IMPACT OF DIFFERENT USE SYSTEMS ON TOTAL AND MINERALIZABLE ORGANIC CARBON IN A SANDY SOIL

O objetivo deste trabalho foi avaliar o impacto de diferentes sistemas de uso nos teores e estoques de carbono orgânico total (COT) e a evolução diária e total do carbono mineralizável (C-CO2) em um Argissolo Vermelho Amarelo de textura arenosa. O estudo foi realizado no município de Eldorado, MS, em uma área de referência de Mata Nativa (MN), e em três áreas manejadas: pastagem permanente (PP), semeadura direta (SD) e área de Reserva Particular de Patrimônio Natural em processo de regeneração natural (RPPN). Amostras de solo das camadas 0,0-0,05, 0,05-0,10 e 0,10-0,20 m foram coletadas para avaliação de densidade do solo (Ds), teores de COT, com posteriores cálculos do índice de estratificação (IE), estoque de carbono (EstC) e variação do estoque de carbono orgânico total (∆EstC), além da determinação da emissão diária e cálculo do acúmulo total de C-CO2. A área de MN apresentou os maiores teores e estoques de COT, chegando a 16,42 g kg-1 e 20,90 Mg ha-1, respectivamente. Já as áreas de PP e RPPN os menores teores e EstC. As áreas de PP, SD, RPPN e MN apresentaram valores de IE de 1,08, 1,13, 1,32 e 1,61, respectivamente. A área de MN apresentou maiores picos e maior acúmulo total de C-CO2. Pela análise multivariada, nenhuma das áreas manejadas se aproximou em qualidade a MN. Os piores resultados nos atributos avaliados são observados nas áreas de PP e RPPN devido ao estágio de degradação destas áreas em função do histórico de exploração e uso do solo.This study aimed to evaluate the impact of different land use systems on total organic carbon (TOC) contents and stocks and the daily and total evolution of mineralizable carbon (C-CO2) in a sandy-textured Argissolo Vermelho Amarelo. The study was carried out in Eldorado, MS, in a reference area of Native Forest (NF) and three managed areas: Permanent Pasture (PP), Direct Sowing b(DS), and an area of Private Natural Heritage Reserve (PNHR) in the process of natural regeneration. Soil samples from the 0.0-0.05, 0.05-0.10, and 0.10-0.20 m layers were collected to assess soil density (Sd), TOC contents, with subsequent calculations of the stratification index (SI), carbon stock (StockC), and variation of the total organic carbon stock (∆StockC), in addition to the determination of daily emission and calculation of total C-CO2 accumulation. The NF area had the highest levels and stocks of TOC, reaching 16.42 g kg-1 and 20.90 Mg ha-1, respectively. On the other hand, the PP and PNHR areas had the lowest content and StockC. The areas of PP, DS, PNHR, and NF presented SI values of 1.08, 1.13, 1.32, and 1.61, respectively. The NF area showed higher peaks and a higher total accumulation of C-CO2, inferring the highest biological activity in this area. By multivariate analysis, none of the managed areas was close to the NF in quality. The worst results considering the evaluated attributes were observed in the areas of PP and PNHR due to the stage of degradation of these areas as a result of exploration and land use history

Influence of land use and occupation on the chemical and physical fractions of organic matter in cultivated and native areas in the Atlantic Forest biome

This study quantified the C content of the chemical and physical fractions of SOM in different management systems in an Argisoil of sandy texture. The study was carried out in a reference area of Native Forest (NF), and in three managed areas: Permanent Pasture (PP), No-Tillage System (NTS) and an area of Private Natural Heritage Reserve (PNHR) in the process of natural regeneration. Soil samples were collected in the layers 0.0-0.05, 0.05-0.10 and 0.10-0.20 m. We assessed the soil density (Sd), total organic carbon (TOC) content, chemical fractionation of SOM with determination of the C contents of the fulvic acids (FA), humic acids (HA) and humin (HUM), with subsequent calculations of the HA/FA ratios, AE/HUM, stock (StockC), physical granulometric fractionation and determination of C contents of particulate organic matter (C-POM) and carbon management index (CMI). Higher TOC contents were observed for the NF area. The C-HA and C-HUM contents were higher in the NF and NTS. NF showed higher C-POM levels in all layers evaluated. For the C-MOM, the NTS area was superior to the other managed areas. The managed areas had lower StockPOM values than the NF. The managed areas had lower CMI values in relation to NF. The NTS area showed that, even in crop succession, it contributes to the improvement of the soil organic fraction over the adoption time. On the other hand, the areas of PP and PNHR showed that inadequate management favors the reduction of edaphic quality