Effects of straw incorporation plus nitrogen fertilizer on rice yield, nitrogen use efficiency and nitrogen loss

【Objectives】 Exploration of the theory and technology of N application along with total straw incorporation has great significance for raising rice yield and N use efficiency, alleviating nitrogen pollution in rice production in China.【Methods】 A split plot field experiment was conducted using monolith lysimeter with a local rice Nanjing 46 as material in Changshu Agro-ecological Experimental Station, Jiangsu Province, China from 2009 to 2011. The main plot was total wheat straw incorporation (S) and no straw incorporation (S0); the sub-plots were four N rates: 120 kg/hm2 (N1), 180 kg/hm2 (N2), 240 kg/hm2 (N3) and 300 kg/hm2 (N4), with no N application as control (CK). The amount of ammonia volatilization, total N contents in leachate and soil, the N contents in straw in different growth periods and grains were determined, the rice yields were investigated.【Results】 The rice yield was increased with the increasing of N application rate. Compared with no straw incorporation treatments, the average rice yields of S+N treatments were increased by 6.3%, and the highest yield was obtained in SN3 treatment. N use efficiencies were declined with the increasing of N rates in rice reason, which could be enhanced by straw incorporation. Agronomic N efficiency and N apparent recovery in S+N treatments were all higher than those of N treatments by 1.4-3.4 kg/kg and 1.8%-4.2% respectively. With the increasing of N application rate, the amount of N residual, ammonia volatilization and N leaching in paddy field increased. Compared with no straw incorporation, the amount of ammonia volatilization and N residual in paddy field with straw incorporation was increased by 18.2% and 10.1 kg/hm2 respectively at N application rate of 240 kg/hm2, and the N leaching and total N loss were reduced by 30.9% and 6.0% respectively.【Conclusions】 Under the straw completely incorporation, optimum N application rate could increase the N efficiency and rice yield, reduce the total N loss. In this research, the wheat straw incorporation with N application of 240 kg/hm2 is the optimal mode.