ASPECTOS AMBIENTAIS E AGRONÔMICOS DA DISPOSIÇÃO DE EFLUENTE DE LATICÍNIOS NO SOLO

Abstract

The activity of the dairy products is of great relevance in several aspects, among them the financial and the nutritional, but the wastewater coming from their activities are considered major pollutant sources of the water courses receiving these effluents. The use of these wastewater in pastures is an alternative to mitigate the impact on the environment, and also to fertilize the soil, an action that can improve the availability of nutrients and enable the increase of dry matter in fodder. On the other hand, the residual water from lacínios is known to be rich in sodium that is added to the production processes, this mineral according to numerous studies when applied in high concentrations in the soil can impair the absorption of nutrients by the crop and modify the physical properties in the soil, this factor makes it necessary to assess the impacts, and it is important to discuss how the application of these residual waters can become impacting and also the recommendation of their proper concentration. To obtain this information, an entirely randomized design experiment was set up, consisting of five treatments with four repetitions planted with Panicum maximum grass. The treatments were formed according to the sodium concentrations, which is the component with the highest relative concentration in the residuary water used in the studied dairy, the treatments were T1: application of dairy wastewater providing 75 mg L-1 of Na+ ; T2: application of dairy wastewater providing 150 kg ha-1 of Na+ ; T3: application of dairy wastewater providing 300 kg ha-1 of Na+ ; T4: application of dairy wastewater providing 600 kg ha-1 of Na+; and T5: (Witness Treatment) with irrigation water. Soil samples were collected at depths of 0-10, 10-20, 20-30 and 90-100 cm for physical and chemical analysis. Samples of grass were collected for chemical, microbiological and productivity analyses. Statistical analysis consisted of variance and regression analysis, the means being compared using the Tukey test. The results obtained with the experiment allowed the conclusion that the application of dairy wastewater even at high concentrations provided a substantial increase in the productivity of pumpkin grass, maintaining the ideal mineral concentrations of forage and without microbiological contamination. In relation to the soil, it did not provide a significant dispersion of clay in the different depths of the soil, however it is necessary to evaluate for longer periods the effects of the high rates of residuary water due to its potential risk of salinization and groundwater contamination.