Abstract:

【Objective】 The sudangrass and ryegrass rotation is a new type of cropping system in the south of China, and it develops very fast in recent years. Guidelines for proper fertilization are needed for improvement of soil fertility in this rotation. 【Method】 The effects of NPK fertilizers on forage yield, sucrase, urease and phosphatase in soil under sudangrass and ryegrass rotation regime were studied based on the four-year fixed location field experiments. 【Result】 The results indicated that the NPK combination significantly increased the fresh yield of sudangrass and ryegrass. The total yield in NPK treatment was the highest among all treatments from 2005 to 2009, and was 17.9%, 17.3%, 21.7%, and 23.2% higher than that of NP treatment, 26.9%, 20.2%, 23.3%, and 25.9% higher than that of NK treatment, and 312.9%, 339.8%, 231.7%, and 223.1% higher than that of PK treatment, respectively. In the rotation, the activities of soil sucrase and urease in NPK treatment were higher than that in CK and PK treatments, while were similar to that of NP and NK treatments. For soil phosphatase, alkaline phosphatase activity was higher than acid phosphatase activity in the rotation, and NP, NK and NPK treatments were lower than CK and PK treatments. 【Conclusion】 The combination of N, P and K fertilizers could increase yield of forage, influence the activities of sucrase, urease and phosphatase in soil and improve soil fertility in the sudangrass and ryegrass rotation system.

Key words: sudangrass and ryegrass rotation, fertilization, yield, sucrase, urease, phosphatase