Compaction and Tillage Effects on Nitrous Oxide Emission from Winter Oat-Corn-Soybean Rotation in Ohio.

Nitrous oxide (N₂O) produced by anthropogenic activities have been linked to the observed and predicted warming trends in global climate. Land management practices, soil properties and climatic factors are major regulators of nitrous oxide emissions from farmland. The study was conducted to investigate the effects of compaction and tillage management on N₂O emission in winter oat-corn-soybean rotation on Crosby silt-loam soil in southern Ohio. Three levels of compaction — 0, 10 and 20 ton were superimposed on no-till and conventional till management in alternating years in fall after harvest. Polyvinyl chloride chambers (15 cm diameter) were installed in each plot in between plant rows. Vented chamber lids, fitted with sampling port were used to close the chambers during sampling and soil air samples were obtained at 0, 30 and 60 minutes and analyzed for N₂O concentration by gas chromatography. Fluxes of N₂O were measured at 2 weeks intervals for two years. In addition, soil moisture, soil temperature, NO₃^- and NH₄⁺ concentration of the top 10 cm were determined for each sampling date. Daily N₂O fluxes ranged from 0.37 to 15 mg N m^-2 d^-1. Significantly higher fluxes were observed in spring (March-June) compared to other seasons of the year. Fluxes from corn were generally higher than those from winter oats and soybean in both years. Greater N₂O fluxes were recorded from the compacted plots especially during periods of high soil moisture contents. The N₂O fluxes were positively correlated with soil temperature, NO₃^--N and NH₄⁺-N concentrations. These findings suggest that use of heavy farm implements may have impact on N₂O emissions from farmland.