Dialing in the most corn-profitable and environmentally responsible nitrogen rate

Efficient nitrogen (N) management is essential for optimizing corn (Zea mays L.) productivity while minimizing environmental N losses in subsurface-drained continuous corn (CC) systems. This three-year study (2021 – 2023) at the Southwest Research and Outreach Center (SWROC) in Lamberton, Minnesota evaluated agronomic responses and environmental N losses across five N rates (0 – 360 kg N ha-1) using N best management practices (N-BMPs) including timing (in-season split application), placement (incorporation with tillage of pre-plant fertilizer), and source [enhanced efficiency fertilizers: polymer coated urea (ESN) and urea treated with the urease inhibitor N-(n-Butyl) thiophosphoric triamide (NBPT)]. Measurements included grain yield, plant total N uptake (TNU), soil total inorganic N (TIN) at various depths within the top 90 cm, canopy sensing for N management, and N loss measurements of nitrate (NO3-N) leaching, ammonia (NH3-N) volatilization, and nitrous oxide (N2O-N) emissions. The mean economic optimum N rate (EONR) was 173 kg N ha-1, with a coefficient of variation (CV) of 23%, corresponding to an optimum range of 133 to 213 kg N ha-1. Above this threshold, yield gains plateaued or declined while residual soil N, N2O-N emissions, and NO3-N leaching increased linearly, indicating declining N use efficiency (NUE) and increased environmental risk. At 25% above the mean EONR, total N loss was estimated at 24.6 kg N ha-1, with NO3-N leaching accounting for 86% of the total, compared to only a 3% yield gain. This illustrates the disproportionate rise in environmental loss relative to agronomic benefit. Ammonia volatilization was most prominent in 2021 and influenced primarily by dry surface conditions rather than N rate. Nitrous oxide emissions peaked in 2022, because early-season rainfall events and waterlogging coincided with high surface N accumulation from prior dry conditions. Nitrate leaching dominated in 2023 due to frequent early-season precipitation and drainage. This sequence shows that timing and intensity of precipitation, not only total rainfall, critically shaped dominant N loss pathways. When one loss pathway increased, another often declined, revealing tradeoffs and demonstrating the interconnected nature of N loss mechanisms and the need for integrated management practices. Managing N inputs within a flexible EONR range provides a practical strategy to maintain yield and mitigate environmental losses across variable growing conditions. This study highlights the value of concurrently measuring multiple N loss pathways and supports season-specific adaptive strategies to reduce the environmental footprint of intensive CC production.

Author dc:creator

• Aanerud, Zachary

• Ammonia
• Corn
• Drainage
• Nitrate
• Nitrogen
• Nitrous Oxide

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/11299/278025

OAI identifier oai:identifier

oai:conservancy.umn.edu:11299/278025