Effects of Reducing N Application on Crop N Uptake,Utilization and Soil N Balance under Rice-wheat Rotation System on Middle and Lower Reaches of Yangtze River Region

In this trial,the effects of the reduction of nitrogen fertilizer application on the nitrogen absorption and utilization of crops and soil N balance were studied with the continuous two cycles of rice-wheat rotation.The results showed that based on traditional fertilizer recommendation(N 195 kg/hm2 in wheat,210 kg/hm2 in rice,according to the effects of base fertilizer,tiller fertilizer and jointing fertilizer of 40 %,30 %,30 % three times applying),and nitrogen amount were reduced by 20 %,combined with integrated control measures,the yield was not reduced,but apparent recovery rate,agronomic efficiency,nitrogen partial factor productivity and contribution rate were enhanced.The nitrogen accumulation in crops increased with the increase of nitrogen fertilizer application volume,also the same as the residue of soil inorganic nitrogen and nitrogen apparent losses.The nitrogen requirement amount of wheat was higher than that of rice for producing the same quantity of grain yield,but in the apparent loss of nitrogen,the rice was higher than wheat.