NUTRIENT AVAILABILITY AND RECOVERY FROM CROP RESIDUES IN SOIL WITH DIFFERENT TEXTURES

Crop residues on the soil surface not only provide physical protection but may release significant amounts of nutrients to the soil through decomposition. However, the availability of these nutrients to plants has not been sufficiently studied. The aim of this study was to evaluate the total contents of organic C and N, pH, and the availability and recovery rate of P, K, Ca, Mg, and S from the biogeochemical cycling of different crop residues over time in built soils with different textures. The experimental design consisted of a 6 x 4 x 5 factorial arrangement -six treatments, composed of four crop residues (corn, Brachiaria, common bean, and Stylosanthes) and two controls, both without residues, and only one with the addition of inorganic nutrient sources; four different textures formed from the same soil; and evaluation after five incubation times (0, 25, 75, 125, and 175 days). A completely randomized design was used, with four replications. The type of crop residue, soil texture, and incubation time influenced the total concentration of organic C and N, pH, and macronutrient bioavailability and recovery rate. The total contents of organic C and N in soils decreased over the incubation period. The Brachiaria and Stylosanthes residues acidified the soil. Brachiaria residue proved to be a potential source of K, and common bean, of S. The P from corn residue had the highest recovery rate in soils of medium and clayey texture.