Acidez do solo em pastagem após 4 anos de aplicação de água residuária de suínos

Abstract

Swine farming is one of the most important agricultural practices in the world, since pork is widely consumed in several countries, especially in Brazil, which in turn is also an important producer and exporter of food. However, it can result in environmental impacts caused by wastewater (ARS), especially from confinement systems. The work aimed to evaluate chemical attributes of the soil under application of swine wastewater in a single pasture of the species Urochloa decumbens, already established with pasture of Urochloa decumbens in a dystrophic red latosol. Soil samples were collected at depths of 0-20, 20-40, 40-60 cm. The treatments were five doses of swine wastewater (ARS) with 0, 200, 400, 600 and 800 m³ ha-1 year-1, applied in two periods, in the drought and in the water, for the fourth consecutive year annually. Subsequently, the collected samples were dried in an oven with forced air circulation at 45 ºC for 48 hours and evaluated for pH, Al, K, Mg, Ca and OM and from these data, the T, t, V, m and SB were determined. In the statistical analysis, the Tukey test was used for the depth data, with a significance level of 5% and the entire database passed the assumption test. In relation to soil pH and Al levels, it was observed that there was no difference between doses for the same depth and in both depths, the highest value of active acidity was observed in the treatment without application of ARS, indicating that the application changes, even if minimally the values of that attribute. There was no increase in the levels of OM due to the application of ARS and the application of different doses of K, Ca and SB, did not change the concentrations in depth and between treatments. For Mg levels, there was a change between the depths, in which the highest concentration was observed in the most superficial layers, and the low individual levels of the bases reflected in SB values that were equally unbalanced. The values of active CTC (t) only showed variation between the depths in the treatment with application of 600 m3 ha-1 year-1. The value of V% for pastures in the present work was lower than expected, 23.1% and there was a reduction in active acidity in the observed levels, at all depths evaluated. The behavior of the saturation by aluminum (m) was linear and increasing, regardless of the depth and in relation to the Mg content, a quadratic behavior was seen, in which the dose of 250 m3 ha-1 year-1 promoted the highest value. The application of ARS influences soil attributes and its application for 4 years in the cultivation of U. decumbens, changed the acidity of the soil, with reduced pH, increased saturation by aluminum, and did not increase the bases to satisfactory levels.