Evaluation of nutrients release feature of coated controlled-release fertilizer

The nutrient release character of coated fertilizer indicates the strength of controlled releasing and nutrient supply in specific time. At the same time, it can reflect the quality of coated materials and its processing techniques. In this experiment, the nutrition release characters of eight coated fertilizers was evaluated according to the standard recommend by Committee of European Normalization (CEN) using water extraction and soil incubation methods in order to guide the application of coated fertilizers. The test results using soil extraction method showed that there were discrepancies in nutrient release between eight coated controlled fertilizers due to the difference of coated materials and processing techniques. For Compo series, the preliminary solubilityt1 were 51.9%, 28.6% and 11.5%, respectively; differential solubility △t were 1.5%, 1.8%, and 1.4%, respectively; and nutrient release time (T) was ranged from 3 to 6 months. But for Cau series,t1 were 3%, 7.4% and 5.7%, respectively; △t were 0.8%, 1.2% and 1.2%, respectively; and T was ranged from 2 to 3 months. t1 , △t and T of Osmocote were 5.8%, 0.7% and two and a half months, while for Au were 0.9%,2.1% and one and a half month. T of Compo series, Cau series, Osmocote and Au incubated by soil were 2-4, 1.5, 0.7 and 1.3 times of that tested using water extract. Different coated fertilizers were of their respective conversion coefficients, which should be ascertained by concrete calibration experiments. In term of the biomass of cole and corn at sixth week, Osmocote and Au treatments was significantly higher than that of readily available fertilizer, while the biomass of Compo-3 and Cau-C17 treatment were significantly lower. For the other treatments, the biomass didn't show a notable difference with that of readily available fertilizers.