ESTOQUE DE CARBONO E FRAÇÕES DA MATÉRIA ORGÂNICA EM ÁREAS SOB SISTEMAS AGROFLORESTAIS E AGRICULTURA NO AGRESTE PARAIBANO

Abstract

Changes in land use from anthropogenic action, most often to the formation of new agricultural areas, affect the dynamics of organic matter as well as the accumulation of carbon in the soil, and are associated with greenhouse gas emissions. The modification of native areas does not imply a decrease in the carbon content, but depending on the form of land use, these contents can increase with the accumulation of organic matter in the soil. The benefits generated by agroforestry systems (SAFs) to the environment are proven in the most diverse regions of the world. However, in the semi-arid region of Paraiba, few studies have been carried out, including the advantages attributed to this type of system in terms of soil carbon. The objective of this work was to estimate the carbon stock and soil organic matter fractions under agroforestry systems and agriculture in the state of Paraíba. The study was carried out in two agricultural properties in the city of Esperança, located in the Agreste region of Paraíba. Three areas with two forms of use were studied: 15-year agroforestry system (SAF-15), 1-year agroforestry system (SAF- 1) and area under conventional agriculture (AC). In each area, 3 quadrants of approximately 25 m2 were delimited and 5 simple samples were collected in each quadrant at depths of 0-10, 10-20, 20-40 and 40-60 cm , The chemical analyzes were carried out in the organic matter laboratory of the UFPB. The variables carbon stock, light fraction, humic substances and particulate organic carbon were evaluated. The areas with SAF-15 and SAF-1 presented higher C stocks at all depths, while for C of the light fraction with also the C associated to the fulvic acid and humic acid fractions, in the SAF-15 area were higher up to the The first area 10 cm, different from the organic C particulate where the same area presented the highest values in all the evaluated layers, the area of AC presented the highest levels of the humina fraction in the last layer studied.