Two systems of sugar cane harvesting were compared: 1-previous burning (burned cane) and 2-straw spreading over the soil surface (green cane), over an area of Linhares Agropecuária S.A. plantation, in Linhares, Espírito Santo, Brazil. The soil was classified as Yellow Podzolic sandy over medium texture, developed from Barreiras Formation sediments. After six years of sugar cane cultivation (1989-1994), nutrient distribution, humified fractions, and soil microbial biomass dynamics were determined. The green cane system showed an increasing of soil carbon content in the 0-20 cm soil depth, as well as higher levels of exchangeable magnesium when compared to the burned cane system. However, the burned cane system had the highest levels of potassium and phosphorus in the surface layer. The straw addition resulted in the predominance of humin and fulvic acid fractions and of a greater portion of carbon immobilized in the soil microbial biomass, mainly in the 0-5 cm soil depth, with the highest values observed in the rainy season (November).
soil fertility; humic substances; soil microbial biomass; Yellow Podzolic