Controlled-release fertilizer compositions

1. A controlled-release fertilizer composition comprising:

coated fertilizer particles each comprising a granule and one or more polyurethane coating layers, wherein the one or more polyurethane coating layers substantially encapsulate the granule; and

wherein the one or more polyurethane coating layers are formed from the reaction product of a hydrophobic aromatic amine polyol composition and an isocyanate curing agent; and

wherein at least one of the one or more polyurethane coating layers comprises inorganic particles.

2. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles comprises two or more polyurethane coating layers, and wherein the innermost of the two or more polyurethane coating layers includes the inorganic particles.

3. The controlled-release fertilizer composition according to claim 1 , wherein the inorganic particles comprise one or more of amorphous silica, clay, fumed silica, calcium carbonate, quartz, aluminum oxide, mica, calcined kaolin, wollastonite, calcite, zirconia, zircon, micaceous iron oxide, iron oxide, aluminum silicates, talc, barium sulfate, or lithopone.

4. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles comprise one or more of a nitrogen compound, a phosphate fertilizer compound, a potash fertilizer compound, a sulfur fertilizer compound, a potassium fertilizer compound, a calcium fertilizer compound, or a metal compound.

5. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles comprise urea.

6. The controlled-release fertilizer composition according to any claim 1 wherein the coated fertilizer particles further comprise one or more of an herbicide, an insecticide, or a fungicide.

7. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles comprise about 1% to about 15%, by weight, of the one or more polyurethane coating layers.

8. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles comprises four polyurethane coating layers.

9. The controlled-release fertilizer composition according to claim 1 , wherein the coated fertilizer particles further comprises a wax coating layer surrounding the one or more polyurethane coating layers.

10. The controlled-release fertilizer composition according to claim 1 , wherein the aromatic amine polyol composition comprises alkylene oxide substituents and wherein the aromatic amine polyol composition further comprises a polyether polyol.

11. The controlled-release fertilizer composition according to claim 10 , wherein the alkylene oxide substituents comprise one or more of ethylene oxide and propylene oxide and wherein the polyether polyol comprises one or more of an ethylene oxide polyol or a propylene oxide polyol.

12. The controlled-release fertilizer composition according to claim 1 , wherein the isocyanate curing agent comprises one or more of a polymeric isocyanate, an aromatic isocyanate, or 4,4′-methylene diphenyl isocyanate.

13. The controlled-release fertilizer composition according to claim 1 , wherein the ratio of the polyol composition to the isocyanate curing agent is about 1:4 to about 1:1.

14. The controlled-release fertilizer composition according to claim 1 , wherein the one or more polyurethane coating layers comprise a catalyst selected from one of an amine-based catalyst or a metal salt catalyst.

15. The controlled-release fertilizer composition according to claim 1 has a nutrient release profile of about 30 days or greater.

16. A method of fertilizing comprising applying the controlled-release fertilizer composition according to claim 1 to soil.

17. A method of making a controlled-release fertilizer composition comprising:

coating granules with a hydrophobic aromatic amine polyol composition;

dispersing inorganic particles onto the polyol composition; and

applying an isocyanate curing agent to the polyol composition to form a polyurethane coating layer substantially encapsulating each granule; and

wherein the polyol composition is miscible with the isocyanate curing agent.

18. The method according to claim 17 , further comprising the formation of one or more additional polyurethane coating layers to substantially encapsulate each granule.

19. The method according to claim 17 , wherein at least one of the one or more additional polyurethane coating layers includes inorganic particles.

20. The method according to claim 17 , wherein the polyol composition and the isocyanate curing agent are included in about a 1:4 ratio to about a 1:1 ratio.