Relationship of in‐season soil nitrogen concentration with corn yield and potential nitrogen losses

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, NH4‐N + NO3‐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.

Does biochar improve nitrogen use efficiency in maize?

“…Given the high indigenous soil N supply, even if small changes in cumulative soil N availability due to biochar were detected, this likely would not have caused nutrient deficiency. Previous work in Illinois has shown that lower soil N concentrations at key maize growth stages are associated with yield reductions, but the relative differences were much larger than observed in the current study (Preza Fontes et al., 2020). Thus, the lack of effects of biochar on maize yield and N uptake was not unexpected.…”

A 3-year field study to assess winter cover crops as nitrogen sources for an organic maize crop in Mediterranean Portugal

“…Kramberger et al (2014) reported the association between high soil N balance values, low maize yields and low N uptake values in maize. In this study, the opposite was true, because it was in the treatments where the highest yields were obtained that we had the highest accumulated N values, the highest values in the soil N balance and also the highest % CNc supplied to the main crop, like in a study developed by (Preza-Fontes et al, 2020). These results evidence the positive effects of cover crops in supply N to succeeding crop.…”

Development of an Online Tool for Tracking Soil Nitrogen to Improve the Environmental Performance of Maize Production

“…The methods for conducting field experiments to monitor SMN over time have been previously reported by Banger et al [20] and Preza-Fontes et al [21]. Briefly, the database of SMN concentrations contained a total of 1149 observations collected from 32 site-years of N management studies conducted at research stations and on-farm trials across Illinois between 2015 and 2018 (Table A1 in Appendix A).…”

“…Soil N concentrations were averaged across depths, resulting in SMN (sum of nitrate-N and ammonium-N) at 0-60 cm depth. The N management treatments consisted of 12 different combinations of N fertilizer rates, timing, and source, plus a control treatment with zero N (see Preza-Fontes et al [21] for a full description of N treatments). In addition to these treatments, the multiple locations across years created a range of SMN concentrations under different soil and weather conditions.…”

“…The increasingly common occurrence of wet early-spring weather can contribute to uncertainty about soil N status, which in turn, increases the tendency for farmers to apply additional N. Previous studies have shown that early-season SMN is positively correlated with corn yield [13,28,29], suggesting that low SMN is associated with a risk of a yield penalty. In contrast, applying N above the recommended rates to maximize crop productivity can increase N losses and economic costs [21]. While there is a delicate balance between profitability and environmental N losses, a recent survey study in Illinois found that most of the participants (farmers) were concerned about the economics and environmental impacts of nutrient loss, with some participants reporting making changes in their production practices to minimize nutrient losses in their fields [30].…”