Impacto ambiental em sistema de pastagem sob aplicações de esterco líquido de suínos

Abstract

One of the main alternatives for the disposal of liquid swine manure is its application into soil. However, this method of disposal requires monitoring of applications because accumulation of nutrients such as copper and zinc in forages and changes in chemical parameters of soil may occur. The experiment was carried out in the experimental area of the Federal Institute of Education, Science and Technology of Triângulo Mineiro - Campus Uberaba, Brazil. The experimental design was a randomized block in which doses of swine manure at 100, 200, 300 and 600 m3 ha-1 year-1 were applied in four replications. The purpose of this study was to: evaluate the influence of liquid swine manure on productivity of dry matter and crude protein; bioaccumulation of copper and zinc in Brachiaria brizantha cv. Marandu and assess changes of soil chemical properties (OM, P, K, S, Cu, Zn and CTC) in the dystrophic red Latosol (LVd) typical to the Brazilian cerrado in the middle region of Triângulo Mineiro. It was found that the successive application of liquid swine manure affected the productivity of dry matter of forage and increased levels crude protein. Brachiaria brizantha cv. Marandu proved to be a bioaccumulator of copper and zinc without the increased absorption promoted by successive application of swine manure to elevate the level of heavy metals to toxic levels for animals. The main changes in soil properties occurred at a depth of 0 to 10 cm. It was concluded that the intensive use of liquid swine manure increased the levels of copper and zinc in soil as a function of the applied doses in periods 2 and 3 and at depth of 0-10 cm. All assessments and doses remained below critical limits adopted by CETESB, one of the supervisory environmental organs. The applications of liquid swine manure did not promote significant increases of pH, organic matter and potassium in the soil at evaluated depths and doses. The concentrations of phosphorus and CTC in the soil increased depending on the doses of liquid swine manure, depth of assessment and collection time. The sulfur concentrations increased depending on applied doses and showed no variation in assessed levels for the collection periods and depths.