Estudo das pastagens na microrregião de Quirinópolis-GO, por meio do geoprocessamento

Abstract

The main land use in Brazil is pasture, present in all biomes. The Cerrado stands out among the regions developed for the production and export of beef through grazing systems. In agriculture, the exploitation of natural ecosystems due to the replacement of vegetation cover with cultivated areas has been frequent. In this process, a change in soil cover can occur quickly, which, if poorly planned, can lead to degradation. Regarding the management of agricultural areas, the loss of economic, livestock, or forestry productivity stands out, and one of the ways of monitoring vegetation cover is geoprocessing, which is extremely important, being an effective instrument to cover a greater scope of the areas to be monitored, due to the quantity, quality, and precision of aerial images. The objective of this research is to identify and quantify the pasture areas of the municipalities in the Quirinópolis microregion and classify the levels of degradation through satellite data and vegetation indices using geoprocessing, also evaluating the dynamics of land use and cattle herds in the municipalities between 1991 and 2021. The Quirinópolis microregion is located in the Central-West region of Brazil and is composed of nine municipalities. The pasture areas were obtained from the MAPBIOMAS database for the years 1991, 2001, 2011, and 2021. The images used to evaluate the quality of the pastures for the year 2021 were from the Sentinel-2A satellite, using NDVI and the Pasture Degradation Index (PDI). Numerical data on cattle herds in the municipalities of the microregion were acquired from the IBGE database and correlated with the pasture area in each municipality. Approximately 30% of pasture areas are in PDI classes 1 and 2, which are considered optimal; 60% of areas are between classes 3 and 4, which characterize medium-quality areas with low degradation; and another 10% of the areas are in classes 5 and 6, considered to have a high degree of degradation. Approximately 50% of pastures are on land with up to 8% slope, another 30% on land with 8 to 20% slope, and the remainder on more rugged topography. The predominant soil class in the region is dystrophic Red Oxisol, accounting for more than 80% of pasture areas. Most municipalities greatly reduced their cattle herds during the study period, with an average stocking rate between 1 and 1.2 AU·ha⁻¹. It is concluded that the quality of pastures is mostly at a low level of degradation and in relatively flat areas within the dystrophic Red Oxisol class. Geographic databases and computational tools through geoprocessing make it possible to evaluate and quantify pastures on a spatial scale.