Nitrous oxide emissions from manured, no-till corn systems
2021
Ponce de León, María A. | Dell, Curtis J. | Karsten, Heather D.
Using dairy manure and legumes in crop rotations can reduce inorganic N inputs for corn (Zea mays L.), yet these practices can also contribute to nitrous oxide (N₂O) emissions. In two crop rotations we investigated how different (i) organic and inorganic N amendments and (ii) prior legume crops with broadcast manure influenced direct N₂O emissions from silt-loam soils planted to no-till corn. We measured N₂O fluxes from April to December for two years using closed vented chambers from soils planted to corn with no spring residue to compare inorganic N fertilizer (S-UAN) and two liquid dairy manure application methods: surface broadcasted (S-BM) and injected (S-IM). Emissions were also measured to compare the effect of crop residue of perennial forages, a green manure legume, or soybean (Glycine max L. Merr.) from soils all amended with liquid dairy manure. Nitrous oxide emissions were greatest during the 15–45 days after manure was injected compared to broadcasting, and cumulative N₂O emissions were larger from S-IM (2.8–2.5 kg ha⁻¹) than S-BM (1.4–0.7 kg ha⁻¹) and S-UAN (0.3 kg ha⁻¹). Cumulative and yield-scaled N₂O emissions did not differ among the prior legume treatments. A ranking approach based on random forests, identified the most important variable contributing to N₂O emissions in both comparisons as corn growing degree days, indicative of the asynchrony of spring legume termination and manure application with corn planting and N use; and changing environmental conditions for N mineralization and denitrification.
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