Abstract

The decomposition/mineralization of organic material from crop residues constitutes an important nutrient reservoir for plants. This process produces CO₂ 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 CO₂ 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. CO₂ emissions peaked at 5.45, 10.82, 14.00, 11.92 and 11.20, 14.47, 15.98, and 14.74 µg mol of CO₂ g^-1 s^-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.

Key words: Greenhouse gases, organic matter, urea.