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It has been shown that cover crops can enhance soil nitrous oxide (N2O) emissions, but the magnitude of increase depends on the quantity and quality of the crop residues. Therefore, this study aimed to evaluate the effect of long-term (19 and 21 years) no-till maize crop rotations including grass [black oat (Avena strigosa Schreb)] and legume cover crops [vetch (Vigna sativa L.), cowpea (Vigna unguiculata L. Walp), pigeon pea (Cajanus cajan L. Millsp.) and lablab (Dolichos lablab)] on annual soil N2O emissions in a subtropical Acrisol in Southern Brazil. Greater soil N2O emissions were observed in the first 45 days after the cover crop residue management in all crop rotations, varying from � 20.2 � 1.9 to 163.9 � 24.3 m gNm � 2 h � 1 . Legumebased crop rotations had the largest cumulative emissions in this period, which were directly related to the quantity of N (r 2 =0 .60, p= 0.13) and inversely related to the lignin:N ratio (r 2 =0 .89, p= 0.01) of the cover crop residues. After this period, the mean fluxes were smaller and were closely related to the total soil N stocks (r 2 =0 .96,p = 0.002). The annual soil N2O emission represented 0.39–0.75% of the total N added by the legume |
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