Avaliação da água de escoamento em pastagem de sorgo forrageiro com diferentes doses de dejeto líquido de suíno

Abstract

Given the environmental problems mainly related to the quality and availability of water resources currently observed, has aroused great concern in society, especially in relation to production processes. Given this agriculture from the change to a style of intensive production, now seen as potentially polluting activity, where the swine, stands out with high importance for being the main source of animal protein consumed worldwide. However, as a result of this activity, the generation of waste has been intensified, and consequently the concern about its applicability and destination, due to the increasing impact that such waste has caused mainly by virtue of Nitrogen and Phosphorus are the main contributors of eutrophication of water resources. In this context, this study aims to evaluate the application of pig slurry (DSL) as the sole source of nutrients in topdressing pastures, forage sorghum, relative water losses by runoff, the amount the total nitrogen (N total) in the same and production in Green Mass (MV) and Dry Mass (MS). Rainfall events are given by natural rainfall and irrigated. The study was experimental type, developed from plots with complete block doth using four treatments with four replications, with DSL doses (0, 40, 80 and 160 m³. há-1) corresponding to (0, 3, 6 and 12 kg ha-1 of total N) respectively. The use of DSL in the pasture was held 20 days after emergence, with quantified water losses by runoff through the installation of sewer gutters in each plot and measured the concentrations of total N present in this by chemical analyzes of water runoff. The losses of total N were very low, being directly influenced by the amount of N applied through DSL, where the greatest losses of both total nitrogen as water runoff were at the highest dose (160 m³.ha-1 of DSL, equivalent to 12 kg ha-1 of total N), corresponding to losses of 0.35 kg ha-1 total N, which is insignificant for the contamination of water resources. The production (MV) and (MS) were significant, and positive response to fertilization according to the dose, even at low concentrations of nitrogen. The different rainfall events did not possess significant effects on total N losses, probably due to low concentration element in DSL applied.