Resistance to penetration and aggregation of a Yellow Oxisol under monocropping of soybean and eucalyptus in a Savannah of Piauí state, Brazil.

Soil physical quality is essential for sustainability of agroecosystems since it is related to key processes for the development of agricultural crops. The objective of this experiment was to investigate the impacts of soil management on the physical attributes of the soil when cultivated with soybean and eucalyptus monocropping. Soil resistance to penetration, aggregation, and total organic carbon under cultivation of 2 and 4 year old soybean and eucalyptus were evaluated. These results were compared with those of a native forest growing in a Savannah region. Higher resistance to penetration values were found when the soil was prepared by the conventional method and cultivated with soybean. This increment in resistance to penetration increased as depth in the soil surpassed 10 cm, reaching the value of 6.0 MPa, that is, a very high value. The native savannah and the cultivated eucalyptus were the conditions in which resistance to penetration was between low and medium. The system under the conventional system modified soil structure and this caused lower proportion at the larger aggregate classes and aggregate stability index. The monocropping of eucalyptus, due to minimum tillage, was the system capable of preserving the original physical characteristics of the soil. Additional keywords: conventional tillage; organic carbon; soil physical quality. Cientifica, Jaboticabal, v.42, n.4, p.411–418, 2014 ISSN: 1984-5529