Wheat fields lose far more nitrogen in wet years
Shelar VB, Prasad R, Ortiz BV, Batchelor W, Arnall B
Soil Health
The runoff feeding algae blooms in nearby rivers and lakes often traces back to exactly this kind of field-level nitrogen leaching, which this study shows swings dramatically with rainfall and soil drainage even within a single farm.
Researchers tracked what happens to nitrogen fertilizer in a wheat field over decades of weather, splitting the field into a high-yield zone and a low-yield zone to see if location mattered. They found that almost all the lost nitrogen washes down through the soil as nitrate rather than escaping as gas, and the higher-yielding part of the field lost more nitrogen because its soil drains faster and started with more nitrogen already in it. Wet years made things much worse, nearly 50% more nitrogen lost compared to drought years, showing that farmers may need to adjust fertilizer plans based on both soil type and the season's rainfall outlook.
Key Findings
Nitrate leaching accounted for 94-98% of total nitrogen losses across both growing seasons, dwarfing volatilization (1-2 kg N/ha) and denitrification (0.4-1.0 kg N/ha)
The high-yielding zone lost more nitrogen to leaching (39-98 kg N/ha) than the low-yielding zone (69-70 kg N/ha), due to faster soil drainage and higher starting soil nitrogen, not differences in crop uptake
Across 32 years of simulation, average leaching rose from 65 ± 12 kg N/ha in drought years to 96 ± 21 kg N/ha in wet years, while volatilization losses increased during drought
chevron_right Technical Summary
A study of a wheat field in the Southeastern U.S. found that nitrogen fertilizer washes away as nitrate mostly through leaching, and the amount lost depends heavily on how wet the year is and which part of the field you're in, with wetter years and higher-yielding zones losing far more nitrogen to groundwater.
Abstract Preview
Original paper
Environmental nitrogen losses in winter wheat across yield zones under long-term precipitation variability.
Nitrogen (N) loss dynamics from winter wheat in humid agroecosystems remain uncertain due to variability in soil characteristics across yield zones and high interannual precipitation variability. W...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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