Abstract:
In order to investigate the nutrient decayed and released rules, the nylon mesh bag method was used to monitor the nutrient releases from the manures of Huai bean, soybean and mungbean to soil in 287 days. The results show that all these green manures have an initial rapid decaying and then a slow decaying, and peak in the first month. During the stable phase, Huai bean has higher residual ratio than those of soybean and mungbean. The releases of different nutrients in green manures are varied. Nitrogen, phosphorus and potassium are released rapidly in the initial 21d, of which the most complete release is potassium. After 287d, the residual ratio of K is 3.2% 5.9%. Calcium in green manures has the highest residual ratio and has no significant change during the decomposition, and the residual ratio of Ca is 74.8% -89.8% after 287d. After 28-days fast release, the residual ratio of Mg drops to approximate 30%. The residual ratio of copper undulates. There is significant release of iron within the first 21d, and follows by a long slow release period. The residual ratio of zinc declines in the first 49d, remains steady from 49d to 175d, and decreases dramatically after 175d. The residual ratio of manganese shows a downward trend during the decaying period and reduces to 67.3% -74.1% after 287d, which is just less that that of calcium. Differences of nutrient release status of three green manures depend on nutrients. The residual ratios of nitrogen, calcium, iron, copper and zinc vary among three green manures while no significant differences of the residual ratios of potassium and magnesium are found among them. Mungbean has the lowest residual ratios of all nutrients except C, N, Cu and Zn, while soybean has the highest residual ratios of all nutrients except C, N, Cu and Fe.