Temporal Variability of Granulometric Fractions of the Organic Matter of an Ultisol in a Transition Area

The absence of vegetation cover associated with the increase of the intensity of use and soil management promotes the medium and long-term degradation of its chemical quality. The management practices adopted can determine if the soil will act in the environment as a source or drain of carbon to the atmosphere, determining the environmental impact of the agricultural activity. These contents, besides varying in the space, vary in the time, therefore the understanding of the variability of the organic carbon in the soil is essential for the improvement of the management practices in the organic systems of production. The objective of this study was to evaluate the behavior of the granulometric fractions of soil organic carbon and its total stocks over three years of cultivation in different systems of organic production management. The areas studied were: (SAF) agroforestry system, (MAR) passion fruit cultivation in monoculture, (ABA) pineapple cultivation in monoculture and (BAN) banana cultivation in a consortium. For comparison purposes, an area under native forest system (MN) was also evaluated. For each system of use, soil samples were collected at depths of 0.0-0.20 and 0.20-0.40 m in four replicates, two collections were done with an interval of three years. The TOC contents were significantly influenced by the isolated effect of the management systems and by the interaction between system and year of management, only in the depth of 0.0-0.20 m. In general, there was a reduction of EstS in all management systems, at a depth of 0.20-0.40 m, with the exception of the ABA system. This shows a higher susceptibility of the oxidation of organic matter in this soil layer. The levels of C-Am were shown to be more sensitive to changes in surface management only. The results showed that the absence of plant cover and the lack of species diversification promoted a decrease in the soil organic carbon stocks. And that the reestablishment of the carbon contents and stocks does not happen quickly and are influenced by the practices and time of handling.