Relationship of in‐season soil nitrogen concentration with corn yield and potential nitrogen losses
Giovani Preza Fontes, Emerson D. Nafziger, Laura E. Christianson, Cameron M. Pittelkow
Abstract
Abstract New process‐based tools for predicting in‐season soil nitrogen (N) levels has the potential to provide timely information for N management decisions for corn ( Zea mays L.) production systems in the U.S. There is, however, little published data supporting the assumption that soil mineral N (SMN, NH 4 ‐N + NO 3 ‐N at 0–60 cm) is correlated with yield response at different vegetative growth stages. Moreover, the degree to which changes in SMN influence the risk of N losses is uncertain. Data from 32 site‐years of field experiments in Illinois (2015–2018)—that included 12 combinations of N fertilizer rate, timing, and source—were used to evaluate the relationship between SMN concentration and grain yields across vegetative growth stages and estimate the exceedance probability of N losses. Overall, SMN across vegetative growth explained 46–61% of the variation in grain yield. Critical level of SMN that optimized yield decreased from 23.4 mg kg −1 at V5‐V7 to 9.1 mg kg −1 at VT‐R1 growth stage, but it was consistent, ranging from 14.7 to 16.3 mg kg −1 , among sampling periods between V8 and V16 stages. While increasing SMN from deficiency (below critical levels) to sufficiency (at critical levels) increased yields by 22% (11.8 vs. 14.4 Mg ha −1 ), it also increased the probability of environmental N losses throughout vegetative growth, indicating a clear tradeoff between production and sustainability goals. These results help guide the development of sustainable in‐season N management strategies by illustrating the importance of incorporating risks of environmental N losses when trying to reach optimum grain yield levels.