Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED SOIL NUTRIENT COIVIPOSITIONS
AND METHODS OF USING SAME
BACKGROUND OF THE INVENTION
Field of the Invention.
The pfesent invention is broadly concerned with compositions and methods for
lowering the pH of soil microenvironments so as to increase the micronutrient
uptake
of growing plants. The compositions of the invention are preferably granulated
and
comprise ammonium sulfate, elemental sulfur, and a micronutrient selected from
the
group consisting of zinc, iron, manganese, copper, boron, cobalt, vanadium,
selenium,
silicon, nickel, and mixtures thereof. In the preferred methods of the
invention,
granulated compositions are applied to the soil resulting in the formation of
acidic soil
micro-environments, while the soil surrounding the microenvironments retains
its
original pH. Such localized low pH conditions lead to an increased
availability and
plant uptake of the important micronutrients. In an alternative embodiment,
non-
granulated compositions can be utilixed when it is desirable to decrease the
overall pH
of bulk soil.
Description of the Prior Art.
In order to maintain healthy growth, plants must extract a variety of elements
from the soil in which they grow. These elements include the so-called
micronutrients
zinc, iron, manganese, copper, boron, cobalt, vanadium, selenium, silicon, and
nickel.
However, many soils lack sufficient quantities ofthese micronutrients or
contain them
only in forms which can not be readily taken up by plants. To counteract these
deficiencies, sources of the deficient element(s) are commonly applied to
soils in order
to improve growth rates and yields obtained from crop plants. This application
has
generally been accomplished using oxides, sulfates, oxysulfates, chelates, and
other
fonnulations.
In ordinary agricultural soil, pH's vary from about 4.5 to 8.3. Soils having
pH's
below 6.5 are normally subjected to liming to bring the pH of the soil to
neutral or near-
neutral. Liming is necessary for the availability of many macronutrients (such
as
nitrate, phosphates, magnesium, and especially'calcium). However, when lirne
is
applied, the availability of micronutrients is generally decreased due to the
formation
of insoluble products. This is especially true if over-liming occurs.
Similarly, fields
with naturally occurring pH's in excess of 7 have restricted availability of
micronutrients due to the formation therein of insoluble reaction products
(fixation).
It is known that the availability of most micronutrients increases as the pH
decreases.
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In the past it has been impractical to utilize the knowledge that an acid
environment can
provide enhanced availability of micronutrients. One reason is that, although
micronutrient availability is enhanced by low pH's, maximum crop yields are
normally
obtainable at higher pH's.
In order to compensate for the lack of available micronutrients, many farmers
apply excess amounts of fertilizers containing those micronutrients to the
soil. Farmers'
may however apply expensive foliar applications which may solve the problems,
but
at a high cost to the farmer. The micronutrients (which are generally fixed or
become
unavailable when applied to soils) often limit the uptake of the
macronutrients. The
macronutrients may then wash off or leach out of the soil and contaminate the
groundwater or surface water.
SUMMARY OF THE INVENTION
The instant invention overcomes the problems described above by combining
ammonium sulfate, elemental sulfur, and micronutrients into compositions
capable of
providing an acid-forming microenvironment in soil, without decreasing the
overall
bulk soil pH. Preferably, the compositions are granular in form to provide the
low pH,
high micronutrient uptake soil microenvironments. Alternately, if it is
desirable to
decrease the overall bulk soil pH, non-granulated compositions (i.e., a fine
particle
mixture) can be used.
In more detail, the micronutrient compositions of the invention (both
granulated
and non-granulated) comprise ammonium sulfate, elemental sulfur, and a
micronutrient
selected from the group consisting of zinc, iron, manganese, copper, boron,
cobalt,
vanadium, selenium, silicon, nickel, and mixtures thereof. Prefened
micronutrients are
zinc, boron, iron, copper, and manganese, with zinc, boron, iron, and
manganese being
particularly preferred. The preferred ranges of concentrations of each of the
components of the compositions are set forth in Table 1.
While the non-granulated composition itself is useful for decreasing the
overall
pH of the bulk soil, it is a particular advantage of the instant invention
that the
composition can be formed into granules for situations where it is desirable
to decrease
the pH in only small portions of the soil, while not affecting the overall
bulk soil pH.
Broadly, granulated composites in accordance with the invention can be formed
by
granulating a mixture comprising ammonium sulfate, elemental sulfur, and a
micronutrient selected from the group consisting of zinc, iron, manganese,
copper,
boron, cobalt, vanadium, selenium, silicon, nickel, and mixtures thereof. The
granulation of the mixture can be carried out using any known granulation
method.
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One preferred method of fonning granulated composites in accordance with the
invention involves mixing ammonium sulfate, elemental sulfiu, and the desired
micronutrient(s) to form a mixture, and then adding a chemical reactant to the
mixture.
Suitable chemical reactants include sulfuric acid, phosphoric acid, or
anhydrous
ammonia (or any chemical reactant which will react with the mixture to
generate heat
and thus initiate a chemical binding reaction). The resulting mixture is then
processed -
in any granulation machinery known in the art, including but not limited to
rotary dram
granulators, rotary pan granulators, fluid bed granulators, or prilling
towers. As the
chemical reactions proceed, the granules will harden.
If a physical granulation method is preferred, the same procedure can be
followed as described above for chemical granulation with the exception that,
instead
of adding a chemical reactant to the mixture, a binding agent (such as
lignosulfonates
or attapulgite clay) is added to the mixture. If the use ofphysical or
chemical binding
agents is not desirable, the anunonium sulfate, elemental sulfur, and desired
micronutrient(s) can be ground to a relatively fine mesh size (generally from
about
0.005 mm to about 1.0 mm) and mixed together. The resulting mixture is then
processed through rollers exerting pressures onto the mixtures of from about
20,000 to
about 60,0001bs/inz. The sheets or ribbons of processed material are broken
into small
pieces by a chain mill or other device. These pieces can then be screened into
groups
of uniform sizes before drying.
The preferred micronutrients and the preferred concentration ranges of the
components making up the granulated composites are the same as those described
for
the non-granulated composites above. The micronutrient granules of the instant
invention should have a bulk density of from about 30-100 lbs/ft3, preferably
from
about 45-851bs/ft , and more preferably about 60 lbs/ft3. The granules should
have a
water solubility of from about 10-100%, preferably from about 20-95%, and more
preferably from about 25-90%. The largest surface dimension of the granules is
preferably from about 0.1-30 num, more preferably from about 0.1-3.0 mm, and
most
preferably from about 1.5-3.0 mm. While these ranges are preferred, those
skilled in
the art will recognize that the granule size can be varied according to the
crop with
which it will be used.
The granulated and non-granulated composites of the invention can be applied
to the soil by any method known in the art which suits the needs of the
fartner,
including bybroadcast application, banded application, sidedress application,
with-the-
seed applications, or any combination of these application methods.
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While the non-granulated compositions will decrease the overall bulk soil pHõ
the granulated composites provide intimate contact between the components of
the
granules, resulting in a unique, localized acid microenvironment that
increases the
availability of the micronutrients (i.e., zinc, iron, manganese, copper,
boron, cobalt,
vanadium, selenium, silicon, nickel). When applied to the soil as a
fertilizer, the
microenvironment will have a pH distinct from the pH of the bulk soil
surrounding the
miaroenvironment. As the plant roots randomly grow throughout the soil, they
will
encounter these microenvironments, allowing access to the readily available
micronutrients while simultaneouslypermitting the roots to absorb
othernutrients (such
as nitrogen or phosphorous) from the non-acidified bulk soil surrounding the
microenvironment.
When the granulated composites of the invention are applied to soil, the
resulting rnicroenvironments should have a soil pH of from about 3-7,
preferably from
about 4-6, and more preferably from about 5-6. Expressed another way, the pH
within
the microenvironments should be from about 1-4, and preferably from about 2-3
pH
units lower than the pH of the bulk soil (i.e., soil surrounding the
microenvironments
but whose pH has been essentially unaffected by the granules). The pH of the
microenvironment should remain acidic (i.e., pH of less than 7) for at least
about 30
days, preferably at least about 60 days, and more preferably for from about 90-
120 days
after the granule has been contacted with the soil. The granulatefl composites
can be
randomly distributed throughout the soil (as are the roots of the growing
plants),
however, it is preferred that the granulated composites be distributed in a
quantity such
that a sufficient number of low pH microenvironments are formed to allow an
adequate
number of plant roots to contact the microenvironment, and thus access the
readily
available micronutrients. Therefore, it is preferred that there be from about
1-100
microenvironments per cubic foot of soil, more preferably from about 10-50
microenvironments per cubic foot of soil, and most preferably from about 12-40
microenvironments per cubic foot of soil. Preferably, the microenvironments
(forrned
by granules whose largest surface dimensions are from about 1.5-3.0 mm) are of
such
a size that the largest dimensiona of the microenvironment average from about
5-10
mm, more preferably from about 4-8 mm, and mpst preferably from about 3-6 mm.
Because the microenviromnents are acidic, the micronutrients from the granules
are more readily available, and thus are more efficiently taken up by the
plant roots.
Those skilled in the art will appreciate that this efficiency allows for a
substantial
decrease in the quantity of micronutrients required, saving money for the
farmer.
Specifically, use of the granulated composites in accordance with the methods
of the
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invention results in a decrease of at least about 25% by weight per acre,
preferably at
least about 35% by weight per acre, and more preferably at least about 50% by
weight
per acre, in the quantity of at least one of the micronutrients within the
composites in
comparison to the quantity of the respective micronutrient which would be
required
5 using compositions and methods known in the art.
Table 1
CoZnponent Broad Range' Pref '
ammonium sulfate 5-49% by wt. 10-25% by wt.
elemental sulfur 2.5-49% by wt. 5-25% by wt.
zinc 0.02-74% by wt. 1-40% by wt.
manganese 0.02-55% by wt. 2-40% by wt.
copper 0.02-74% by wt. 1-40% by wt.
iron 0.02-55% by wt. 1-40% by wt.
boron 0.02-18% by wt. 0.05-12% by wt.
nickel 0.015-0.025% by wt. 0.01-0.02% by wt.
cobalt 0.002-0.02% by wt. 0.005-0.01 % by wt.
silicon 1-25% by wt. about 20% by wt.
selenium 0.005-.2% by wt. about 0.125% by wt.
vanadium 0.005-.2% by wt. about 0.09% by wt.
sulfuric acid 5-25% by wt. 10-15% by wt.
Approximate percent by weight, based upon the total weight of the composition
taken as 100% by
weight.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXA V! LES
The following examples set forth preferred methods in accordance with the
invention. It is to be understood, however, that these examples are provided
by way of
illustration and nothing therein should be taken as a linutation upon the
overall scope
of the invention.
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EXAMPLE I
Preparation of a 200/o Copper Ivlicronutrient Composition
The following ingredients were added to a rotary drum granulator and raixed
until substantially homogeneous: 400 lbs of ammonium sulfate; 818 lbs of zinc
oxide
reactant (10% zinc); 432 lbs copper oxide; and 200 lbs elemental sulfur. After
mixing,
286 lbs of sulfaric acid was added to the mixture in the granulator to form a
semi-liquid -
slurry. The granulator (which was angled with its mouth positioned slightly
above the
horizontal) was then rotated in order to form the slurry into granules. As the
granules
reached the appropriate size, they rolled out of the mouth of the granulator
drum. The
formed granules were heated in a dryer (to approximately 200-250 F) causing
the
excess moisture to evaporate and hardening the granule. After drying, the
granules
were passed over a series of vibrating screens in order to obtain only
granules having
a size of from 1.5-3.0 mm. The granules outside this size range were then
crushed and
reprocessed as described above. Those granules having the appropriate sizes
were then
sprayed with a coating of lignosulfonate in order to increase hardness and
reduce dust
formation.
EXAMI'LE 2
Preparation of a 20% Zinc Micronutrient Composition
The following ingredients were mixed in a pug mill mixer mixed until
substantially homogeneous: 400 lbs of ammonium sulfate; 854 lbs of zinc oxide
reactant (10"/o zinc); 397 lbs zinc oxide (76% zinc); and 200 lbs elemental
sulfur. The
resulting mixture was added to a rotary drum granulator, followed by the
addition of
286 lbs of sulfuric acid to the granulator. All of the ingredients were mixed
in the
granulator until a semi-liquid slurry was formed. The granulator was then
rotated in
order to form the slurry into granules, which then exited the mouth of the
drum
(positioned slightly above the horizontal). The formed granules were heated in
a dryer
(to approximately 200-250 F) evaporating the excess moisture and hardening the
granules. After drying, the granules were passed over a series of vibrating
screens in
order to obtain granules having a size of at least 3.0 mm. The granules
outside this size
range were then crushed and reprocessed as desaribed above. Those granules
having
the appropriate size were sprayed with a coating of lignosulfonate.
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EXAMPLE 3
Tests were conducted to detennine the effects of various micronutrient
combinations on soil pH's and micronutrient uptakes by soybeans. Those
combinations
were: anunonium sulfate with a micronutrient mix; elemental sulfur with a
micronutrient mix; and a combination of ammonium sulfate and elemental sulfur
with
a micronutrient mix. The micronutrient mixes contained Zn, Fe,1Vin, and Cu in
such-
amounts that the following quantities of each were applied per acre: 1 lb Zn,
0.5 lb Fe,
0.5 lb Mn, and 0.51b Cu. In each run, twenty pounds of sulfur was applied to
each acre
of soil. The sulfur applied in each run was obtained in the following
variations: twenty
pounds of sulfur from (NH4)2SO4; twenty pounds of sulfur that was elementaI
sulfur;
and a combination of ten pounds of sulfur from (NH4}~SO4 and ten pounds of
sulfur that
was elemental sulfur. Each combination was applied to the soil by banded
applications
at planting. The soil pH and leaf tissue was tested at 60 days after planting.
The results
from these tests are set forth in Table 2 below. Treatment (III) decreased the
soil pH
0.5 units more than treatment (I), and treatment (III) decreased the soil pH
1.2 units
more than treatment (II}. This in turn led to a large increase in the uptake
of Zn, Fe,
Mn, and Cu by the plant subjected to treatment (III) in comparison to those
plants
subjected to treatments (1) or (II).
Table 2
Soybean Uptake - ppm
Treatment Soil pH Zn Fe Mn Cu
Control 7.4 37 70 48 5
(1) 20 lbs. from (NH4)2S0' 6.1 42 98 73 7
(II) 201bs. from Sb 6.8 39 84 57 6
(III) 201bs. Combination 5.6 49 160 82 9
wenty pounds of sulfur per acre, with the sulfur being obtained from
(NH,,)zSO,.
ITwenty pounds of sulfur per acre, with the sulfiu being elemental sulfur.
'Twenty pounds of sulfur per acre, with ten pounds of the sulfur being
obtained from (NH4)2SO4 and ten
pounds of the sulfiu being elemental sulfiir.
