Decomposição de resíduos culturais submetidos a diferentes doses de nitrogênio

Abstract

The conservation of organic residues on soil surface is considered an excellent tool in the quest for agricultural systems sustainability. Management practices such as nitrogen (N) application on dry residue, tend to retard the decomposition of these, providing benefits such as increasing the SOM. Thus, the present study was conducted to evaluate the effect of nitrogen on decomposition of the dry soy, corn and cane sugar, as well as its contribution to carbon sequestration in the soil. The experiment was conducted at the Universidade Federal da Grande Dourados, in Dourados-MS, and consisted of a randomized block experiment design, with three residues (soy, corn and cane sugar) and four replications The treatments were arranged in split plots, being the four nitrogen rates the plots and the seven collection times the split plots. Decomposition rates of residues, total organic carbon and labile carbon on soil were analysed. The application of 150 kg ha-1 N on dry soy matter, provided the smallest k (0,0029 g day-1), when compared to the other N doses tested, and consequently increased the residence time of the residue on soil. Already the corn and sugar cane residues when submitted to N addition, increased their rate of decomposition. Beyond that, it was proved the importance of organic residues deposition on the soil, once there were increases of labile carbon in soil in all treatments. Note also the mineral N application as a strategy to get higher levels of labile carbon in soil, since these are essential to the production systems sustainability.