Dissertations and Theses

Summary

Proper management of crop soil and crop residues in agriculture can result in significant decreases in soil CO2 emissions and therefore can help mitigate the greenhouse effect. Two field experiments were conducted in areas of sugarcane production in southeastern Brazil, in order to distinguish the contribution of soil and sugarcane residues, in relation to CO2 loss. In the first field experiment, which was conducted over a period of 50 days, the effect of the presence or absence of sugarcane residues on CO2 emissions was investigated. Total emissions were as high as 553.62 g CO2m-2, and as low as 384.69 g CO2m-2 in the uncovered and vegetated plots, with a density equivalent to 3 t ha-1, respectively. The results demonstrate a significant reduction in CO2 emissions, indicating soil carbon conservation after the application of sugar cane residues to the surface. In the second experiment, the influence of the preparation on the CO2 emissions, in plots with and without crop residues, was studied. To estimate the carbon loss of the soil induced by the preparation, the emissions after the preparation of the plots, without vegetation cover, were compared to those of the plots without preparation. The results indicate that removal of sugarcane residues completely from the soil surface in mechanically harvested areas may result in additional emissions as high as those induced by soil preparation.