BURNING OF THE SUGARCANE CROP: BIOMASS ASPECTS, SOIL FERTILITY AND CO2 EMISSION IN ATMOSPHERE

The objective of this study was verified if changes in soil, in sugarcane biomass and in atmosphere could be significantly detected after burning. Thus, soil and plant samples were carried out under field conditions before and immediately after burning. The samples were colleted in five standardized areas ( repetitions), and in each area were colleted five samples of soil and plant biomass. CO2 emission was estimated from reductions of total plant biomass after burning. Data were submitted to variance analyses (ANOVA, p < 0.05) and pos-hoc comparisons by Scott-Knott test (p < 0.05). A multivariate statistical analysis, by principal component analysis PCA, was also performed in order to evaluate the interactions among the parameters taking into account in the present study. Results showed significant reduction in biomass of leaves, stem and apexes after burning. However, percentage of apex dry matter as well as corrected Brix did not show significant differences before and after burning. Calculations of CO2 emission showed that 3.89 Mg ha(-1) of carbon was emitted for atmosphere from burned leaves, while CO2 emission from burned apexes was around 0.92 Mg ha(-1), thus, total CO2 emission was around 4.81 Mg ha(-1). Considering soil analyses, there was significant reductions in nutrient contents between before and after burning just in Mn (21.04%), Cu (19.32%), and B (30.56%). PCA analysis show a remarkable difference between before and after burning in all tested areas, mainly because biomass changes. Biomass results showed that the burning reduced in 92.48%, 33.52%, and 30,70% the biomass of leaves, apexes and stem, respectively. Thus, around 10.41 Mg of burned plant biomass emitted 4.8 Mg ha(-1) of CO2 to atmosphere.