Chemical soil properties of an inceptisol under long-term sugarcane crops with vinasse application and without slash burning

This study was undertaken in Campos dos Goytacazes, northern State of Rio de Janeiro, based on soil samples of a vertic Fluventic Eutrochrepts, which had been cultivated with sugarcane for several decades. In one situation, the crop had been cultivated for 55 years without burning the residues at harvesting. On another sugarcane plantation, harvest residues had been burned, and vinasse inputs applied by sprinkle irrigation at a rate of 120 m(3) ha(-1) yr(-1) during 35 years. Soil samples were collected from the soil layers 0-0,20 m and 0,20-0,40 in to evaluate and determinate the pH, available P, exchangeable bases, cation exchange capacity, double acid extractable micronutrients, total N, and oxidizable carbon, as well as the fractionation of the humified organic matter. Results indicate that the preservation of crop residue on the soil surface and, to a lesser extent, the addition of vinasse, increase the macro and micronutrients contents. Carbon contents in the superficial layer (0-0,20 m) ranged from 13.13 g kg(-1) in the burned cane to 22.34 g kg(-1) in the unburned cane, and from 15.71 g kg(-1) in the cane without vinasse to 18.33 g kg(-1) in the cane under vinasse application. The improvement of the chemical soil attributes favored the formation of more polymerized alkaline-soluble humic substances.