CO2 Emission In Soils Under Sewage Sludge Amendment In Afforested Areas.

Main objective was evaluating effect of sewage sludge (SS) amendment in CO₂ emissions in soils with different characteristics. Experimental areas were established in 2008 with eucalyptus plantation, with and without SS amendment in two different soils, one sandy and other with more clay (16-20%). Analysis of C0₂ emissions realized in 2011 showed that for sandy soils, with and without SS amendment, practically there were not differences, with mean value of 3.75 mmol m^-2 s^-1. For soils with more clay (16-20%) values of C0₂ emissions were different with, 5.59 mmol m^-2 s^-1 to area with SS amendment, in comparison to 4.13 mmol m^-2 s^-1 to area without SS amendment. These results of CO₂ emissions were consistent with changes in soil carbon content in these different areas, mainly with a noticeable decrease in soil organic carbon in clay soil under SS amendment. Also data of laser-induced fluorescence (LIF) spectroscopy indicated increase of relative carbon compounds stability in the remaining soil organic carbon. This correlation between LIF data and CO₂ emissions suggested that only more stable soil carbon compounds were not decomposed by probably increase in microorganism activity in areas under SS amendment in clay soil.