 Four times standard.
86 DEPARTMENT OF AGRICULTURE
have received acid phosphate as the source of phosphoric
acid. The one exception is plot number 25, receiving
steamed bone and ranking twelfth in the list. All but
two plots in these sixteen have received high grade sul-
phate of potash as the source of potash. The two excep-
tions are plot number 37 receiving low grade sulphate of
potash and plot number 30 receiving hardwood ashes and
the best 10 plots. Sulphate of ammonia, nitrate of soda,
ranking eleventh and fifteenth, respectively. Of the five
different sources of nitrogen used, all are represented in
the best 10 plots. Sulphate of ammonia, nitrate of soda,
and the nitrogen of steamed bone have all produced good
growth. It will be noted that plot number 2, receiving the
standard mixture, stands at the head of the list. As stated
elsewhere, this standard mixture consisted of sulphate of
ammonia, acid phosphate, and high grade sulphate of
potash. This mixture was applied at the rate of 2 pounds
per tree three times per year. The amount was increased
as the trees increased in size, the application finally being
at the rate of 6 pounds three times per year.
Plot number 1, receiving one-half the standard amount,
or at the beginning 1 pound per tree three times per year,
shows practically the same increase in growth as plot 2.
Plot number 3, receiving twice the standard amount, or
4 pounds per tree at the beginning, ranks twenty-fifth,
while plot number 4, receiving four times the standard
amount or 8 pounds per tree ranks at the foot, having made
less growth than any of the plots. The standing of this
series of four plots brings out the fact that in this experi-
ment plot 1 was receiving about the optimum amount of
fertilizer which it would pay to apply to trees of this age,
and that plot number 2 received the maximum amount
which could be applied without inducing injury. The fact
that plots 2 and 1 made practically the same amount of
growth indicates that the former was receiving more ferti-
lizer than the trees could profitably use, although not enough
to injure them in any way. The appearance of these two
plots was very similar, the eye not being able to detect
any difference in size, character of growth, or appearances
of the leaves. Plot number 3, receiving twice the standard
amount of fertilizer, has developed considerable injury.
This injury was shown soon after the beginning of the
experiment, was quite severe for several years, but finally
became much less apparent. This would indicate that 4
pounds per tree three times per year was about the maxi-
mum amount of fertilizer which could be applied to young
SOILS AND FERTILIZERS 87
TABLE 10.-RANK OF PLOTS
Rank 1910 1911 1912 1913 1914 1915 1916 1917 1918
1 46 46 46 47 2 2 2 2 2
2 30 47 47 46 1 47 1 1 1
3 47 35 35 36 47 1 46 47 12
4 41 41 41 37 46 13 13 48 13
5 29 44 48 13 13 12 12 12 47
6 24 36 2 41 36 48 47 13 46
7 26 48 36 48 41 36 48 25 16
8 5 37 37 12 12 37 45 46 45
9 13 43 22 22 37 46 25 8 31
10 35 16 44 2 45 22 37 31 48
11 31 22 30 35 48 30 22 37 37
12 22 2 43 30 22 41 36 9 25
13 23 8 42 31 30 25 30 36 22
14 43 42 12 45 44 35 31 11 8
15 47 6 13 38 21 31 41 35 30
16 19 30 1 44 38 21 8 6 41
17 36 45 38 34 43 44 35 22 6
18 42 26 20 8 35 38 11 30 36
19 17 25 31 26 8 45 9 44 35
20 30 38 8 43 9 11 6 45 9
21 21 12 16 21 29 6 16 16 38
22 49 11 34 29 31 43 21 20 44
23 37 19 26 25 23 9 26 24 21
24 14 34 6 23 16 29 29 23 23
25 15 31 29 42 32 23 38 32 3
26 8 33 33 20 42 8 32 29 20
27 27 39 23 32 25 16 23 26 26
28 44 20 11 6 24 32 44 21 32
29 32 24 32 28 20 34 20 38 34
30 34 29 19 1 11 26 24 42 42
31 6 1 45 33 6 24 3 3 19
32 38 7 25 9 39 15 34 19 11
33 35 13 7 11 34 20 19 15 24
34 4 27 21 39 33 42 43 10 15
35 3 9 39 24 26 28 28 14 27
36 25 32 9 19 15 10 42 34 7
37 16 14 24 7 7 3 15 27 33
38 10 23 14 3 3 33 27 33 18
39 18 21 27 10 19 39 33 43 29
40 40 3 3 15 10 19 7 18 40
41 11 5 28 18 14 27 10 7 14
42 21 28 10 14 40 7 14 40 10
43 9 17 40 27 17 14 18 41 43
44 12 10 15 40 27 40 40 28 28
45 28 40 17 10 18 18 39 17 17
46 2 15 5 5 28 5 17 39 39
47 1 18 18 17 5 17 5 5 5
48 7 4 4 4 4 4 4 4 4
88 DEPARTMENT OF AGRICULTURE
trees and not kill them outright. The injury was severe
during the first few years but the trees managed to survive
and finally to overcome the injurious effects. The behavior
of this plot in thus overcoming the injurious effects of too
much fertilizer is shown in Table 10. It will be noted that
in 1911 and 1912 this plot ranked number forty in the list.
In 1913 and 1914 it rose to thirty-eighth; in 1915 to thirty-
seventh; in 1916 and 1917 to thirty-first; and in 1918 to
twenty-fifth. This rise in rank indicates that as the trees
became older they were better able to withstand the effects
produced by too much fertilizer. The early injury, however,
resulted in a permanent stunting of the trees. At the end of
the experiment they were about three-fourths as large as
the trees of plots 1 and 2.
Plot 4 shows the maximum injury from the use of too
much fertilizer. These trees were stunted from the begin-
ning and have made very little growth. By the winter
of 1912 half of the trees in this plot were dead and had to
be replaced by others. In the spring of 1913 the excessive
applications were discontinued and from that time on only
one pound per tree was used three times per year. The
new trees used to replace those killed by the fertilizer have
failed to make much growth. At the end of the experiment
this plot was less than one-fourth the size of plots 1 and 2
and consisted of almost worthless trees which will probably
never amount to much.
The behavior of plots numbers 5, 6 and 7 is interesting
in this connection, because of its bearing on the question as
to which of the fertilizing elements used was chiefly re-
sponsible for the injury produced. In this series of three
plots two of the elements were increased by one-half, the
third being used in the standard amount. In the mixture
applied to plot 6 the acid phosphate and high grade sul-
phate potash used was one and one-half times the amount
used in the standard mixture, the sulphate of ammonia
remaining the same as in the latter. Plot 7 received 1%
times the nitrogen and potash of the standard and plot
5 received 11/2 times the nitrogen and phosphoric acid of
the standard. It will be noted that the least amount of
growth was made by plot 5 which ranks forty-seventh in
the list. This plot showed all the signs of severe injury
caused by too much fertilizer. In the table showing the
rank of the plots by years plot 5 stood forty-first in 1911
and dropped still lower from year to year, until for the last
three years it stood next to the lowest.
SOILS AND FERTILIZERS 89
Plot 7, where the nitrogen and potash were increased,
has made a better growth than plot 5 but not as much
as plot 6. The latter shows no injury from the increased
phosphoric acid and potash used. The trees in plot 7
show some injury caused by too much fertilizer but the
injury is not quite so marked as in plot 5. The behavior
of these three plots brings out the fact that excessive
quantities of nitrogen are much more injurious than simi-
lar quantities of phosphoric acid and potash and that in-
creased ratios of nitrogen and potash are less injurious
than similar increases of nitrogen and phosphoric acid.
The mulched plots and the plots which received clean
cultivation the entire year are among the best in the grove.
This treatment has been of benefit in two ways: by con-
serving moisture and supplying additional nitrogen. The
cultivation through the year has led to increased nitrifica-
tion of the organic matter of the soil thus liberating a sup-
ply of available nitrogen in addition to that supplied in the
fertilizer. Determinations on several occasions during the
early years of the experiment have shown that these plots
contained more nitrates in the soil than was found in the
soil of adjacent plots. The soil on which the plots were
located was naturally a rather dry soil so that the continu-
ous cultivation and the mulch of dry leaves and weeds have
aided in conserving moisture during dry periods. Table
10 shows that the clean culture plots made more growth
than any others during the early years of the experiment
but that after 1913 they did not do quite so well. This
would indicate that for young trees continuous clean culti-
vation is of benefit in promoting good vigorous growth,
but after a few years it is possible to cultivate too much.
Determinations made at the end of the experiment show
that the soil of the clean culture plots has lost about 18
per cent of the organic matter due to the continuous culti-
vation as compared with the soil of adjacent plots.
90 DEPARTMENT OF AGRICULTURE
PRACTICABILITY OF FERTILIZATION OF CITRUS
From "Citrus Leaves", California
FERTILIZER experiments planned and executed by
various members of the Citrus Experiment Station
staff and several individual growers on four differ-
ent citrus growing centers through five separate field trials
over a period of some fifteen years have enabled R. S. Vaile,
of the station, to give growers eleven definite recommenda-
tions resulting from the work.
Location of Experiments
The five field trials were conducted at Rubidoux, near
Riverside, begun in 1907; Arlington, begun in 1915 and
closed February, 1920; Ontario, begun in 1915 and closed
in February, 1921; Chula Vista, begun in 1915 and closed
December, 1920, and at Naranjo, where the trials begun
in March, 1915, and continued until December of 1920.
Several Conclusions Reached
The basic conclusion resulting from this extended work,
is that citrus groves in Southern California must be ferti-
lized if they are to be profitable. "But little definite in-
formation was obtained concerning either the specific kinds
and amounts of fertilizer or the time and method of ap-
plication, from which the greatest returns may be ex-
pected," states Mr. R. S. Vaile in his report. "Certain
points of emphasis are consistently shown by each of these
experiments," he advises, and points out the following con-
1. There is a positive value to be derived from ferti-
lizing citrus trees on any of the soils involved in these
trials, as measured by increased crop yield.
2. This value seems to be associated primarily with the
use of nitrogen.
3. No definite value can be attached to the use of potash
or phosphoric acid in any of the trials reported, either
when used in conjunction with nitrogen or when used alone.
SOILS AND FERTILIZERS 91
4. Lime, when applied as ground limestone, has not been
of value in the trials reported except at Chula Vista on the
Kimball sandy loam soil.
5. Bulky organic material has been of large importance
in citrus fertilization.
6. Specific fertilizing materials have given different
results in different locations, so much so that findings
from one set of field trials should not be too liberally in-
terpreted for any other set of conditions.
7. Trials with fruit trees are generally designed to
measure the effect of contrasting systems of orchard man-
agement and can not furnish exact answers to specific
questions concerning the economy of any certain kind,
amount, or method of application of fertilizer.
8. The field trials and orchard surveys reported upon
indicate clearly that fertilization is required for the eco-
nomical production of citrus fruits under usual Southern
California conditions. That the application of fertilizer is
often delayed too long after the planting of an orchard
and that larger applications might be used with profit, are
points that are also indicated.
9. Groves that have been allowed to deteriorate through
lack of fertilizer may be greatly improved by the use of
nitrogenous fertilizer materials. Where deterioration is
manifested by typical mottle leaf and attendant character-
istics, it appears that a correction of this particular trouble
is not found in the use of commercial fertilizers, particularly
10. Covering the ground with a straw mulch, thus
eliminating the necessity for any tillage operations, may
be expected greatly to improve rundown citrus groves. This
method of culture is likely to be limited in effectiveness to
a period of two or three years, following which ordinary
tillage should again be resorted to. This system of man-
agement is not well adapted to clay loam soils.
11. The use of winter green-manure crops has been
followed by conflicting results, in different trials. In one
case a marked increase in yield and an improvement in tree
condition resulted; in a second case there was a slight de-
crease in yield; in a third case the results seemed to be
negative. The failure of the cover crop to always produce
92 DEPARTMENT OF AGRICULTURE
increased yields can be apparently accounted for in some
cases, but has not been in other cases.
So far as the average grower of citrus fruits is con-
cerned, the most valuable deductions resulting from this
long and tedious experimentation are the unqualified con-
clusions that fertilization is required for economical pro-
duction; that the value of both potash and phosphoric acid
have been apparently greatly overestimated of late by
some growers; that nitrogenous fertilizers will greatly aid
in the rejuvenation of rundown groves; that straw mulches,
by eliminating the necessity of tillage operation also assist
in this rejuvenation and that the use of winter green-
manure crops is not yet proven to be a definite factor in
fertilization, either positively or negatively.
In April, 1907, field trials were laid out at Rubidoux to
test the effect of various fertilizers on oranges and lemons.
Twenty major plots were used, each containing 6 Wash-
ington Naval orange trees, 6 Valencia orange trees, 6
Eureka lemon trees, 6 Valencia orange trees, all budded
on sweet orange root stocks, and planted 20 feet apart in
squares, giving 108 trees per acre.
Table one shows the plot arrangement and fertilizers
used. The applications in detail were:
Plot A, nitrate of soda, blood, bone and sulfate of potash
(known as complete commercial fertilizer); plot B, no
fertilizer; plot C, dried blood; plot D, sulfate of potash;
plot E, steamed bone; plot F, stable manure; plot G, nitrate
of soda, blood and bone; plot H, nitrate of soda; plot I,
muriate of potash (sulfate of potash 1920-1921); plot J,
superphosphate; plot K, steamed bone and sulfate of potash;
plot L, nitrate of soda, blood, and sulfate of potash; plot
M, no fertilizer; plot N, superphosphate and blood to equal
nitrogen in bone plots (blood was added in 1914); plot O,
stable manure and rock phosphate; plot P, steamed bone;
plot Q, nitrate of soda, blood, superphosphate and sulfate
of potash; plot R, sulfate of potash; plot S, dried blood;
plot T, unfertilized. Plot U and V contain trees on sweet
orange stock, Eureka lemons, Valencia and naval oranges,
and were treated with manure covercrops.
SOILS AND FERTILIZERS 93
TABLE 1.-RUBIDOUX TRIALS
Total Yield in Pounds Per Tree, Averaged for Each Plot. Nine Seasons
With Oranges, 1912-1920, Inclusive. Six Seasons With
Lemons, 1915-1920, Inclusive.*
O N M L K Plot
378 153 90 406 252 Navel
756 378 225 486 576 Valencia
503 305 186 268 341 Eureka
800 350 180 487 366 Lisbon
V T S R Q P Plot
423 108 522 99 603 198 Navel
648 261 756 252 630 468 Valencia
630 99 500 173 530 409 Eureka
.. 39 608 92 714 535 Lisbon
*In December, 1911, and January, 1913, the lemon yields were seri-
ously affected by frost, so that no data are submitted prior to the
94 DEPARTMENT OF AGRICULTURE
TABLE 2.-RUBIDOUX TRIALS
Yields by Plots in Pounds Per Tree. (1). Average for Year by Three-
1912-1914 1915-1917 1918-120
Plot Age5, 67 Ae8 9, 10 Age 11 12. 13
Navel Val. Navel Val. Navel Val.
A 36 53 67 75 39 17
B 11 9 0 3 0 1
C 34 72 63 104 24 49
D 13 12 0 17 0 1
E 41 47 31 65 0 17
F 31 53 65 128 27 98
G 29 55 70 71 30 12
H 40 59 34 17 9 1
I 11 27 0 23 0 2
J 13 33 12 49 0 10
K 31 45 45 116 2 30
L 29 57 77 77 27 26
M 20 33 10 38 0 2
N 28 36 21 66 1 24
0 28 57 73 124 24 72
P 22 44 44 91 1 16
Q 34 52 122 130 44 24
R 24 40 9 38 0 6
S 49 56 108 135 17 62
T 27 40 9 42 0 6
U 58 95 173 146 63 138
V 36 47 75 83 30 88
(1)-Lemon yields are not included in
injury during the first three-year period.
this table because of frost
The trees were first fertilized in 1907, when small ap-
plications were made. The amounts were increased until
in 1914 when the following annual applications were de-
1.34 pounds actual nitrogen per tree
2.70 pounds actual phosphoric acid per tree
1.35 pounds actual potash per tree
which means approximately 25 pounds per tree of 5-10-5
formula fertilizer on the complete fertilizer plots A and Q.
10 pounds per tree of dried blood on C and S
9 pounds per tree of nitrate of soda on H
14 pounds per tree of steamed bone on E, K, P
2% pounds per tree of sulphate of potash on D, I, R
13 pounds per tree of superphosphate on J
10 cubic feet per tree of manure on F and 0
8 cubic feet of manure per tree on U and V.
SOILS AND FERTILIZERS 95
Accompanying Tables No. 1 and No. 2 clearly indicate
the exact yield returns in pounds and percentage of good
TABLE 3.-RUBIDOUX TRIALS
Summary of Yields by Groups of Plots
Average Annual Yield Per Tree in Three-Year Periods
1191914 1915-1917 1918-1920
Navel Val. Navel Val. Navel Val.
U, V...... 27 71 124 115 46 113 Cover crop and manure.
F, O0...... 20 55 69 126 26 85 Manure.
C, S...... 42 64 86 120 20 56 Dried blood.
H....... 40 59 34 17 9 1 Nitrate of soda.
A, Q..... 35 52 94 102 42 20 Complete.
G, L...... 29 56 74 74 28 19 Two elements with
E.K, P... 31 45 40 91 1 21 Steamed bone.
D, I, R... 16 26 3 26 0 3 Potash.
J......... 13 33 12 49 0 10 Superphosphate.
B, M, T... 19 27 6 28 0 3 Unfertilized.
Eureka Lisbon Eureka Lisbon Eureka Lisbon
U, V....... .. .. ..... 184 ... 124
F. 0............ .. 139 115 33 115
C, S.......... ... .. 126 99 23 68
H ............ ... ... 40 56 0 1
A,Q ........... ... .. 134 128 9 26
G, L.................. 85 98 4 26
E, K, P......... .. ... 89 90 3 31
D,I, .............. 40 33 3 2
J........ ...... .. 99 34 7 2
B,M, T........ .. 37 25 2 2
Other data besides yields may be of value in comparing
the effects of different treatments. The accompanying
Table No. 4 gives a comparison of fruit quality for the year
1914 and for the navel crop of 1921.
Space will not permit of an exhaustive survey of the
other trials. The above tables and charts give a graphic
insight into the methods employed and the general results
obtained from the Rubidoux experiment. The general con-
96 DEPARTMENT OF AGRICULTURE
clusions drawn at the beginning of this article are based
on all experiments, and represent the sum total of all
deductions made. Fertilization investigation is a long,
comparatively expensive and not highly satisfactory en-
The net results to the grower of the years and money
expended in carrying out these experiments cannot be
measured by any existing standards. The average grower
is not in a position to carry on such extensive work and he
naturally must rely upon state and federal organizations
to protect his interests. Thousands of dollars have been
invested in either worthless or over-valued fertilizers dur-
ing the last few years, and the grower must have some
authentic source of information for his guidance. Many
become dissatisfied with the apparently slow progress made
by official state representatives, but it must be borne
in mind that such experiments as these in question neces-
sarily require many months of careful study and applica-
tion, and those responsible for the work deserve great
TABLE 4.-RUBIDOUX TRIALS
Grade and Size of Fruit
GROUPS OF PLOTS
1914 1921 1914 1921
% Fancy f Choice % Best Sies
u,v ....................... 69 80 48 64
F, ...................... 76 76 36 62
C, S........................ 73 78 40 84
H.......................... 73 26 36 26
A.Q........................ 74 66 44 22
G.L................. ....... 78 47 39 39
D, I. R..................... 74 -* 36
J.......................... 72 -* 43 -
B, M, T.................... 71 -* 33 -*
*Not sufficient fruit to grade or size.
SOILS AND FERTILIZERS 97
THE FERTILIZATION OF COTTON
Queensland Cotton Journal
ONE of the boy competitors, J. Spoor, Mundubbera,
raises the above important question, and at this stage
we feel that we cannot do better than quote from
the "Georgia Experiment Station Bulletin," which gave
the results of four years nitrogen test, using cottonseed
meal, nitrate of soda, and sulphate of ammonia as sources
It will be noticed that while the yields for the four
years are low, sulphate of ammonia made the best average
for three years. The tables for the fourth year show the
yield from the use of cottonseed meal and sulphate of
ammonia to be the same. I believe this can be accounted
for by the inequality of the soil. One of the cottonseed
meal plots was more fertile than any other plot.
The nitrate of soda and sulphate of ammonia formulas
were made to carry precisely the same number of pounds
of phosphoric acid, potash and nitrogen as was in the cotton
Each formula was drilled in a deep furrow and bedded
on before planting. Each plot was the same size, consist-
ing of an equal number of rows, and repeated until all
the rows were fertilized. Each year there was left as a
check, four rows in each acre not fertilized. Calculating
the cost of the nitrogen of each formula at the market
price, it is ascertained that nitrogen in cottonseed meal
costs 20 cents per pound, nitrate of soda 158/4 cents per
pound, and sulphate of ammonia 15 cents per pound. It
will be seen from this experiment running through four
years, while nitrogen from sulphate of ammonia costs less
than the nitrogen in cottonseed meal and nitrate of soda,
it made the most and the cheapest cotton.
Pounds Cottonseed Per Acre
Average for 1909 1910 1911 1912 years
Cottonmeal plot ......... 1390 1246 1334 1277 1309
Nitrate of Soda ......... 1427 1269 1357 1257 1327
Sulfate of Ammonia ..... 1502 1297 1416 1277 1372
Check plot not fertilized.. 889 963 940
98 DEPARTMENT OF AGRICULTURE
Judging from the results I am warranted in recommend-
ing sulphate of ammonia as a better source of nitrogen for
cotton than either cottonseed meal or nitrate of soda. I
am also led to say that the cotton farmers could save a large
amount of hard earned money if they would exchange their
seed for meals and hulls and feed the meal and hulls to
cattle and apply, the resulting manure to their land, and
buy sulphate of ammonia to supply the necessary nitrogen.
Mr. J. C. Brunnich, F.I.C., in his booklet, "Complete Fer-
tilizer for Farm and Orchard," supplies some valuable
formula which might be more adapted to Queensland con-
ditions than the foregoing. He says:
Cotton does best on deep, sandy loams, or even on fairly
heavy clay, if it contains plenty of lime and a fair amount
of humus. When grown in rotation with other crops, more
particularly leguminous crops, only light dressing with
artificial fertilizers is required.
Apply per acre:-2 cwt. of superphosphate or basic
superphosphate or bonemeal; 1/2 cwt. of sulphate of potash;
1 to 11/ cwt. of dried blood or nitrate of soda.
Or-2 cwt. Thomas' phosphate or basic superphosphate
or rock phosphate; /2 cwt. sulphate of potash; Y1 cwt.
Or-3 to 4 cwt. of meatworks manure (with blood). %
cwt. sulphate of potash.
Or-From 3 to 6 cwt. of mixed fertilizer containing 8 to
10 per cent phosphoric acid, 22 to 3 per cent of nitrogen,
and 4 per cent of potash.
In localities where the crop is susceptible to blight the
following mixture should be tried:-2 cwt. Thomas' phos-
phate or basic superphosphate or rock phosphate; 1 to 1
cwt. kainit; 1 to 11/ cwt. of nitrate of soda or dried blood
E. B. Ferris, Director of the South Mississippi Experi-
ment Station at Poplarville, Mississippi, announces that
while unfertilized plots during the past year averaged 1,239
pounds of seed cotton per acre, 500 pounds of fertilizer
SOILS AND FERTILIZERS
per acre produced 1,800 pounds; 1,000 pounds of fertilizer
per acre produced 1,850; 1,500 pounds, 2,030, and 2,000
pounds, 2,050 pounds of seed cotton per acre. Valuing
the cotton at 8 cents per pound of seed cotton, and acid
phosphate at $18.00 per ton, nitrate of soda at $60.00 per
ton, and potash at $50.00, the net increase from these sev-
eral applications of fertilizers by plots, beginning with
that on which 500 pounds was used, was $32.88; 1,000
pounds per acre was $28.32; 1,500 pounds per acre, $34.16;
2,000 pounds, $27.20. The fertilizer applied analyzed 8-4-4.
In the case of similar tests with corn, using the same
fertilizer exactly, the plot on which no fertilizer was used
produced a yield of 1,238 pounds of slip-shucked ears per
acre; on the fertilized plots 500 pounds produced 3,010
pounds of corn; 1,500 pounds, 3,670; and 2,000 pounds,
3,710 pounds of corn per acre. Valuing the corn at 11/2
cents per pound for slip-shucked ears, which is a little bet-
ter than a dollar a bushel, the only plot showing a net in-
crease over the unfertilized plot was where 500 pounds of
fertilizer was used. The application of the larger amounts
showed a loss ranging from $1.67 to $13.81.
SOUTHERN EXPERIMENT STATIONS FIND POTASH
MORE IMPORTANT ON COTTON
More Potash Pays Big Profits in South Carolina
" CINCE there has been an unusual amount of cotton rust
due to a deficiency of available potash in recent years,
there has been a marked increase in the amount of
potash included in the average cotton fertilizer sold in the
state," according to the 48th annual report of the South
,Carolina Experiment Station. "Where there is a marked
deficiency of available potash in the soil, the cotton plants
shed their leaves early in the season which results in a large
portion of the cotton bolls not developing properly. These
undeveloped bolls do not open normally and the cotton is
often of poor quality and very difficult to pick."
In order to determine how much potash the fertilizer
should contain to produce best results field tests were con-
ducted on a number of Piedmont and Coastal Plain soils. The
basic fertilizer application was 600 pounds per acre of 5-10-0
and a side-dressing with 15 pounds of nitrogen. The aver-
age results of 4 years' work are as follows:*
*In pounds of seed cotton per acre.
100 DEPARTMENT OF AGRICULTURE
Average Incrm crers aser % Incrse.
Fertilizer Yield for Over Pr- Over No Over No
Analysis Each Rate ceding Rate Potash Potash
5-10-0 557 ... *.* ..
5-10-2% 874 317 317 56.9
5-10-5 1015 141 458 82.2
5-10-7% 1137 122 580 104.1
5-10-10 1243 106 686 123.2
5-10-12% 1288 45 731 131.2
It will be observed that the average yield of cotton in-
creased as the potash content of the fertilizer increased. In
commenting on the results of this work, the report observes
that "on the basis of these tests an investment ranging
from around 60 cents to $3.00 per acre in potash fertilizer
produced 106 to 241 pounds of lint cotton. At 10 cents per
pound for cotton this would be approximately $10.60 to
$24.10 per acre increase in value of lint cotton."
In a Service Sheet No. 177 issued by the Mississippi Delta
Station the results of the fertilizer elimination test in the
foothills area for 1935 are given. They are as follows, in
pounds of seed cotton per acre:
Nitrogen alone ................. 725.4 lbs.
Nitrogen and Phosphorus....... 842.4 "
Nitrogen and Potash ........... 994.5 "
Nit., Phos., and Potash......... 1111.5 "
Nitrogen alone ................ 729.9
Louisiana Station Names Fertilizers Adapted to Cotton
The best fertilizer for cotton on the more sandy types of
soil in the Coastal Plain area of Louisiana and areas sus-
ceptible to rust is 400 to 600 pounds per acre of a 6-10-7 or
4-8-6 mixture, according to Extension Circular 167 of the
Louisiana Experiment Station entitled "Fertilizers for Field
Crops in Louisiana." The same analyses at 600 pounds per
acre are recommended also for some areas in the Mississippi
bluff and terrace soils.
For other principal soil types of Louisiana the 4-8-4, 4-12-4
and 6-8-4 analyses are recommended in amounts 400 to 600
pounds per acre.
North Carolina Finds Potash Controls Rust
"Studies for the correction of soil conditions causing black
rust of cotton on Cecil Sandy Loam conducted in Iredell
County during one year indicate that the use of a high per-
centage of potash in a complete mixture reduces the preva-