An experiment was carried out in pots with three sandy soils from the municipality of Piracicaba, State of Sao Paulo, Brazil, to evaluate the most active period during the decomposition of cornstalk residues and the beginning of the stabilization phase of this process, and also to test the amount of soil carbon and the carbon-nitrogen ratio as decomposition evaluating parameters. A completely randomized block design was utilized with and without the addition of cornstalk residues and with the addition of increasing dosages of nitrogen. The main conclusions were as follows: a) Soil carbon as well as the carbon-nitrogen ratio were adequate as indicators of rate of organic matter mineralization. Carbon content is recommended for practical reasons as it if of easier and faster execution, b) Organic matter decomposition tended to estabilize after approximately 45 days from the beginning of the incubation.
Culture residues; carbon; carbon-nitrogen ratio; organic matter