Abstract: Reduced fertilization experiments of maize and soybean were conducted in Xunke,Aihui,beian,Hailun and Bayan in Heilongjiang Province in order to determine the productivity of arable black soil,fertilization status and fertilizer use efficiency.The result showed that soybean yield with no fertilizer treatments (CK) changed from 1 370 kg·hm^-2~3 586 kg·hm^-2 with the coefficient of variation of 35% in all experimental sites with exception of Bayan in 2014 and 2015.Soybean yield in 2014 was increased by 2~45% in fertilizer application treatments compared with CK,significant increase in soybean yield was only observed in Aihui.In 2015,soybean yield in fertilization treatments (NPK,N₂PK and N₂P₂K) was significantly increased in Aihui,Xunke and Beian compared with CK,but additional N and P fertilizer application (N₂PK and N₂P₂K) also increased soybean yield and economic benefit compared with NPK (p>0.05).Fertilizer use efficiencies of soybean were a little bit low with 13.7%~20.9%,5.1%~10.5% and 8.0%~20.4% for N,P and K fertilizer use efficiency,respectively.Economic benefit of N fertilizer was more than that of P and K fertilizers,the highest economic benefit of soybean was found in N₂PK treatment (N 61.5 kg·hm^-2,P₂O₅ 69 kg·hm^-2,K₂O 46 kg·hm^-2).Maize yield in fertilization treatments was increased by 32%~148% compared with CK,there was no significant difference among different fertilization treatments,additional N and P fertilizer application treatments (N₂PK and N₂P₂K) had no effects in increasing maize yield compared with NPK.The economic benefit of P fertilizer was more than that in N and K fertilizers for maize.Therefore,amount of fertilizer application of soybean and maize could be decreased by 25% and 30%,respectively,with reduction in P and K fertilizer for soybean,N and K fertilizer for maize.The recommended fertilizer application rate in the northern part of Mollisols region was N 60 kg·hm^-2,P₂O₅ 70 kg·hm^-2,K₂O 40 kg·hm^-2 for soybean,N 150 kg·hm^-2,P₂O₅ 60 kg·hm^-2,K₂O 40 kg·hm^-2 for maize.