Integrated Nitrogen and Sulfur Management to Improve Nitrogen Use Efficiency and Reduce Nitrogen Losses in Winter Wheat Systems

Commodities

Practices

Integrated Nitrogen and Sulfur Management to Improve Nitrogen Use Efficiency and Reduce Nitrogen Losses in Winter Wheat Systems

Nitrogen losses during the non-growing season represent a persistent environmental and economic challenge in southern Illinois, where poorly drained and tile-drained soils dominate corn-soybean and winter wheat production systems. Despite widespread interest, growers lack locally validated guidance on nitrification inhibitors, split nitrogen applications, and sulfur co-fertilization under variable field conditions. This knowledge gap leaves producers navigating costly nutrient management decisions without adequate research-based support, an issue this project addresses.

Building on a field experiment initiated in 2025 at the Southern Illinois University Belleville Research Center (BRC), this project evaluates which combinations of nitrification inhibitor (NI) rates (label-recommended, 0.5×, and 2×), application timings (fall + spring green-up + jointing; fall + spring green-up; or spring green-up only), and sulfur co-application affect soil nitrogen dynamics, grain yield, protein content, nitrogen use efficiency (NUE), and nitrate loss risk in winter wheat. Specific questions include: (1) Does shifting nitrogen through ammonium-based P fertilizers to spring reduce nitrate loss? (2) How do NI rates affect soil nitrogen dynamics and grain quality under varying environmental conditions? (3) Do split applications provide measurable agronomic and environmental advantages over a single spring application with inhibitors and at which rate? (4) How does sulfur co-application influence NUE? (5) Do the economic returns justify adoption?

The study uses a split-plot design with four replications and will expand to two additional sites (1) the Agronomy Research Center (naturally drained soil) and (2) a cooperating farmer field (tile-drained soil), capturing variability across soil drainage classes representative of lower Midwest production agriculture. Measurements include soil nitrate dynamics, grain yield and protein, plant tissue nutrient analysis, nitrate leaching, and economic return on investment, providing an integrated agronomic and environmental assessment. Outreach will target wheat growers, crop advisors, and extension experts who will translate findings into practice. Results will be shared through a fact sheet, on farm peer-to-peer trials, regional workshops, and presentations at the BRC Field Day, which draws approximately 200 participants annually. We anticipate at least 30% of participating growers will improve understanding of nitrogen-sulfur interactions and 10-15% will adopt or express intent to adopt improved management practices. Ultimately, this project helps Midwest producers reduce fertilizer's environmental footprint, protect soil and water quality, and improve the economic sustainability of winter wheat production, directly advancing NC SARE's mission of a more productive, sustainable agriculture.

The primary audience includes winter wheat producers, crop advisors, and extension personnel in Illinois and the North Central region. Field demonstrations, on-farm trials, and producer meetings will generate measurable learning and action outcomes related to improved N and S management.

Learning Outcomes: We anticipate at least 30% of participants will demonstrate improved understanding of N loss pathways during the non-growing season, specifically how leaching through tile-drained soils and denitrification in poorly drained soils create environmental risks, and how application timing, nitrification inhibitors, and S co-application can reduce those risks. At least 20% will improve their ability to evaluate economic returns using return-on-investment comparisons. Outcomes will be assessed through pre- and post-event surveys measuring changes in knowledge and attitudes toward nutrient management.

Action Outcomes: At least 15% of producers will express intent to adopt or modify at least one practice, such as shifting to spring-only N timing, adjusting NI rates, or incorporating S alongside N fertilizers, as measured by post-event surveys at field days, and the NUE conference. Among these, at least 50% will report implementing one or more practices within one to two growing seasons through follow-up surveys. On-farm trials are expected to support higher adoption through peer-to-peer interaction with farm advisors and extension educators.

By increasing producer knowledge of N-S interactions and supporting measurable practice change, this project will help farmers improve N use efficiency, reduce input costs and ecological challenges, contributing to sustainable and economically resilient winter wheat production across the North Central region.