Impacto do uso e manejo do solo na dinâmica do carbono orgânico no sul do Amazonas

Abstract

Soil is the largest terrestrial carbon reservoir and plays a fundamental role in global climate regulation. Its role as a carbon sink or source depends on the management adopted, since soil organic matter is primarily responsible for atmospheric CO2 sequestration. Therefore, the objective of this study was to evaluate the impacts of soil management on the dynamics of soil organic matter carbon. The experiment was conducted at the Mangabeira Experimental Farm (IEAA/UFAM), in randomized blocks with a split-plot arrangement, in a 3x4 factorial scheme, involving three management systems (no-tillage, scarification and conventional tillage) and four lime rates (0, 2, 4 and 6 t ha-1). Soil samples were collected from the 0-20, 20-40 and 40-60 cm layers, at three different times during two crops (rice and corn). The physicochemical analyses followed the methods of the Embrapa soil analysis manual (2017), and the data were subjected to analysis of variance (F test) at 5% significance and compared by the Tukey test, also at the 5% probability level. The results indicated soil density ranging from 1.30 to 1.70 Mg m-3, with lower values in no-tillage. The weighted mean aggregate diameter (WMD) was higher in conservation systems, reaching 6.47 mm in scarification and 6.44 mm in no-tillage with 6 t ha-1 of limestone. The total organic carbon (TOC) content increased from 4.28 g kg-1 (M1) to 10.85 g kg-1 (M3) in areas without liming. It is concluded that direct planting and scarification, associated with adequate liming, promote improvements in soil structure and organic carbon accumulation, with positive effects on soil quality and the sustainability of agricultural production in the region. These results contribute to the advancement of conservation practices and can support policies and technical recommendations aimed at the sustainable development of agriculture in southern Amazonas.