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Compositions of and a method for preparing polymeric formulations that gradually, continuously and uniformly release various compounds over a long period of time in ionic form that are well recognized as essential to the growth of agricultural commodities. The compounds, such as inorganic salts of v

Compositions of and a method for preparing polymeric formulations that gradually, continuously and uniformly release various compounds over a long period of time in ionic form that are well recognized as essential to the growth of agricultural commodities. The compounds, such as inorganic salts of varying water solubilities, are monolithically incorporated in a thermoplastic polymeric matrix usually of two thermoplastic polymers, for example, a copolymer of poly(ethylene-vinyl acetate) or a copolymer of ethylene and propylene. Release is generally conditioned upon the presence of moisture and is proportional to the moisture content of soil treated with the subject invention. Release rate is tailored to a given desirable condition by regulation of the free volume and/or porosity within the polymer matrix and through dispenser geometry. Free volume is maintained at the level conducive to agent release such as through the use of free volume modifying secondary thermoplastic additives such as low density polyethylene; and porosity is controlled through the use of porosity enhancing agents appropriately termed porosigens. Said porosigens can be the low or moderate soluble salts such as the carbonates, bicarbonates, sulfates, phosphates, nitrates, etc.; of the alkali metals, the alkaline earths, or ammonium. Upon exposure to moisture, water ingress into the dispensing pellet removes said porosigen through dissolution processes thus creating a porous network permitting water contact with the incorporated nutrient molecules and their gradual egress in said water over a period of time such as for about a couple months to four years, or longer.

대표청구항 ▼

A controlled release plant nutrient dispenser comprising: a uniformly dispersed admixture of a plant nutrient, a porosigen, and 100 parts by weight of a polymer matrix, said polymer matrix made from a compound selected from the class consisting of an ethylene-vinyl acetate copolymer, an ethylene-pro

A controlled release plant nutrient dispenser comprising: a uniformly dispersed admixture of a plant nutrient, a porosigen, and 100 parts by weight of a polymer matrix, said polymer matrix made from a compound selected from the class consisting of an ethylene-vinyl acetate copolymer, an ethylene-propylene copolymer, a low density polyethylene, and combinations thereof; the amount by weight of said ethylene constituent in said ethylene-vinyl acetate copolymer ranging from about 60 percent to about 95 percent, the weight average molecular weight of said ethylene-vinyl acetate copolymer ranging from about 40,000 to about 400,000; the amount by weight of said ethylene constituent in said ethylene-propylene copolymer ranging from about 30 percent to about 75 percent, the weight average molecular weight of said ethylene-propylene copolymer ranging from about 50,000 to about 250,000; said plant nutrient being required in minute amounts by a plant, the amount of said plant nutrient ranging from about 10 to about 160 parts by weight per 100 parts of said polymer matrix, the amount of said porosigen ranging from about 0.1 to about 70 parts by weight per 100 parts of said polymer matrix, said porosigen having a solubility of less than 100 grams per 100 grams of water so that upon contact of said dispenser with soil moisture, the plant nutrient is released at a rate required by the plant to stimulate growth.