Soil aggregation, organic carbon and CO2 emission in different land uses in Brazilian savanna, triangulo mineiro region

Abstract

Soil aggregation and carbon distribution are important indicators of soil quality. Moreover, these attributes are closely related to CO2 fluxes in the soil-atmosphere interface. We sought to evaluate soil aggregation, organic carbon distribution and CO2 evolution in different land uses of Minas Gerais Triangle. Four different land uses were selected: (1) Panicum maximum, (2) Panicum maximum Jacqvr. (Tanzânia), (3) sugarcane, and (4) native Cerrado (control). In each land-use type, soil samples from a 0-10 cm layer were collected. The samples were air-dried and sieved in order to obtain aggregates sized 4-2 mm. The samples were submitted to wet-sieving to evaluate stability and also to obtain aggregates of different sizes: 4-2 mm; 2-1 mm; 1-0.5 mm; and 0.5-0.25 mm. Total organic carbon, humic substances and texture were determined for each aggregate size fraction. The CO2 emission was measured in field and lab conditions, both by the capture in NaOH solution method. The native Cerrado and Panicum maximum Jacqvr. (Tanzânia) areas (mostly clay) showed the highest soil aggregation. The conventional soil tillage adopted in sugarcane areas contributed significantly to aggregate disruption. In all of the areas, the largest aggregates had higher organic carbon and humic substances. Organic carbon content and soil texture seem to be closely associated with CO2 emissions in the areas studied.