Effect of controlled-release nitrogen fertilizer on growth and fertilizer nitrogen use efficiency of double rice in southern China

Controlled-release nitrogen fertilizer("Meister"made by Japan) were chosen with two application rates,N 75 and 150 kg/ha,to investigate the nitrogen release dynamics of controlled-release fertilizer and its effects on growth, yield,and nitrogen use efficiency of early rice and late rice in red soil paddy field of Qiyang,Hunan province of Southern China.The results showed that the nitrogen release dynamics of S_9 and LP_(70)(40%)+LPS_(100)(60%) met with uptake by early rice,and late rice satisfactorily.Furthermore,a significant positive correlation was observed between the accumulate N uptake by early rice and N release from S_9(R~2=0.9764),and the accumulate N uptake by late rice and N release from LP_(70)(40%)+LPS_(100)(60%)(R~2=0.9968).Compare to the same application rate of urea,applying controlled-release N fertilizer N 75 kg/ha increased the grain yield by 3.6%and 9.3%,and nitrogen use efficiency by 29.9 percent point and 10.4 percent point for early rice and late rice,respectively.Controlled-release nitrogen fertilizer could give more effective panicles and tillers than those of urea.No significant difference was observed in grain yield between N 150 kg/ha of urea and N 75 kg/ha of controlled-release nitrogen fertilizer.Thus,application controlled release nitrogen fertilizer N 75 kg/ha was recommended as best fertilization approach with comprehensive consideration on high yield and high efficiency.