Nitrogen fertilizer application to soybean [Glycine max (L.) Merr.] in Iowa, USA, has shown inconsistent results. We performed a study in central Iowa (2015 and 2016) to investigate the effect of N fertilizer rate (0, 45, 90, 135 kg N ha−1) and application timing (planting, flowering, pod setting) on soybean yield, yield components, and to calculate the economic net return to N fertilizer. Results showed a positive effect of N fertilizer on soybean yield and yield components both years. Seed and aboveground biomass dry weight were positively correlated to N fertilizer, and both were 17% greater than No-N treatment. Nitrogen fertilizer rate that significantly increased seed and aboveground biomass was 135 kg N ha−1 regardless of application timing (2015), or at planting (2016). Moreover, the same N fertilizer addition applied at planting benefitted seed and aboveground biomass N accumulation only in 2016 (avg. 32.00 and 34.68 g N uptake m−2, respectively), both 1.5-times higher than No-N treatment. Favorable environmental conditions during 2016 lead to hand-measured yield difference of 22% compared to 2015. Economic net return analysis showed that the additional revenue from increased yield attributed to supplemental N fertilization offset the application cost, resulting in net return gains between US5.83to281.89 ha−1 (all treatments except 45 kg N ha−1 on 2015). This study highlights the importance to parse out soybean yield in its components, and the need to quantify yield gains from N fertilizer additions in economic terms which shed some light on any tradeoffs.This article is published as Córdova, S. Carolina, Sotirios V. Archontoulis, and Mark A. Licht. "Soybean profitability and yield component response to nitrogen fertilizer in Iowa." Agrosystems, Geosciences & Environment 3, no. 1 (2020): e20092. doi:10.1002/agg2.20092. Posted with permission.
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made
