Abstract

Info

Title:: Response of the Ability of N₂ Fixation and Yield to Nitrogen Application Rate in Soybean

Author(s):: -; ?(Key Laboratory of Mollisols Agroecology，Northeast Institute of Geography and Agroecology，Chinese Academy of Sciences，Harbin 150081，China)

Abstract:: ?In order to quantify the relationship between the nitrogen application rate and the ability of nitrogen fixation，and find the critical threshold of nitrogen application rate at different growth stage which could improve soybean yield and had no adverse effect on N₂ fixation ability.Pot experiment were conducted taking Heinong 35 as test material，total fertilizer N were applied at vegetative stage(V2)，early bloom(R1)，early pod(R3)and grain fill(R5)，respectively，with five application rates(0，75 150，225，300 and 375 kg·ha^-1),and the nodule number，biomass,nitrogenase activity and yield were determined.Nitrogen applied at different growth stage remarkably decreased nodule number，biomass and nitrogenase activity at R6 with an order of V2＞R5＞R3＞R1.There were significantly negative linear correlations between nodule number，biomass and nitrogenase activity and the nitrogen application rate.Moreover，the trends of dry matter accumulation and yield were expressed as an order of R1＞R3＞V2＞R5，among which nitrogen applied at V2，R1and R3 had significant promoting effect.At each stage,the nitrogen application rate of 225 kg·ha^-1 had the highest dry matter accumulation and yield.There was different threshold of nitrogen application rate at different growth stage,and R1 was the crucial stage to determine the ability of nitrogen fixation and yield.