Soil aggregates in areas under different intensities of use in the semi-arid region of the Northeast

Abstract

Soil aggregation is directly influenced by management, and organic matter is one of the main responsible for this aggregation. This study aimed to evaluate soil aggregates under different intensities of use in Pernambuco and Paraíba. Soils were collected at ten sites in the states of PB and PE, in selected areas under caatinga vegetation (caatinga preservada, and caatinga raleada) adjacent to the area under subsistence agriculture (cultivated preserved and cultivated degraded). Soils were sampled in the          0.0-7.5 cm layer. After the separation of dry and wet aggregates and determination of the weighted average diameter of wet and dry aggregates. The stability index was calculated by the weighted average diameter ratio of wet and dry aggregates. Regarding the results, the intensity of land use influenced the proportions of aggregates dispersed via wet in all size classes, except the class > 2 mm. It was verified that the proportion of aggregates in the fraction >2 mm was the one that decreased the most between the dry and wet dispersions, with the fraction 1-0.5 mm being unchanged in relation to the dispersion systems. The average dry weighted diameter was not affected by the intensity of land use, however the values of wet weighted average diameter of the preserved and cultivated caatinga areas were higher than those of thinned and degraded cultivated caatinga. The preserved caatinga and preserved cultivated systems showed greater aggregate stability than thinned and degraded cultivated caatinga.