MXPA99004390A - Fertilizer compositions including chelated metal ions - Google Patents

Abstract

The present invention is directed to fertilizer additives and compositions, and to methods for their preparation and administration to plants. The fertilizer additives include chelated metal ions of the transition and alkaline earth metals. The chelated metal solutions are prepared by complexing metal cations using an organic acid and an organic amine. The fertilizer additives include a sufficient quantity of amine to maintain the pH above about 7.5 and preferably about 8-11. While the source of the metal ions may be any biologically acceptable metal salt, the metal oxides are preferred. The preferred chelating agents are citric acid and a difunctional amine. The preferred amines are 2-hydroxyethylamine, dimethylaminopropylamine and mixtures thereof. Additive solutions containing such chelated metals are stable at alkaline pH and are used to prepare clear, liquid fertilizer compositions for delivery of trace metals to plants.

Description

FERTILIZING COMPOSITIONS THAT INCLUDE CHELATING METALLIC IONS DESCRIPTION OF THE INVENTION The present invention is generally related to fertilizer additives and fertilizer compositions and to methods for their preparation and use. More specifically, the present invention is directed to compositions and fertilizer additives that include metal chelating ions to provide micronutrients necessary for the growth of plants. Agriculturally, metal ions are essential nutrients for the growth of plants. The deficiency of the earth due to unavailability or depletion of metal ions is very often the cause of the deficient growth of the plants. Deficiencies of crops occur at extremely low levels of metal deficiency, that is, at parts / million levels in the plant tissue. Both the application of soil and foliar metal chelating ions can prevent, correct or minimize crop deficiencies. Chelating complexes have been favored because metal chelating ions remain soluble in different or changing environments. See Chen and Barak, Advancer in Agronomy, vol. 35, pp. 217-239 (1982). Conventional products have used synthetic chelates. However, although it has been widely accepted as the best method for the administration of metal ions, the production of synthetic chelates is very expensive. See, Barak and Chen, Soil Sci. Soc. Am. J., vol. 51, pp 893-896 (1987). Accordingly, conventional metal chelating additives are expensive. Therefore, less expensive but efficient chelating systems have been sought. The use of citric acid as a chelating agent has been proposed to provide a cheap alternative that occurs naturally. However, it has been shown that metal chelates of citric acid are unstable at a pH above 7. See, Cune, et al, Soil Sci. Soc. Am, J., vol 46, pp. 1158-1164 (1982) and U.S. Pat. No. 5, 372, 626. Prior methods for the chelation of metal ions for agriculture also propose the introduction of inorganic anions to stabilize the pH.

However, these anions may have been associated with ecological damage and their addiction adds fertilizer expense. Consequently, for many years there has been a need that has not been satisfied to obtain more environmentally friendly and more economical and efficient fertilizer compositions and additives to provide levels of micronutrients of trace metals to the plants and for production methods. such fertilizers with the required metallic nutrients necessary for the growth of the plant. The present invention solves those needs. The present invention is directed to novel fertilizer additives and compositions useful for providing trace levels of metal ions to the plant tissue in chelating form at a neutral pH. These additives and compositions are prepared using a novel combination of chelating agents to form metal ion complexes and to control the pH of the additive solution. While metals can be provided by any salt, metal oxides are a preferred source of metals. The methods of the present invention for the conversion of metal salts, preferably oxides, to metal chelating solutions are unique in the manner in which they can produce inorganic anion-free compositions frequently associated with chelating systems. Although the scope of the present invention is not limited as long as the present method will also chelate metal ions of chloride, sulfate, nitrate, hydroxide and carbonate and other biologically compatible salts of cations, these salts are more expensive per unit of metal cation, commonly less pure, and have been associated with ecological damage. Metal oxides are preferred because they are significantly less expensive per unit of metal cation, are usually purer, and are less toxic to the environment than their inorganic anion counterparts.Metal ions are chelated using an organic acid and an organic amine In the preferred compositions of the present invention metal cations form complexes using citric acid and a sufficient amount of a dysfunctional amine to maintain the pH of about 7.5.The dysfunctional amine offers several advantages over existing technologies, for example, odorless formula, the formulator's ability to regulate buffer solutions with a basic pH, and better safety The difunctional amine not only neutralizes the excess acid in the solution, but also participates in the formation of the chelating complex to create a more stable complex It is a general aspect of the present invention to provide a formula for obtaining a fertilizer additive. liquid, of course, comprising water, an organic acid, preferred easily selected from carboxylic acids having from about 2 to about 20 carbon atoms, at least one metal salt wherein the metal is preferably selected from the group consisting of the transition metals and alkaline earth, and an organic amine which preferably having from about 1 to about 20 carbon atoms. The organic amine is more preferably selected from the group of dysfunctional amines consisting of the organic diamines, hydroxy amines, polyamines, polyhydroxy amines and mixtures thereof. In the presently most preferred embodiments the present invention provides compositions and methods for chelating metal ions of their metal oxides wherein the metal is selected from the group consisting of calcium, magnesium, iron, cobalt, copper, zinc, molybdenum and mixtures thereof. , using citric acid and a dysfunctional amine selected from the group consisting of 2-hydroxyethylamine, dimethylaminopropylamine and mixtures thereof. The amine is preferably present in an amount sufficient to maintain the pH of the additive above about 7.5, preferably about 8-11. Such additive fertilizer solutions can generally be referred to hereinafter as "fertilizer additives" or "additive solutions". It is another aspect of the present invention to provide a clear liquid fertilizer composition which is composed of the above additive fertilizer solutions mixed with a liquid fertilizer. Any conventional liquid fertilizer can be used. Typical liquid fertilizers include N-P-K fertilizers selected from the group containing at least one nutrient selected from the group consisting of nitrogen, phosphorus and potassium. In the present invention, the fertilizer compositions are preferably formulated so that the metal concentration of the additive solution is from about 0.001 to about 5.0 percent by weight in the final fertilizer composition. The final fertilizer compositions will typically have a neutral or slightly basic pH. It is another aspect of the present invention to provide a method for formulating clear liquid fertilizer compositions comprising fertilizer additives containing complex metal cations. The preparation includes complex metal cations in an acid solution of water and an organic acid, preferably citric acid. The metal's preferred source of ions is metal oxides. The solution of the complex metal ions is stabilized and is quenched by the addition of a sufficient amount of organic amine to maintain the pH above 7.5, more preferably about 8-11. Preferred organic amines are dysfunctional amines selected from the group consisting of diamine, hydroxyamine, polyamine, polyhydroxyamine, and mixtures thereof. The most preferred amines are 2-hydroxyethylamine, dimethylaminopropyl ina and mixtures thereof. The additive solutions with adjusted pH are then mixed with liquid fertilizer solutions which contain one of the essential nutrients, ie, nitrogen, phosphorus or potassium. The preferred weight ratios for preparing the liquid fertilizer compositions are from about 1 part additive solution to about 1-10 parts of fertilizer solution. These compositions are preferably formulated to provide from about 0.001 to about 5.0 percent by weight of the metal in the fertilizer composition at a generally neutral pH. The present invention provides a more economical and improved fertilizer composition for providing trace levels of metal ions to the tissues of plants. The compositions and methods of the present invention provide metal chelating ions in an aqueous fertilizer additive. Chelation is achieved using an organic acid and an organic amine. The organic acid can be carboxylic acid, preferably a carboxylic acid having 2-20 carbons. It has been found that e2L citric acid is present in most of the preferred organic acids mainly because of its low cost and abundant availability, thereby relieving the high cost associated with previous synthetic chelators. Citric acid is also preferred due to environmental considerations and other considerations, for example odor.

Preferred organic amines have from about 1 to about 20 carbon atoms. The most preferred organic amines are the dysfunctional amines selected from the group consisting of organic diamines, hydroxy amines, polyamines, polyhydroxy amines and mixtures thereof. The most preferred organic amines are the dysfunctional amines selected from the group consisting of 2-hydroxyethylamine, dimethylaminopropylamine and mixtures thereof. The organic amine, preferably the dysfunctional amine, should be present in the fertilizer additive in an amount sufficient to maintain the pH of the additive solution per enzyme of about 7.5 preferably at a pH of about 8-11. Broadly, metal ions in the fertilizer additive can be metals in biologically required traces. The metal ions in the additive solution are typically selected from the group consisting of transition metals and alkaline earth. Preferred compositions include at least one metal selected from the group consisting of calcium, magnesium, manganese, iron, cobalt, copper, zinc, molybdenum and mixtures thereof. While metal ions can be provided by any salt soluble in the aqueous acid / amine solution, the preferred source of metal ions is metal oxides. While the metal may be present in any amount, it is preferred that the additive fertilizer solution contains about 0.1 to about 15.0 percent by weight of metal ions. In the present invention additive fertilizer solutions are mixed with conventional liquid fertilizers to produce clear liquid fertilizer compositions. Liquid fertilizers are chosen from the group of fertilizers that contain at least one nutrient selected from the group consisting of nitrogen, phosphorus and potassium. These liquid fertilizers are commonly referred to as "N-P-K fertilizers". A sufficient amount of the additive solution is mixed with the selected liquid fertilizer so that the concentration of the metal complex supplied by the additive solution is from about 0.001 to about 5.0 percent by weight in the final fertilizer composition. This mixture is typically achieved when the ratio of the weight of the fertilizer additive to the liquid fertilizer is from about 1 part of additive to about 1-10 parts of the liquid fertilizer. The fertilizer additive compositions according to the present invention can be prepared with the following method. In acidic solutions it is preferred to add an organic acid to water. The preferred organic acids are selected from the group of carboxylic acids having from about 2-20 carbon atoms. The most preferred carboxylic acid is citric acid. A metal salt, preferably oxide, selected from the salts of metals in biologically required traces, preferably transition metals and alkaline earth, is dissolved in the acid solution. The acid solution containing metal ions is then quenched by adding a sufficient amount of an organic amine to raise the pH of the solution to at least about 7.5, preferably about 8-11. The solution resulting from the complex metal ions is typically clear and free of any precipitation. It has been found that these solutions are very stable and provide excellent liquid fertilizer additives useful for providing trace metals to the plant tissue. The liquid fertilizer additive solution is then mixed with a conventional liquid N-P-K fertilizer. The resulting fertilizer composition is also typically a clear liquid fertilizer solution that preferably contains from about 0.001 to about 5.0 percent by weight of metal and has a neutral pH. The fertilizer compositions described above and / or prepared according to the above methods can be applied to the soil surrounding the plant or to the foliage of the plant by conventional methods to provide trace metals easily absorbed by the plant tissue. In this way the compositions and fertilizer additives of the present invention, particularly when using metal oxides, provide an environmentally friendly and economical source of trace metals for use in a wide range of applications in agriculture. The above description of the present invention is susceptible of a very broad application utility. It is therefore easily understood by those skilled in the art that many embodiments and adaptations of the present invention other than those described herein will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. With the above description of the present invention, it is believed that any person reasonably skilled in the art will be able to prepare and use the chelating metal ion compositions described herein. For purposes of illustration, but without limiting the scope and substance of the present invention, the following examples describe various specific embodiments for fertilizer compositions prepared in accordance with this invention. Example 1 A fertilizer additive containing 9% chelating zinc was prepared by adding 1935 grams of 2-hydroxyethylamine to 2000 grams of water. To this solution was added 1256 grams of zinc oxide, followed by 2943 grams of citric acid. The solution was stirred. After allowing the solution to cool sufficiently, 2796 grams of water were added to dilute the solution to 9% zinc. The resulting solution was light yellow and had a pH of 9. The additive solution was then added to a conventional liquid N-P-K fertilizer to provide clear fertilizer compositions. Example 2 A fertilizer additive containing 6% molybdenum (II) was formulated by adding 32 grams of citric acid to 114 grams of water. To this solution was added 14 grams of molybdic oxide with stirring. Later, 32 grams of 2-hydroxyethylamine and 4 grams of dimethylaminopropylamine were added to produce a clear chelating solution Mo (II) with a pH of 7.8. This additive was added to conventional liquid N-P-K fertilizers to produce clear fertilizer composition. Example 3 A fertilizer additive containing 5% manganese was prepared by adding 360 grams of citric acid to 1181 grams of water. After the citric acid was dissolved, 128 grams of manganese oxide (II) was added to the mixture and the reaction was allowed to form manganese citrate, in an insoluble, whitish precipitate very lightly pink. After the precipitate formed, 320 grams of 2-hydroxyethylamine and 10 grams of dimethylaminopropylamine were added. The precipitate was dissolved to produce a clear 5% manganese chelating solution having a pH of 10.8. This additive was added to a conventional liquid N-P-K fertilizer to produce clear fertilizer compositions. Example 4 A 3 percent yellow magnesium fertilizer additive was prepared by dissolving 500 grams of citric acid in 920 grams of water. To this solution was added 100 grams of magnesium oxide with stirring. Then 440 grams of 2-hydroxyethylamine and 40 grams of dimethylaminopropylamine were added. The resulting additive solution was a 3% yellow, clear chelating magnesium solution with a pH of 8. This fertilizer additive was added to conventional liquid N-P-K fertilizers to produce a clear fertilizer composition. Example 5 A fertilizer additive containing 5% ferrous iron was prepared by dissolving 400 grams of citric acid in 690 grams of water. Then 500 grams of ferrous sulfate was added to the mixture. Slowly, they were added by mixing 400 grams of 2-hydroxyethylamine and 10 grams of dimethylaminopropylamine in the mixture. A dark green chelating solution of ferrous iron 5% with a pH of 8 was produced. This fertilizer additive was added to conventional liquid N-P-K fertilizers to produce clear fertilizer compositions. Example 6 A fertilizer additive containing 5% copper was produced by adding 310 grams of citric acid to 1210 grams of water. To this mixture was added 190 grams of tribasic copper sulfate. Later, 280 grams of 2-hydroxyethylamine were slowly added to produce a dark blue solution having a pH of 8. The fertilizer additive was added to conventional liquid N-P-K fertilizers to produce clear fertilizer compositions. Example 7 A 5% chelating cobalt fertilizer additive was prepared by adding 360 grams of citric acid to 840 grams of water. After the citric acid was dissolved, 440 grams of cobalt sulfate was added to the mixture. Later, 320 grams of 2-hydroxyethylamine and 40 grams of dimethylaminopropylamine were added to the solution. The resulting solution was a clear dark purple solution with a pH of 8.7. This fertilizer additive was added to conventional liquid N-P-K fertilizers to produce clear fertilizer compositions. Example 8 A 5% copper fertilizer additive was produced by adding 156 grams of citric acid to 422 grams of water.

To this solution was added 197 grams of copper sulfate heptahydrate. Then 200 grams of 2-hydroxyethylamine were slowly added to produce a dark blue solution with a pH of 7.6. This fertilizer additive was added to a conventional liquid N-P-K fertilizer to produce clear fertilizer compositions. Example 9 A 12% zinc fertilizer additive was produced by adding 250 grams of citric acid to 300 grams of water.

To this mixture was added 150 grams of zinc oxide.

Then, 300 grams of 2-hydroxyethylamine were slowly added to produce a clear yellow solution with a pH of 9. This fertilizer additive was added to a conventional liquid N-P-K fertilizer to produce clear fertilizer compositions. Example 10 A 3% light yellow magnesium fertilizer additive was prepared by dissolving 250 grams of citric acid in 214 grams of water. Then, 286 grams of magnesium sulfate heptahydrate were slowly added to the solution. Then 250 grams of 2-hydroxyethylamine were added. The resulting additive was a 3% clear yellow chelating magnesium solution having a pH of 8. This fertilizer additive was then added to a conventional liquid N-P-K fertilizer to produce clear fertilizer compositions. Example 11 A transparent dark green fertilizer additive containing 4.5% zinc, 1% manganese, 1% copper and 1% iron was prepared by dissolving 200 grams of citric acid in 464 grams of water. To this solution was added slowly with stirring, 13 grams of manganese oxide, 56.5 grams of zinc oxide, 36 grams of a 13 * 5 ferric chloride solution and 28 grams of copper chloride. Then 200 grams of 2-hydroxyethylamine and 20 grams of dimethylaminopropylamine were added. The resulting product was a dark green transparent solution. This fertilizer additive was then added to a conventional liquid N-P-K fertilizer to produce clear fertilizer compositions. Example 12 A chelating solution was prepared by adding 40 grams of citric acid to 120 grams of water. After the acid was dissolved, 40 grams of 2-hydroxyethylamine were stirred in the solution. To 100 grams of chelating solution was added 400 grams of a 10% caustic solution. 2 grams of a 13% ferric chloride solution and 1 gram of calcium hydroxide were then added to the solution. This produced a clear metallic chelating solution which can be added to conventional liquid N-P-K fertilizers to produce clear fertilizer compositions. In an alternative procedure, the addition of ferric chloride, calcium hydroxide and caustic solutions without the chelating solution resulted in the production of a precipitate in the fertilizer additive. . The subsequent addition of the chelating solution containing the organic acid and amines will produce a clear fertilizer additive. The compatibility between the additive solution and the liquid fertilizer is = essential. If the metal cations are not sufficiently chelated then insoluble salts will form. Tests were performed by mixing various liquid fertilizers with additive chelating solutions made using the above methods of the present invention. The chelants in the following table formed complexes with citric acid and were buffered with 2-hydroxyethylamine. The results of this compatibility test are set forth in Table 1.

Fertilizer Iron Zinc Manganese Mix Copper Molybdenum Cobalt Liquid Iron1 (II) (lll) 1 1 -37-0 Light Clear Light Clear Light Clear 4-11-11 Light Clear Clear Light Clear Light 32-0-0 Light Clear Clear Clear Clear Clear Light Clear Clear 12-0-0.26S Clear Clear Clear Clear Clear Clear (Red) Clear Clear Clear Clear Clear Clear DAP Clear produced 1ll-37-0 ammonium polyphosphate 4-11-11 ammonium polyphosphate, potassium chloride 32-0-0 ammonium nitrate, urea 12-0-0, 26S-ammonium nitrate, ammonium thiosulfate DAP-diammonium phosphate (orthophosphate) The foregoing description of the invention has been mainly directed to the particular preferred embodiments according to the requirements in the patent statutes. and purposes of explanation and illustration. It will be apparent, however, to those skilled in the art, that many modifications and changes in the methods specifically described can be made without departing from the true scope and spirit of the invention. For example, while citric acid and a dysfunctional amine are preferred, other organic acids and amines may be used. In fact, soluble salts of organic acids can be used in place of acids. Also, while it is preferred to dissolve the metal salt in an aqueous solution of the organic acid to which the amine is then added, the order of the additives does not appear to be critical. Therefore, the invention is not restricted to the preferred embodiments described and illustrated but covers all modifications which may fall within the scope of the following claims.

Claims (26)

1. CLAIMS 1. A liquid fertilizer composition, characterized in that it comprises: water; citric acid; a dysfunctional amine selected from the group consisting of 2-hydroxyethylamine, dimethylaminopropylamine and mixtures thereof; at least one metal oxide wherein said metal is selected from the group consisting of calcium, magnesium, manganese, iron, cobalt, copper, zinc, molybdenum and mixtures thereof; and a liquid fertilizer solution including at least one nutrient selected from the group consisting of nitrogen, phosphorus and potassium.
2. 2. The fertilizer composition according to claim 1, characterized in that the metal forms a complex with the citric acid and the dysfunctional amine.
3. 3. The fertilizer composition according to claim 2, characterized in that said complex was formed in an aqueous solution of the citric acid and a sufficient quantity of the amine to maintain the pH of said solution above 7.5.
4. 4. The fertilizer composition according to claim 3, characterized in that it comprises a mixture of such aqueous solution, such liquid fertilizer solution in a weight ratio of about 1 to 10 parts of liquid fertilizer solution for each part of aqueous solution.
5. 5. The fertilizer composition according to claim 1, characterized in that said composition contains from about 0.001 to about 5.0% percent by weight of the metal.
6. 6. The fertilizer composition according to claim 1, characterized in that it has a pH of about 7.0.
7. 7. A liquid fertilizer additive, characterized in that it comprises: water; ~ an organic acid; at least one metal salt wherein said metal is selected from the group consisting of transition metals and alkaline earth; and a sufficient amount of an organic amine to maintain the pH of the additive at about 7.5.
8. 8. The liquid fertilizer additive according to claim 7, characterized in that the metal salt is a metal oxide.
9. 9. The liquid fertilizer composition according to claim 7, characterized in that said metal is selected from the group consisting of calcium, magnesium, manganese, iron, cobalt, copper, zinc, molybdenum and mixtures thereof.
10. 10. The liquid fertilizer additive according to claim 7, characterized in that the organic acid is selected from carboxylic acids having from about 2 to about 20 carbon atoms.
11. 11. The liquid fertilizer additive according to claim 10, characterized in that said organic amine has about 1 to 20 carbon atoms.
12. 12. The liquid fertilizer additive according to claim il, characterized in that such an organic amine is a dysfunctional amine selected from the group consisting of organic diamines, hydroxy amines, polyamines, polyhydroxy amines and mixtures thereof.
13. 13. The liquid fertilizer additive according to claim 12, characterized in that such a dysfunctional amine is selected from the group consisting of 2-hydroxyethylamine, dimethylaminopropylamine and mixtures thereof.
14. 14. The liquid fertilizer additive according to claim 7, characterized in that the pH is about 8-11.
15. 15. The liquid fertilizer additive according to claim 7, characterized in that said additive contains about 0.1 to 15.0 percent by weight of said metal.
16. 16. The liquid fertilizer additive according to claim 7, characterized in that said metal has formed a complex with the organic acid and the organic amine.
17. 17. A liquid fertilizer composition, characterized in that it comprises: a liquid fertilizer solution that includes at least one nutrient selected from the group consisting of nitrogen, phosphorus and potassium; and a sufficient quantity of a selected liquid fertilizer additive of the group consisting of the additives defined by claims 7 to 16 so that the metal concentration of the additive in the composition is from about 0.001 to about 5 percent by weight.
18. 18. The method to provide metal ions to the plants by administering to the soil in which the plants grow or to the foliage of the plant a liquid fertilizer composition selected from the group consisting of defined fertilizer compositions of. . according to claims 1-6 and 17.
19. 19. A method for preparing a liquid fertilizer composition, characterized in that it comprises: adding an organic acid to water to form an acid solution; dissolving a metal salt in the acid solution wherein the metal is selected from the group consisting of transition metals and alkaline earth and mixtures thereof; adding to the resulting solution a sufficient amount of an organic amine to raise the pH of the solution to at least about 7.5; and adding the resulting solution to a liquid fertilizer solution which includes at least one nutrient selected from nitrogen, phosphorus and potassium to produce the liquid fertilizer composition.
20. 20. The method according to claim 19, characterized in that the organic amine is a dysfunctional amine having from about 1 to about 20 carbon atoms.
21. The method according to claim 19, characterized in that such an amine is selected from the group consisting of diamines, hydroxyamines, polyamines, polyhydroxyamines and mixtures thereof.
22. 22. The method according to claim 21, characterized in that the organic acid is citric acid.
23. The method according to claim 19, characterized in that said metal is selected from the group consisting of calcium magnesium, manganese, iron, cobalt, copper, zinc, molybdenum and mixtures thereof.
24. 24. The method according to claim 23, characterized in that the metal salt is an oxide.
25. 25. The method according to claim 23, characterized in that the metal salt is added in an amount sufficient for the concentration of the liquid fertilizer composition to be from about 0.001 to about 5.0 percent by weight.
26. 26. The method according to claim 25, characterized in that such an amine is added in an amount sufficient to maintain the pH of the liquid fertilizer composition between about 8-11.