Efeito da disposição de efluentes da bovinocultura no solo e na biomassa vegetal

Abstract

The objective of this study was to determine the microbiological characteristics of percolate in different soil depths derived from the application of livestock wastewater (LWW), and assess the growth of Brachiaria pasture by analysis of forage plant mass. The experiment was conducted on a terrain of the Chacara Santo Antonio, in Brazópolis-MG, Brazil. Every three days, during a period of eight months, a 150 mm blade of LWW was applied on a level terrace with 1 m wide base. The percolate samplers were made of PVC pipes of 0.100 m in diameter, with base caps, to collect the percolate, and were installed at different depths: 0.20 m, 0.40 m, 0.60 m, and 0.80 m. The tubes were drilled in the extent of 0.20 m along the length, depending on the installation depth. The percolate samplers were installed downstream, spaced with 1 m from the base of the terrace and 3 m apart from each other. The control sampler was installed upstream, distanced with 1 m from the from each plot, from which the material was collected and dried at 65ºC for 72 h. The terrace crest. Sampling was conducted between October 2014 and April 2015, at irregular intervals, given that it depended on the incidence of rainfall. For analyzing the forage mass, we used the direct evaluation method with cutting and removal of the forage sampling of forage mass was conducted between March and August 2015. We used a template of 1 x 1 m for sampling the analyzed plant mass. After drying in the oven, the dry weight of each plot was calculated during the monitoring period. The pH values of percolate ranged from 5.2 to 7.0, without showing any tendency of increasing or decreasing in function of depth. The result of the chemical oxygen demand (COD) showed the lowest value (120 mg L–1), while the concentrations in other points ranged from 150 to 240 mg L–1COD. The values of total dry matter (TDM) of the forage varied along the monitoring period and the distance of the LWW launch terrace. The control plot presented average value of 133.1 g TDM and plot 4 an average of 753.29 g, which showed a significant increase in TDM production of the pasture. There was improvement in soil fertility with the increase in pH, P, K, S, Ca, Mg, MO, V, and CEC. The infiltration-percolation system was promising as an alternative to the LWW availability in the soil and increased TDM in pasture cultivated with Brachiaria.