Soil CO2 Emission Resulting From Application Of Sewage Sludge Under No-Till.

The experiment has as main aim to assess the CO₂ emissions resulting from application of sewage sludge from a long-time in area under no-till, in Botucatu, State of São Paulo, Brazil. Two types of sewage sludge (centrifuged and biodigested) and four rates applied on soil surface (0, 2, 4 and 8 Mg ha^-1) have been evaluating, with four replicates. Soil CO₂ emission was measured at 1, 3, 5, 8, 15, 30, 60 and 120 days after sowing of soybean 2012/13, using an Automated Flux CO₂ Soil System, model LI-8100A. At the same dates, soil moisture and temperature were measured. The sewage sludge rates have not increased the soil CO₂ emission. As regards to the sludge, the centrifuged sludge promoted greater rates of soil CO₂ emission at 5, 8, 15 and 60 days after soybean sowing (3.8, 2.6, 4.0 and 6.2 mol m^-2 s^-1, respectively). That result may be explained, in part, by soil moisture, which was higher for centrifuged sludge plots. The soil moisture showed significant correlation with the soil CO₂ emission (r = 0.29**). The temperature showed a correlation of -0.15* with the soil CO₂ emission and it seems to have no relation with the results.