Cover cropping affects soil N₂O and CO₂ emissions differently depending on type of irrigation

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• 作者：Cynthia M. Kallenbach ; Dennis E. Rolston ; William R. Horwath
• 关键词：N₂O ; CO₂ ; Greenhouse gas ; Irrigation management ; Cover crop ; Tomato ; Nitrogen fertilizer management
• 刊名：Agriculture, Ecosystems & Environment
• 出版年：2010
• 出版时间：15 May 2010
• 年：2010
• 卷：137
• 期：3-4
• 页码：251-260
• 全文大小：849 K

文摘

Agricultural management practices such as subsurface drip irrigation (SDI) and winter legume cover cropping (WLCC) influence soil water dynamics as well as carbon and nitrogen cycling, potentially changing emission rates of soil CO₂ and N₂O, principal greenhouse gases. A split plot tomato field trial in California's Central Valley was used to evaluate the use of SDI and WLCC on event-based CO₂ and N₂O emissions. SDI and WLCC were compared to the region's more conventional practices: furrow irrigation (FI) and no cover crop (NCC). Our results indicate that SDI offers the potential to manage cover crops without the significant increases in greenhouse gas production during the growing season as seen under FI cover-cropped systems. The highest N₂O emissions occurred during the beginning of the rainy season in November in the FI–WLCC treatment (5 mg m⁻² h⁻¹) and the lowest in August in the SDI–NCC treatments (4.87 μg m⁻² h⁻¹). CO₂ emissions ranged from 200 mg m⁻² h⁻¹ during the rainy season (winter) and >500 m⁻² h⁻¹ during the growing season. Though no differences were detected in CO₂ emissions between irrigation practices, mean CO₂ emissions under WLCC were 40 % and 15 % greater compared to NCC under FI and SDI, respectively. The treatment with the greatest effect on CO₂ and N₂O emissions was WLCC, which increased average growing season N₂O and CO₂ emissions under FI by 60 μg N₂O m⁻² h⁻¹ and 425 mg CO₂ m⁻² h⁻¹ compared to NCC. In SDI there was no effect of a cover crop on growing season CO₂ and N₂O emissions. In the rainy season, however, SDI N₂O and CO₂ emissions were not different from FI. In the rainy season, the cover crop increased N₂O emissions in SDI only and increased CO₂ emissions only under FI. Subsurface drip shows promise in reducing overall N₂O emissions in crop rotations with legume cover crops.