Emissions of CO2, N2O, and NO in conventional and no-till management practices in Rondonia, Brazil

Efforts to restore productivity of pastures often employ agricultural management regimes involving either tillage or no-tillage options combined with various combinations of fertilizer application, herbicide use and the planting of a cash crop prior to the planting of forage grasses. Here we report on the emissions Of CO2, N2O and NO from the initial phases (first 6 months) of three treatments in central Rondonia. The treatments were (1) control; (2) conventional tillage followed by planting of forage grass (Brachiaria brizantha) and fertilizer additions; (3) no-tillage/herbicide treatment followed by two plantings, the first being a cash crop of rice followed by forage grass. In treatment 3, the rice was fertilized. Relative to the control, tillage increased CO2 emission by 37% over the first 2 months, while the no-tillage/herbicide regime decreased CO2 emissions by 7% over the same period. The cumulative N2O emissions over the first 2 months from the tillage regime (0.94 kg N ha(-1)) were much higher than the N2O releases from either the no-tillage/herbicide regime (0.64 kg N ha(-1)) or the control treatment (0.04 kg N ha(-1)). The highest levels of N2O fluxes from both management regimes were observed following N fertilizations. The cumulative NO releases over the first 2 months were largest in the tillage treatment (0.98 kg N ha(-1)), intermediate in the no-tillage treatment (0.72 kg N ha(-1)), and smallest in the control treatment (0.12 kg N ha(-1)). For the first week following fertilization the percentage of fertilizer N lost as N2O Plus NO was 1.0% for the tillage treatment and 3.0% for the no-tillage treatment.