Oxisol and Ultisol CO2 Emission after Soil Tillage of Sugarcane Area in Brazil.

Soil tillage can modify soil structure and consequently soil porosity, increasing the soil CO₂ emission. The objective of this work was to evaluate the influence of different soil tillages on CO₂ emission. The study took place in two experimental sites located at Brazil (21º 14’ 05” S, 48º 17’ 09” W), under Oxisol (clay content = 545 g kg^-1 at 0.10 m depth) and Ultissol (clay content = 130 g kg^-1 at 0.10 m depth). A large paired-plot design was used with two treatments and ten replications. The treatments were two soil tillages to sugarcane planting: soil chiseling only in row planting (CR) and soil chiseling on total area (CT). Soil samples were collected at 0.00-0.10 m depth to determine soil organic carbon (SOC) and total porosity (TP). The soil CO₂ emission (FCO₂) was evaluated using the system LI-8100, during 12 days after tillage in both areas. The CO₂ total emissions were estimated by integral value over time. The FCO₂ values were higher on Oxisol for both soil tillages (CR = 1,042.6 kg CO₂ ha^-1 and CT = 1,336.3 kg CO₂ ha^-1), compared to Ultissol (CR = 659.1 kg CO₂ ha^-1 and CT = 702.8 kg CO₂ ha^-1), probably due to the higher SOC in Oxisol (18 g kg^-1) than in Ultisol (7 g kg^-1). In both soils, the FCO₂ values were higher on CT than CR, probably due to the more intensive soil mobilization, as showed the higher TP values on CT (Oxisol = 0.56 m³ m^-3 and Ultisol = 0.33 m³ m^-3) compared to those on CR (Oxisol = 0.49 m³ m^-3 and Ultisol = 0.31 m³ m^-3). These results confirmed the influence of soil organic carbon and soil mobilization on soil CO₂ emission.