The Effect of Polyurethane Multilayer Coating on Nitrogen Release from Controlled Release Fertilizer

Abstract

Nitrogen-based fertilizers are widely consumed to increase productivity since they play an essential role in plant growth. Common commercial fertilizers contain “mobile” nitrogens that can be easily transformed into other nitrogen compounds. The approach method to decrease nitrogen loss is called controlled-release fertilizer (CRF), which is done by modifying fertilizers with coating inhibitors such as polyurethane to provide surface resistance that inhibits nutrient release. Multilayer coating is one of the alternatives to minimize the risk of losing nitrogen content from granular fertilizer. This research will focus on the study of nitrogen release on the CRF modified by various polyurethane coating concentrations (6%, 8%, and 10%). The study was conducted by planting maize plants in a pot inside a greenhouse for nine weeks, followed by a nitrogen release test using a percolator. The morphology of final coating products was observed with scanning electron microscopy, while the mechanical properties and water content were measured with crushing strength test and water stability test. Three weeks after testing, polyurethane can reduce above 60% nitrogen release compared to uncoated fertilizer. After nine weeks since the maizes were planted, the nitrogen release will compare between inside the percolators’ simulation chambers and pot test to see the effect of polyurethane composition with nitrogen release pattern. The results show that the effective composition of polyurethane in CRF products is maximum at 8%w/w with nitrogen released above 75%. Keywords: controlled-release fertilizer, polyurethane multilayer coating, nitrogen release