Produção, decomposição de matéria seca e comportamento de nutrientes em culturas de cobertura no Sul do Brasil

Abstract

In order to understand the dynamics that the residues can provide to the soil, this study was carried out to quantify the dry matter production and decomposition, as well as the nutrient behavior of cover crops. The experiment was carried out at the Paraná Agronomic Institute (IAPAR) of Pato Branco-PR. With a randomized block design with three replications and two factors: cover crops (Oats; Ryegrass; Vetch; Vetch + Oats; Wild radish and Lupine) and days after deposition (0; 14; 35; 70; 106 and 151). The methodology of decomposition bags (Litter bags) was used. At 14; 35; 70; 106 and 151 days after deposition, one Litter bag was collected per experimental unit. The speed of decomposition of remaining dry matter (MSR) of cover crops was determined from the weight difference of the collection periods compared to the initial 30 g and the remaining nutrients (NR) through laboratory analysis. The values obtained were adjusted to a nonlinear regression model of the equation: MSR and NR = A and −kat+ (100 - A) and/or MSR and NR = A−kat+ (100-A)−kbt. Single or intercropped oat cover crop yielded higher dry matter yield (Kg ha−1). It was concluded that the C/N ratio of cover crops were influenced by the decomposition itself and also by the nitrogen fertilization in cover, factors that directly influenced the decomposition rate of the residues. With the exception of vetches, all cover crops have a C/N ratio greater than or equal to 20/1 initially. Decomposition kinetics are similar for all cultures. Nitrogen release does not accompany the decomposition of waste and is temporarily immobilized by cover crops. Cover crop residues have low amounts of phosphorus and release occurs slowly and gradually. Potassium release occurs rapidly to the system, and is independent of other variables. Late management (after full bloom) interferes with the rate of decomposition and nutrient concentration in the wild radish cover crop, but does not interfere with the lupine cover crop. The constant decomposition/release rate (ka) influences the half-life results more than the amount of dry matter/potassium in the labile compartment (A%).