Modelos de capacidade de suporte de carga na avaliação da qualidade estrutural de tecnossolos e latossolos

Abstract

A structural quality of soils (SQS) is crucial for plant growth and crop productivity as it impacts essential processes that determine a suitable soil environment, including water retention, gas exchange, soil organic matter, nutrient dynamics, root penetration, and susceptibility to erosion. Human actions can easily affect the structural quality of the soil, directly or indirectly. While there are several indicators for assessing the structural quality of the soil, the study of pre-consolidation pressures (PCP) and the development of load-bearing capacity models (LBCM) are particularly interesting due to the richness of the results they provide. Various research studies emphasize their utility when analyzed alongside particle size distribution, soil density, total porosity, macro- and microporosity. These methods not only allow for evaluating the initial state of a soil but also prove useful for comparing different layers of the same soil, layers of different soils, and the effect of different soil management practices over time. Considering the multiple assessment possibilities these methodologies offer, their use was aimed at evaluating the structural quality of soils with limitations for plant growth. Initially, load-bearing capacity models (LBCM) were developed and compared for Technosols formed by iron mining tailing resulting from the rupture of the Fundão Dam (Mariana, MG). In these soils, soil density (Ds), particle density (Dp), total porosity (Pt), microporosity (Mic), particle size distribution, and organic matter (OM) were also determined. This research revealed that the formed Technosols exhibit high load-bearing capacity due to high pre-consolidation pressures, a result of the high content of silt and very fine sand particles that determine their compaction. Thus, the mechanical resistance of Technosols is quite significant, posing a limitation for these soils. In the second stage, Oxisols under corn silage agricultural management were evaluated. Two management conditions were assessed: conventional and in succession with soybeans as a more sustainable alternative. Initially, load-bearing capacity models (LBCM) were developed to identify the initial condition of the soils and compare them with native forest to evaluate their initial degradation. Subsequently, soil compaction was assessed over the crop cycles, incorporating confidence intervals into the LBCM and including the PCP values obtained in the different assessments to quantify compaction or recovery. The results demonstrate that the soils under succession had a greater load-bearing capacity at the beginning of the research. However, this system proved to be more efficient in increasing soil resistance to compaction since, at the end of the study, it showed a lower percentage of compacted samples in the two evaluated layers, as well as improvements in Ds, Pt, Mic, and OM. In soils under monoculture, there were no favorable changes in these properties, with an increase in Mic alongside a decrease in Mac.