The experiment was conducted in Renshou County (29°60' N, 104°00' E), Sichuan Province, China. The field climate was subtropical monsoon humid, with average annual temperature of 17.4°C, rainfall of 1009.4 mm, and sunshine of 1196.6 hours. Fig 1 shows the temperature, daylight hours, precipitation and evapotranspiration for the cropping seasons. Total N, total P, total K, alkali hydrolysable N, Olsen-P and exchangeable K in the top 20 cm of soil of the experimental site were 0.90 g kg-1, 0.50 g kg-1, 14.28 g kg-1, 77.35 mg kg-1, 22.83 mg kg-1, and 196.63 mg kg-1, respectively.