What question did this study set out to answer?

This research aims to evaluate how late-season nitrogen applications affect ammonia volatilization and crop response in corn.

April 22, 2026Open Access

Ammonia volatilization from late-season nitrogen applications in corn: Effects of timing, source and placement

Key Points

This research aims to evaluate how late-season nitrogen applications affect ammonia volatilization and crop response in corn.
Conducted a 15-site field study across Illinois, Indiana, and Ontario from 2021 to 2023.
Applied various nitrogen sources (urea, UAN) at different timings (V5, V13) and placements (injected, surface) with and without urease inhibitors.
Measured ammonia volatilization and related it to soil properties like cation-exchange capacity and rainfall.
Injection of UAN led to the lowest nitrogen losses (approximately 3 kg N ha⁻¹) across all treatments.
Urease inhibitors decreased ammonia volatilization by 65% for urea and 36% for UAN.
Ammonia losses were greater for urea at the V5 stage compared to V13, while UAN losses remained stable regardless of timing.

Abstract

In-season nitrogen (N) applications in corn ( Zea mays L.) can improve fertilizer N use efficiency. However late-season applications after canopy closure may increase ammonia (NH₃) volatilization, reducing soil N availability and contributing indirectly to greenhouse gas emissions. We quantified ammonia (NH 3 ) volatilization and crop response to fertilizer N source, placement, rate and timing treatments across 15 environments in Illinois, Indiana and Ontario (2021–2023). Treatments consisted of urea and urea-ammonium-nitrate (UAN) injected below the soil and surface-placed with or without a urease inhibitor (UI). Canadian and U.S. sites both applied 146 kg N ha −1 at V13 with U.S. sites also applying at V5. Additionally, U.S. applied 56 kg N ha −1 at both V5 and V13 growth stages. Injection of UAN produced the lowest losses (∼3 kg N ha −1 ) regardless of N source, while UIs reduced volatilization by 65% and 36% for urea and UAN, respectively. Without UIs, surface-applied UAN emitted 35 kg N ha⁻¹ less than urea. N timing only influenced volatilization from urea and was reduced at V5. Cation-exchange capacity (CEC) and post-application rainfall most strongly predicted volatilization. Volatilization declined as CEC and rainfall (events ≥ 30 mm) increased, although high-CEC soils needed more rainfall for equivalent suppression. Positive grain yield and N uptake response to UIs or injection only occurred when corn N demand exceeded the applied N rate, and volatilization loss potential was > 46 kg N ha⁻¹ . Otherwise, agronomic benefits were negligible. These findings can refine environmental models and guide late-season N management under diverse pedo-climatic conditions. • 15-site field study quantified NH 3 loss from late-season (V13) N in maize (2021–23) • Urease inhibitors lowered NH 3 loss by 65% (urea) and 36% (UAN) • NH 3 loss greater for urea at V5 than V13; UAN NH 3 loss unaffected by timing • Rainfall events ≥ 30 mm suppressed NH 3 loss but more rain needed when CEC > 23 • Time to first rain, number of rain events > 30 mm and CEC explained 40% of NH 3 variation

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Kang et al. (Mon,) studied this question.

synapsesocial.com/papers/69e8656e6e0dea528dde9fd4 https://doi.org/https://doi.org/10.1016/j.agee.2026.110432

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