Physical soil attributes in areas under forest/pasture conversion in northern Rondônia, Brazil

The main cause of physical degradation in pasture areas is overgrazing, and when combined with poorly productive soils, it causes the loss of millions of hectares of agricultural soils a year. Thus, work is needed to indicate which physical attributes are most sensitive to degradation, generating information so that soil management can be proposed, with a view to economic, social, and environmental aspects. Therefore, the objective of the work was to evaluate the impacts caused on the physical attributes of the soil, in forests converted to pastures in northern Rondônia, Brazil. The study was carried out in three areas within the municipality of Porto Velho, Rondônia, one area with forest and two with pastures (brachiaria and mombaça grass). In the field, deformed soil samples were collected at a depth of 0.00-0.10 and 0.10-0.20 m in the three study areas. In the laboratory, physical analyses of texture, aggregates and porosity, compaction, and an additional analysis of soil organic carbon were carried out. Then, univariate, bivariate, and multivariate analyses were performed, as well as geostatistical analysis. The conversion of forest to pasture had a negative impact on aggregates, compaction, porosity, and accumulation of organic carbon in the soil. The studied environments are influenced by the high levels of sand and clay, which interfere in the aggregation, compaction, porosity, and accumulation of organic carbon in the soil. We observed greater spatial variability of physical attributes in the environment with mombaça grass and attributed this to the greater grazing and trampling intensity of the animals.