Study on Soybean Optimum Fertilizing Rate in Drought Year in North Black Soil District of China

The experiment adopts different ratios of N,P and K fertilizer,and the relationships among the ratio of fertilizer,soybean yield,use ratio of fertilizer and economic benefit are studied in north black soil district of China in drought year.The testing results show:when P and K fertilizer is sufficient,soybean yield is the highest under the N fertilizer application at N 75 kg/hm2,;when N and K fertilizer is sufficient,soybean yield is the highest under the P fertilizer application at P2O5 90 kg/hm2,when N and P fertilizer is sufficient,soybean yield is the highest under K fertilizer application at K2O 48 kg/hm2.The results of regression analysis show that the optimum applied amount of fertilizer is N 78.3 kg/hm2 and P2O5 83.3 kg/hm2 in order to gain the highest yield.By calculating the use ratio of fertilizer and economic benefit,the best applied amount of fertilizer is N 75 kg/hm2,P2O5 90 kg/hm2,K2O 48 kg/hm2 in order to obtaining the highest economic benefit.And the optimum relatively economic ratio of fertilizer is N 45 kg/hm2,P2O5 60 kg/hm2,K2O 48 kg/hm2.Finally,according to the climate factors,the optimum applied amount of fertilizer is N 60 kg/hm2,P2O5 75 kg/hm2,K2O 48 kg/hm2 and the optimum ratio of N∶P2O5∶K2O is 1.25∶1.56:1.