Soil organic matter pools under management systems and natural Cerrado vegetation / Compartimentos da matéria orgânica do solo sob sistemas de manejo e vegetação natural de cerrado




Different soil organic matter pools under management systems and natural Cerrado vegetation were studied. These pools were estimated using their carbon and nitrogen contents. Total soil organic carbon and total nitrogen (COT and NT), carbon and nitrogen of particulate organic matter (COP and NP), mineral-associated organic carbon and nitrogen (COM and NM), particulate organic carbon associated with different aggregates size classes (COPA), microbial biomass carbon and nitrogen contents (CBM and NBM) and their relations, and basal respiration as a measure of microbial activity, were determined in this study. Eight treatments were used: seven soil management systems and an undisturbed area of Savanna type vegetation, Cerrado, as a reference. They were: heavy disk harrow and legume species cultivation during twelve years (GP); disk plow and legume species cultivation during twelve years (AD); minimum tillage with chisel plow starting five years after installing the experiment (ESC); no-tillage with biennial crop rotation: grass and legume species as cover crop (PD1); no-tillage with crop rotation and annual cover crops (PD2), no-tillage with annual crop rotation of grass and legume species (PD3), permanent pasture (PAST) and natural savanna vegetation, cerrado (CER). The experiment was established in a randomized blocks design with three replicates to study soil tillage and crop rotation dynamics, with temporal and spatial alternation. Soil samples were taken at five depths: 0-5, 5-10, 10-20, 20-30 and 30-40 cm. Soil samples were collected in February, 2008, at soybean flowering stage. The soil management systems cause changes on soil organic carbon contents mainly on particulate organic matter (>53 μm) and microbial biomass fractions as compared to the Cerrado vegetation. The annual use of plow discs to soil tillage causes increase of associated minerals-organic matter levels. In soil and climatic conditions of Cerrado, the use of no-till system preceded by soil chemical and structural correction has promote a more uniform distribution of particulate organic matter in the profile. The microbial biomass is responsive to changes caused by different soil management systems in the Cerrado


fractionation, particulate organic matter, aggregates, no-till, pasture, microbial biomass, basal respiration manejo e conservacao do solo fracionamento, matéria orgânica particulada, agregados, plantio direto, pastagem, biomassa microbiana, respiração basal.

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