Soil gaseous N2O and CH4 emissions and carbon pool due to integrated crop-livestock in a subtropical Ferralsol

We assessed the impact of integrated crop-livestock (CL), with silage maize (Zea mays L.) in summer and grazed annual-ryegrass (Lolium multiflorum Lam.) in winter, and continuous crop (CC), with annual-ryegrass used only as cover-crop, on net greenhouse gas emission from soil (NetGHG-S) in a subtropical Ferralsol of a 3.5-year-old experiment in Brazil. Emissions from animal excreta in CL were estimated. Soil N2O fluxes after N application to maize were higher in CL (max. 181 μg N2O-N m−2 h−1) than in CC (max. 132 μg N2O-N m−2 h−1). The cumulative annual N2O emission from soil in CL surpassed that in CC by more than three-times (4.26 vs. 1.26 kg N2O-N ha−1, p < 0.01), possibly because of supplementary N application to grazed ryegrass in CL (N was not applied in cover-crop ryegrass of CC) and a certain degree of soil compaction visually observed in the first few centimetres after grazing. The estimated annual N2O emission from excreta in CL was 2.35 kg N2O-N ha−1. Cumulative annual CH4 emission was not affected significantly (1.65 in CL vs. 1.08 kg CH4-C ha−1 in CC, p = 0.27). Soil organic carbon (OC) stocks were not affected by soil use systems, neither in 0–20-cm (67.88 in CL vs. 67.20 Mg ha−1 in CC, p = 0.62) or 0–100-cm (234.74 in CL vs. 234.61 Mg ha−1 in CC, p = 0.97). The NetGHG-S was 0.652 Mg CO2-Ceq ha−1 year−1 higher in CL than in CC. Crop-livestock emitted more N2O than CC and no soil OC sequestration occurred to offset that emission. Management of fertiliser- and excreta-N must be focused as a strategy to mitigate N2O fluxes in CL.