Estudo da pegada hídrica e caracterização quali-quantitativa da água de escoamento superficial da pecuária extensiva em condições de clima tropical

Abstract

In this research, studies were carried out in experimental plots for the determination of the water footprint, qualitative and quantitative characteristics of the runoff water and to compare the real erosion with the values estimated by the Universal Soil Loss Equation (USLE) in extensive dairy production. The experiment was carried out at the farm of Embrapa Gado de Leite, located in the municipality of Coronel Pacheco - MG, using crossbred cattle and meteorological data. Twelve experimental plots were used using three types of forages, Panicum maximum cv. Zuri, Brachiaria decumbens cv. Basilisk and Panicum maximum cv. BRS Quenia, with four spatial replicates for each forage. Green and gray water were calculated from each grass where Zuri was the most efficient and Quenia, both species of Panicum maximum, was less efficient. A single value for blue water was calculated, since the cattle used in the experiment was in all forages, and resulted in 14L kg-1 milk. The average value of water demand among the three weeds was 1,393 m³ kg-1 of milk, which is 11.6% higher than the world average. It is noteworthy that green water ranged from 96% of the total value of water demand, 3% was the percentage of gray water, while only 1% was blue water, indicating that extensive livestock farming impacts less than other systems that need irrigation . The water footprint proved to be a relevant and adequate tool for quantification of water demands, fulfilling what was proposed for the work besides being a flexible methodology. The real and estimated soil loss for Brachiaria was 0.038402 and 0.040086 t ha-1 semester-1 respectively, with values being close enough, however, in the case of P. maximum, the estimated values were approximately 2.3x compared to the total sampled. This result points to an overestimation of USLE in relation to the values observed in the field.