Nitrous oxide and methane emissions from a vetch cropping season are changed by long-term tillage practices in a Mediterranean agroecosystem
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Lower greenhouse gas (GHG) emissions from legume-based cropping systems have encouraged their use to deliver mitigation in agricultural systems. Considerable uncertainties remain about the interaction of legumes with long-term tillage systems on GHG emissions under rainfed agroecosystems. In this context, a field experiment was undertaken under a rainfed vetch crop to evaluate the effect of three long-term tillage systems (i.e. no tillage (NT), minimum tillage (MT) and conventional tillage (CT)) on nitrous oxide (N2O) and methane (CH4) emissions for 1 year. Different N2O flux patterns were observed among tillage systems during the growth period of vetch, which depended on the soil conditions favouring nitrification and denitrification. The NT system maintained a higher sink for N2O than MT and CT from January to mid-April, which significantly reduced N2O emissions at this stage. In this period, denitrification capacity and nirK gene numbers were higher for MT than NT and CT. Additionally, an increase in soil NO 3 − content and more favourable denitrification conditions in MT and NT than in CT for the last crop period increased N2O emissions in conservation tillage systems. Total annual N2O losses were significantly higher in MT (124.2 g N2O–N ha−1) than NT (51.1 g N2O–N ha−1) and CT (54 g N2O–N ha−1) in a vetch crop. Low net uptake of CH4 was observed for all tillage systems. These results suggested that long-term NT may be a better option than MT to mitigate GHG emissions in rainfed legume-cereal rotation.
KeywordsNitrous oxide Long-term tillage Methane nirK Vetch crop Soil organic carbon
The authors are grateful to the Spanish Ministry of Science and Innovation and the Autonomous Community of Madrid for their economic support through Projects AGL2009-08412-AGR, AGL2009-12757-AGR and the Agrisost Project (S2009/AGR-1630). This study would not have been possible without technical assistance from the technicians and researchers at the Department of Chemistry and Agricultural Analysis of the Agronomy Faculty (Technical University of Madrid, UPM) and Canaleja field assistants.
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