Abstract:

Effects of continuous applying controlled release nitrogen fertilizer under double rice cropping system were studied by modeling 3 types of paddy soils in Dong-Ting Lake area using micro-plot trials conducted from 2005 to 2008. Four treatments as no fertilizer (CK), urea, controlled release nitrogen fertilizer (CRNF) and 70% controlled release nitrogen fertilizer (70% CRNF) were designed. The results showed that the yield in treatments with controlled release nitrogen fertilizer (CRNF) at N 150 kg/hm2 were increased by 10.3%, 8.0% and 2.4% compared with CF treatment, in alluvial loamy paddy soil (ALS), purple calcareous clayed paddy soil (PCS), and reddish yellow clayed paddy soil (RYS), respectively, and the yield in treatments with 70% CRNF were increased by 6.1%, 2.6% and -0.8%, respectively. The ranking order of nitrogen uptake amount by plant in early rice and late rice were CRNF >70% CRNF >Urea >CK in all 3 types of soils. Nitrogen utilization efficiency of CRNF in above 3 types of soils were 60.7%, 59.6% and 56.3%, increased by 23.8%, 19.4% and 16.3% compared with CF, respectively. Fertilizer use efficiency of CRNF in early rice were higher than of 70% CRNF during the whole experiment stage, while it in late rice turned from increase to decrease at the 3rd year. Continuous application of controlled-release nitrogen fertilizer could alleviate decreasing rate of soil nitrogen fertility and organic carbon, especially in alluvial loamy paddy soil. The results indicated that application controlled release nitrogen fertilizer could promote soil fertility, increase rice yield and fertilizer-N use efficiency in double-rice cropping system.