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Nitrous oxide and methane emissions from a vetch cropping season are changed by long-term tillage practices in a Mediterranean agroecosystem

Tellez-Rio, Angela, García-Marco, Sonia, Navas, Mariela, López-Solanilla, Emilia, Rees, Robert M., Tenorio, Jose Luis, Vallejo, Antonio
Biology and fertility of soils 2015 v.51 no.1 pp. 77-88
minimum tillage, agroecosystems, greenhouse gases, legumes, conventional tillage, greenhouse gas emissions, nitrification, cropping systems, soil, methane, Vicia, genes, field experimentation, denitrification, nitrous oxide
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 NO₃⁻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 CH₄was 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.