Soil physical quality and carbon footprint in grain production systems in the central region of Minas Gerais

Abstract

The physical quality of the soil directly influences its capacity to store carbon and water. In the central region of Minas Gerais, part of the Cerrado biome and characterized by an irregular rainfall regime, this relationship becomes even more relevant, especially in rainfed agricultural systems. The aim of this research was to assess the physical quality of the soil, the stock of organic carbon, the use of water by plants and the carbon footprint in different management systems under no-till farming, relating these factors to grain yield. The experiment was conducted in the experimental area belonging to Embrapa Milho e Sorgo, in the municipality of Sete Lagoas, MG (19° 28'S; 44° 15'W and altitude of 732 m). The soil in the experimental area was classified as a very clayey red Oxisol, with soybeans as the summer crop. The evaluated treatments consisted of successive cropping systems: post-harvest maize; early maize; post-harvest sorghum; early sorghum; early maize + brachiaria; early sorghum + brachiaria; early brachiaria; post- harvest brachiaria. The crops sown after soybean harvest followed the traditional planting date for the region, while in the early planting treatments the sowing date was brought forward by 16 days. Physical quality was analyzed at depths of 0 – 0.10 m and 0.10 – 0.20 m, using physical indicators correlated with carbon stock, soybean yield and straw production. Water use efficiency was estimated using soil electrical resistivity tomography, and the carbon footprint was calculated using the GHG Protocol methodology, adapted to local conditions. The results showed that the systems intercropped with brachiaria had better physical soil performance, with lower bulk density and greater total porosity. The highest yields were observed in the systems with single crops, but the intercropped systems showed greater potential for long-term soil conservation. The highest electrical resistivity and water infiltration capacity of the soil were found in the intercropped systems, where the crops made better use of the water. The intercropping systems showed moderate potential for reducing the carbon footprint. These findings reinforce the importance of conservation practices for increasing carbon sequestration, improving the soil physical quality and promoting more sustainable agriculture.