CO sub(2) emissions from soil incubated with sugarcane straw and nitrogen fertilizer

The decomposition/mineralization of organic material from crop residues constitutes an important nutrient reservoir for plants. This process produces CO sub(2) and is influenced by biophysical and environmental conditions such as temperature, oxygen availability and the chemical composition of the crop residue. We studied the effect of temperature and nitrogen fertilization on CO sub(2) emissions and the distinct contributions of C from sugarcane residue either left on the surface or incorporated into the red-yellow Oxisol. Incorporated sugarcane residue and N applications produce higher total organic carbon (TOC) mineralization rates when compared to application on the soil surface and without N. Nevertheless, there was no difference between TOC and C in the humin fraction (C-HU) 80 days after incubation. CO sub(2) emissions peaked at 5.45, 10.82, 14.00, 11.92 and 11.20, 14.47, 15.98, and 14.74 mu g mol of CO sub(2) g super(-1) s super(-1) within the first four days of incubation for unincorporated and incorporated residues, respectively. After these first four days, emissions decreased until stabilizing at 40 days after incubation.