Abstract
ABSTRACT The degree of soil compaction is intensified by its inadequate management, compaction being variable depending on soil type since even under identical management conditions, different types have different abilities to withstand load. The objective of this study was to evaluate the susceptibility to compaction of different classes of soils under no-tillage (NT) croping system compared to the original condition. Thus, i) soils with the same source material have distinct resistance to compression with increased NT adoption time; ii) the most sensitive indicators of this change are the ratios mass:volume and volume:volume and; iii) there is a relationship between resistance and compaction susceptibility with the amount and type of oxide. Soil samples were collected in areas under NT and under natural condition in order to assess the impact imposed by the NT on the attributes density and porosity, precompression stress and compressibility index and relate them to the oxide type of, and content in, the soils under study. The results show that the density and macroporosity were those most affected by the NT agricultural use, regardless of soil type, that is, its dynamic is related more to soil use and less to mineralogical characteristics. The soil resistance and compaction susceptibility were higher in soil developed in basalt, followed by those developed in sandstone and granite. Both the organic matter content and type and concentration of iron oxides were related to the soil resistance and susceptibility to compaction.
Highlights
In southern Brazil soils of the classes of Latosols, Argisols, Cambisols and Nitosols have been intensively used for agriculture, livestock and agriculture-livestock integration systems leading, in many cases, to soil compaction problems
The reduction of the pore volume has been assigned to the static and dynamic pressures on the soil imposed by machines when they work under water content conditions above the soil friability condition (Horn et al, 1995)
The X-ray diffraction analysis of the iron-free clay fraction indicated a mineralogical similarity among soils, with a predominance of the clay mineral kaolinite (Figure 1a)
Summary
In southern Brazil soils of the classes of Latosols, Argisols, Cambisols and Nitosols have been intensively used for agriculture, livestock and agriculture-livestock integration systems leading, in many cases, to soil compaction problems. The reduction of the pore volume has been assigned to the static and dynamic pressures on the soil imposed by machines (soil-tire interface) when they work under water content conditions above the soil friability condition (Horn et al, 1995) Such alterations in soil structure are spread to the crops and there is great difficulty observing and establishing a cause-effect relationship. This is because the compression can not be considered as a value of a single variable, but as the integration and understanding of a set of variables defining a degree of compression, tolerable or not, by the plant. Variables such as bulk density, pore distribution and arrangement, water content, permeability to air and/or water, soil resistance and structure (Horn et al, 1995; Jung et al, 2010; Peng et al, 2012), its development (Bengough et al, 2006; Jung et al, 2010), morphology and root physiology (Bengough et al, 2006; Lipiec et al, 2012), and the development and performance of the aerial part (Jung et al, 2010; Botta et al, 2010) are some of the indicators that help in understanding the degree of compaction
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