Coating layer preparation with mixed vegetable oil and nutrient release regulation of fertilizer

Abstract

Mixed vegetable oil (castor oil and hydroxylated soybean oil, MVO) and polymethylene polyphenylene isocyanate (PPI) has been proposed for the coating layer preparation of MVO-based controlled release fertilizer (MCRF). The physicochemical properties and surface morphology of the layer as well as nutrient release characteristics of MCRF were systematically investigated. It was found that molar ratio of MVO and PPI was negatively correlated to the longevity of MCRF. Incensement of mass percentages (MPs) of MVO and core fertilizer could prolong longevity of MCRF. The longevity of MCRF under MMVO/MPPI ratios of 5:4 with the 3% MP reached a maximum value (164.14 ± 2.45 days). The rough surface with more wrinkles in the layer was negative correlation to the initial release rate of nutrient (IRN). A positive relationship between the rough surface with more wrinkles in the layer and the longevity was also observed. The contact angle and surface energy (SE) of the layer had the most obvious effect on the IRN and longevity, especially SE. The modification of molar ratios of MVO and PPI can be considered as a sustainable and cleaner production measure to regulate the nutrient release of MCRF, which will further improve the application of MVO in the future fertilizer field.