Soybean Yield, Nutrient Uptake, and Role of Biological Nitrogen Fixation

Few investigations are available looking at the changes over time in nutrient uptake and yield, in addition to the study of nutrient stoichiometry as a metric of nutrient limitations in soybean. The presentation will be focused on: 1) understanding the historical changes on yield, total biomass, and nutrient (N, P, K) content and concentration in studies published from 1921 to 2016; 2) investigating the role of biological nitrogen fixation (BNF) as a main contributor of this nutrient to the plant; and 3) exploring the effect of management practices for closing yield gaps. Historical seed yield increase was primarily driven by increase in biomass rather than harvest index (HI) with also increasing NHI. Overall, contribution of BNF to plant N demand was 56%, representing a total contribution of 122 lbs N per acre. From a pragmatic viewpoint, the use of the best management practices (BMPs) impacted soybean yield, biomass and N uptake. Narrow row spacing, high seeding rate, and balanced nutrition increased partitioning efficiency for biomass and nitrogen, and consequently increased final yields. These findings have implications for soybean production and integrated nutrient management to improve yield, nutrient use efficiency, and seed nutrient composition.