Greenhouse gas fluxes in an eastern corn belt soil: Weather, Nitrogen source, and rotation

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Relative contributions of diverse, managed ecosystems to greenhouse gases are not completely documented. This study was conducted to estimate soil surface fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) as affected by management practices and weather. Gas fluxes were measured by vented, static chambers in Drummer and Raub soil series during two growing seasons. Treatments evaluated were corn cropped continuously (CC) or in rotation with soybean (CS) and fertilized with in-season urea-ammonium nitrate (UAN) or liquid swine manure applied in the spring (SM) or fall (FM). Soybean (SC) rotated with CS and restored prairie grass (PG) were also included. The CO2 fluxes correlated (P ≤ 0.001) with soil temperature ({rho}: 0.74) and accumulated rainfall 120 h before sampling ({rho}: 0.53); N2O fluxes correlated with soil temperature ({rho}: 0.34). Seasonal CO2–C emissions were not different across treatments (4.4 Mg ha–1 yr–1) but differed between years. Manured soils were net seasonal CH4–C emitters (0.159–0.329 kg ha–1 yr–1), whereas CSUAN and CCUAN exhibited CH4–C uptake (–0.128 and –0.177 kg ha–1 yr–1, respectively). Treatments significantly influenced seasonal N2O–N emissions (P < 0.001) and ranged from <1.0 kg ha–1 yr–1 in PG and SC to between 3 and 5 kg ha–1 yr–1 in CCFM and CSUAN and >8 kg ha–1 yr–1 in CCSM; differences were driven by pulse emissions after N fertilization in concurrence with major rainfall events. These results suggest fall manure application, corn–soybean rotation, and restoration of prairies may diminish N2O emissions and hence contribute to global warming mitigation.

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