Study on characteristics of decomposing and nutrients releasing of three kinds of green manure crops

Green manure is a universal organic fertilizer. Returning the green manure to farmland has been suggested to improve overall soil conditions and to support the agricultural sustainable development. There are many winter fallow fields in south of China, which can be used to plant green manure crops. Common vetch (Vicia sativas L.), Chinese trumpet creeper (Vicia villosa Roth. Var.) and Lathyrus quinquenervius (Lathyrus palustris L. Var. Pilosus ledeb) are the three most popular kinds of leguminous green manure crops, which can be planted extensively in poor soil, especially in drought and low temperature regions. This paper studied the characteristics of decomposing and nutrients releasing of the three kinds of green manure crops by using the method of nylon net bag. The results indicated that the three green manure crops were decomposed fast in the first 15 days after incubation, and the rate of decomposition was more than 50%, then decomposed slowly. The decomposition rate of the common vetch(CV), Chinese trumpet creeper(CTC) and Lathyrus quinquenervius(LQ) were 71.7%, 67.3% and 74.1% at the end of the experiment respectively. Nitrogen(N) and potassium(K) released fast during the first 10 days, while carbon(C) and phosphorus (P) released fast in the first 15 days, then they were all released slowly until the end of experiment. After 70 days incubation, the carbon release rate of the CV, CTC and LQ were 71.3%, 67.0% and 74.1%, respectively. The nutrients release rate of the three green manure was K>P>N, while the K release rate of the three green manure was more than 90%, P release rate was 73.3%-78.7%, N release rate was 59.9%-71.2% after 70 days incubation. The N and P release rates of the LQ were higher than CV and CTC; however, there were no significant difference in K release rate among the three green manure crops. The results also showed that the nutrients release amount of CV and CTC were C>K>N>P, while LQ was C>N>K>P. Nutrients release amount of three green manure crops were different, the release amount of N and C of the LQ were greatest, the release amount of P and K of the CV were highest, all the nutrients release amount of the CTC were the lowest.