Artificial subsurface drainage is essential to sustain crop production in many areas but may also impair water quality by exacerbating nitrate (NO₃)–nitrogen (N) delivery downstream. Cover crops and split‐N application have been promoted as key conservation practices for reducing NO₃–N losses, but few studies have simultaneously assessed their effect on water quality and crop productivity. A field study was conducted to evaluate the effects of N application timing and cover crops on subsurface drainage NO₃–N losses and grain yield in continuous corn (Zea mays L.). Treatments were preplant‐N: 224 kg N ha^–1 split‐applied with 60% fall + 40% preplant in 2018, or as single preplant applications in 2019 and 2020; split‐N: 40% preplant + 60% side‐dress (V6–V7); split‐N + cover crop (CC): Split‐N + cereal rye (Secale cereale L.); and a zero N plot as the control. Across the 3‐yr study period, split‐N + CC significantly reduced flow‐weighted NO₃–N concentration and NO₃–N loss by 35 and 37%, respectively, compared with preplant‐N. However, flow‐weighted NO₃–N concentration (4.3 mg L^–1) and NO₃–N loss (22.4 kg ha^–1) with split‐N were not significantly different from either preplant‐N (4.8 mg L^–1 and 26.4 kg ha^–1, respectively) or split‐N + CC (3.1 mg L^–1 and 16.7 kg ha^–1, respectively). Corn yield was significantly lower in the control treatment but did not differ among N fertilized treatments in any year. These results indicate that combining split‐N application with cover crops holds promise for meeting the statewide interim milestone NO₃–N reduction target of 15% by 2025 without negatively impacting crop productivity.

Nitrogen (N) losses from cropping systems in the U.S. Midwest represent a major environmental and economic concern, negatively impacting water and air quality. While considerable research has investigated processes and controls of N losses in this region, significant knowledge gaps still exist, particularly related to the temporal and spatial variability of crop N uptake and environmental losses at the field-scale. The objectives of this study were (i) to describe the unique application of environmental monitoring and remote sensing technologies to quantify and evaluate relationships between artificial subsurface drainage nitrate (NO₃-N) losses, soil nitrous oxide (N₂O) emissions, soil N concentrations, corn (Zea mays L.) yield, and remote sensing vegetation indices, and (ii) to discuss the benefits and limitations of using recent developments in technology to monitor cropping system N dynamics at field-scale. Preliminary results showed important insights regarding temporal (when N losses primarily occurred) and spatial (measurement footprint) considerations when trying to link N₂O and NO₃-N leaching losses within a single study to assess relationship between crop productivity and environmental N losses. Remote sensing vegetation indices were significantly correlated with N₂O emissions, indicating that new technologies (e.g., unmanned aerial vehicle platform) could represent an integrative tool for linking sustainability outcomes with improved agronomic efficiencies, with lower vegetation index values associated with poor crop performance and higher N₂O emissions. However, the potential for unmanned aerial vehicle to evaluate water quality appears much more limited because NO₃-N losses happened prior to early-season crop growth and image collection. Building on this work, we encourage future research to test the usefulness of remote sensing technologies for monitoring environmental quality, with the goal of providing timely and accurate information to enhance the efficiency and sustainability of food production.

Cereal rye (Secale cereale L.; CR) is promoted as a cover crop as a practice for reducing nitrate leaching losses in the U.S. Midwest. However, early‐season nitrogen immobilization during CR decomposition may contribute to yield reductions in corn (Zea mays L.). Field trials were conducted at three sites to determine if N as a starter fertilizer could increase the plant N uptake and grain yield of corn following CR. Treatments were a two‐way factorial with two cover crop treatments (CR and no CR) and four fertilizer treatments: subsurface banded (2 by 2 inches) at planting as urea ammonium nitrate (UAN) at 0, 25, 50, and 75 lb acre^–1. Treatments received the same total N within sites, with the remainder injected between rows at side‐dressing as UAN. Nitrogen uptake and yield were unaffected by the starter N × CR interaction in all sites. At one of the sites, CR significantly reduced N uptake and corn yield at the R6 stage by 16 and 4.5% relative to no CR, respectively. Corn yield was unaffected by starter N at two sites, whereas applying 50 or 75 N lb acre^–1 increased yields compared with 0 and 25 N lb acre^–1 at the third site. These findings suggest that starter N could increase early‐season N uptake but had an inconsistent impact on corn yields. Therefore, further investigations under different soil N conditions are needed to provide insights into how starter N rates can be adjusted to optimize corn yields within a CR system.

Biochar is promoted as a means of improving soil fertility. Yet, few experiments have investigated its potential to improve nitrogen (N) use efficiency for high‐yielding maize production in the U.S. Midwest. We tested the hypothesis that biochar application increases inorganic soil N availability during maize growth, leading to higher grain yields and N recovery efficiency while reducing the risk of N leaching following harvest. Four N fertilizer rates (0, 90, 179, and 269 kg ha⁻¹ as urea ammonium nitrate [UAN] solution) were applied with or without biochar (10 Mg ha⁻¹) before planting in a two‐year field study. Inorganic soil N concentration was measured during the growing season (0–15 cm), and deep soil cores were obtained following harvest (0–90 cm). Results show that biochar did not affect maize yield, crop N uptake, or N recovery efficiency (by the difference method) across N rates, and there was no biochar by N rate interaction. While biochar lowered soil inorganic N concentrations on several sampling dates, this did not translate into seasonal differences in cumulative soil N availability, although grain yields in the unfertilized control were ~10% lower with biochar, suggesting net N immobilization. Biochar partially reduced the risk of N leaching following harvest by decreasing soil N concentrations at 30–60 cm, but mean concentrations for 0–90 cm were not different. Compared to previous work highlighting the benefits of biochar in arid climates with low soil fertility, we found no evidence of increased crop yield, NRE, or reduced risk of N leaching on Mollisols in a temperate climate.

Few studies have addressed whether in‐field practices to reduce nitrate‐nitrogen (NO₃‐N) leaching might increase nitrous oxide (N₂O) emissions, which could undermine attempts to mitigate agricultural N pollution. Over a 3‐year period, we assessed the impacts of N application timing and cereal rye (Secale cereale L.) cover crop on subsurface drainage NO₃‐N leaching and N₂O emissions to quantify changes in total N loss and corresponding social and environmental damage costs under continuous corn (Zea mays L.). While NO₃‐N losses were reduced by 37% with the combination of in‐season split N application and cereal rye cover crop relative to pre‐season N application, soil N₂O emissions increased by 26%, highlighting a tradeoff between N loss pathways. As a result, total N losses and social and environmental damage costs from each system were not different. These results demonstrate the importance of addressing agricultural N pollution using a holistic framework accounting for the environmental and social risks of both NO₃‐N losses and N₂O emissions.

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.