KINETIC OF NUTRIENT RELEASE AND BIODEGRADATION TENDENCY IN SOIL OF SLOW–RELEASED UREA FERTILIZERS WITHIN POLYMER COVER LAYER

Abstract

A slow - release urea fertilizer was prepared by coating polyurethane onto urea granular fertilizer surface to control the release rate of fertilizers can reduce fertilizer's losses and minimize environmental pollution. Granular ureas have been synthesized from conventional urea, bentonite and starch. The sample with ratio of mass of ure: Bentonite: starch is 90: 7,5: 2,5, thickness of polyurethane cover layer is about 30µm containing 5% paraffin wax, release 81.42% N after 90 days in soil (at 25⁰C). The kinetic study showed that the nitrogen release rate from the granular slow-release urea fertilizers  could be represented by pseudo-first-order equation at 25^oC with R²~1. The SEM images showed that polyurethane coating materials had a good biodegradation tendency in soil. Slow - release ure fertilizers do not adversely affect the physical and chemical properties of the soil, they are environmentally friendly.