Study on the Effect of Rice Straw Return to Field and Nitrogen Fertilizer Combined Application in Cold Region

In huge area contrast experiment,the effect of rice straw treaded by different methods return to field on the growth and yield of rice and soil fertility was studied.The results showed that rice straw return to field could increase yield of rice among all treatments, the yield increments ranged between 2.7% and 10.6% . The optimum formulation with the highest yield was rice straw 500kg/667m2+14 kg/667m2 ammonium bicarbonate+20kg calcium carbonate per mu, the yield attained 553.4 kg/667m2, and increased 10.6% than the control, the second was 250kg/667m2+14 kg ammonium bicarbonate per mu, its yield was 547.8 kg, and increased 9.5% than the control, The optimum formulation with the lowest yield was rice straw500kg/667m2+6 kg/667m2ammonium bicarbonate, the increasing rate of output was 2.7%. Plant height of every treatment was similar during the same period. The resistance of treatment four on rice blast, rice brown spot and bowning ear of grain was improved obviously, the incidence rate of rice blast decreased by 20%, the ability of resistant to lodging and premature senescence was improved significantly. With the increase of crop-residue incorporation, grain number per spike and the shriveled seed percentage presented an increasing trend, but thousand kernel weight had a descreasing trend. And significant positive correlation was observed between the application rate of ammonium bicarbonate and yield of rice, the correlation coefficient was 1.The yield of rice treated by treatment four increased 18.3kg than that of treatment three, and the increasing rate of yield was 3.4%.