Autoria: GOMES, J.; BAYER, C.; COSTA, F. de S.; PICCOLO, M. de C.; ZANATTA, J. A.; VIEIRA, F. C. B.; SIX, J.

Resumo: 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 ug N m-2 h-1. Legume-based crop rotations had the largest cumulative emissions in this period, which were directly related to the quantity of N (r2 = 0.60, p = 0.13) and inversely related to the lignin:N ratio (r2 = 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 (r2 = 0.96, p = 0.002). The annual soil N2O emission represented 0.39-0.75% of the total N added by the legume cover crops. Management-controlled soil variables such as mineral N (NO3- and NH4+) and dissolved organic C influenced more the N2O fluxes than environmental-related variables as water-filled pore space and air and soil temperature. Consequently, the synchronization between N mineralization and N uptake by plants seems to be the main challenge to reduce N2O emissions while maintaining the environmental and agronomic services provided by legume cover crops in agricultural systems.

Ano de publicação: 2009

Tipo de publicação: Artigo de periódico

Unidade: Embrapa Agropecuária Oeste

Palavras-chave: Aveia forrageira, Aveia preta, Avena strigosa, Cajanus cajan, Caupi, Cero labranza, Clima subtropical, Cultivo de cobertura, Cultivos de cobertura, Dolichos lablab, Efeito Estufa, Emisiones de gases de efecto invernadero, Ervilhaça, Feijão de corda, Gramínea forrageira, Guandu, Labe-labe, Legumbres, Leguminosa, Manejo del suelo, Manejo do solo, Pastos forrajeros, Plantio direto, Rotación de cultivos, Rotação de cultura, Solo, Subtrópico, Vicia sativa, Vigna unguiculata, Óxido nitroso