Traits of Nutrient Release from Starch Acetate Coated Urea Fertilizers in Water

Nitrogen release traits of four kinds urea amended with biological inhibitor and coated by starch acetate(SA) fertilizers in water are examined in laboratory,and comparisons are made to a polyolefin-coated urea(POCU),70 day,made in Japan so that realized the controlling and transforming capacity of every kind starch acetate coated urea fertilizers in this paper.The result indicate that the every curve of the maximum of accumulative urea nitrogen released rate from four starch acetate coated urea fertilizers is converse "L".The time of the maximum of accumulative urea nitrogen released rate from four starch acetate coated urea fertilizers is at 7th-13th days.The date for accumulative urea nitrogen released rates up to 80% from four starch acetate coated urea fertilizers at 2th-3th day.The preliminary solubility rates is 65.71%~75.79%,and accumulative urea nitrogen released rates is low than 75% at 1th-2th day.The differential solubility rate is significantly more 2.5% at 7th day.Accumulative urea nitrogen released rates up to 80% from polyolefin-coated urea is above 40th,and the preliminary solubility rate is 2.05%.Accumulative urea nitrogen released rates from polyolefin-coated urea is 73.32% at 36th day,and 75.01% at 37th day.The differential solubility rate is 1.68% at 7th day.SA-coated urea fertilizers have a little capacity to control the urea nitrogen release,but the controlling capacity of SA-coated urea fertilizers is significantly more inferior than that of polyolefin-coated urea fertilizers,However SA-coated fertilizer efficiently restricts urea nitrogen release rate.The correlation of accumulative urea nitrogen released from SA-coated urea or polyolefin-coated urea fertilizer in water,with time is found to conform to model for a quadric equation in one variable.