Soil surface fluxes of greenhouse gases in an irrigated maize-based agroecosystem

An understanding of the effect of fertility management on soil surface fluxes Of CO2, N2O, and CH4 is essential in evaluating C sequestration measures that attempt to increase the amount of crop residue returned to the soil through increased fertilizer inputs. In this study, soil surface CO2 flux was measured over a 27-mo sampling period in continuous maize (Zea mays L.) plots managed under either an intensive fertility regime (M2) or recommended best management (M1). Flux was significantly higher in the M2 treatment on only 2 d during the first growing season. Annual estimates of soil surface CO2 flux, based on a modified exponential equation that incorporates leaf area index (LAI) to predict temporal changes in soil respiration, averaged 11550 kg C ha(-1) yr(-1) for both treatments (approximately 31.64 kg C ha(-1) d(-1) on average). Within row soil surface CO2 flux was, on average, 64% higher than between row flux. Plant population did not significantly affect measured soil surface CO2 flux. While fertility management had no significant effect on CH4 flux, N2O flux as measured on 3 d during the 2000 growing season was significantly higher in the M2 treatment. In 2001, no significant differences in N2O flux were observed, possibly due to changes in N management and irrigation method. Electrical conductivity measured during the 2000 and 2001 growing seasons was significantly higher in the M2 treatment while pH measured during the 2001 season was significantly lower for M2.