Quality of organic matter and carbon in the soil in cultivation of corn with foraging in the function of nitrogen fertilization

Abstract

Nitrogen fertilization in the consortium between forages and maize can modify the chemical composition and quantity of plant residues and, consequently, carbon stock (C), structure and lability of soil organic matter fractions (MOS). The objective of this work will be to evaluate the effect of nitrogen supply (N) for five years in the consortium between corn and forage in the quantity and quality of plant residues, in the contribution of C and N, in the total organic carbon stock and in the degree of humification of soil organic matter. The research will be carried out in an area under direct sowing for five years and cultivated in a consortium system between forages and maize. The treatments were: three species of forage grasses (U. ruziziensis, U. brizantha and P. maximum) and four N rates (0, 90, 180 and 270 kg ha-1) applied in the maize crop. Soil density and total C and N contents will be determined for the calculation of carbon and nitrogen stocks and soil C / N ratio in the layers 0-0.1, 0.1-0.2 and 0.2 -0.4 m. The structural carbohydrates (cellulose, hemicellulose and lignin) of the straw will be determined. It will be estimated the contribution of carbon by the forages and corn, the conversion of C of the residues in C stored in the soil and the evolution of the fractions of the organic matter of the soil. The evolution of the MOS quality by the fractions resulting from the physical and chemical fractionation, the humification index and the lability index (COT / COP) will be studied in relation to the effect of the application of N in the system of consortium, straw quality and contribution of carbon in the system. The maize productivity in a consortium will be evaluated and correlated with the carbon stock and quality of the MOS. The accumulated C and soil carbon stock will be applied in a mathematical model aiming to explain the conversion rate of the C of the residues in carbon stored in the soil and the possible variation of the C stocks in the soil in response to the treatments studied. The data obtained will be submitted to analysis of variance by the F test p <0.05 and presenting significance will be submitted to the t test at p <0.05. (AU)