Chemistry: fertilizers – Processes and products – Inorganic material
Reexamination Certificate
2000-06-27
2001-04-03
Langel, Wayne (Department: 1754)
Chemistry: fertilizers
Processes and products
Inorganic material
C071S063000, C071S064130
Reexamination Certificate
active
06210459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present 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 utilized when it is desirable to decrease the overall pH of bulk soil.
2. 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 of these 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 formulations.
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 lime 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. 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. Preferred 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. One preferred method of forming granulated composites in accordance with the invention involves mixing ammonium sulfate, elemental sulfur, 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 drum 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 of physical or chemical binding agents is not desirable, the ammonium 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 60,000 lbs/in
2
. 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/ft
3
, preferably from about 45-85 lbs/ft
3
, and more preferably about 60 lbs/ft
3
. 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 mm, 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 farmer, including by broadcast application, banded application, sidedress application, with-the-seed applications, or any combination of these application methods.
While the non-granulated compositions will decrease the overall bulk soil pH, the granulated composites provide intimate contact between the components of the granules, resulting in a unique, localized acid microenvironment that in
Hovey Williams Timmons & Collins
Langel Wayne
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