DIAGNOSE DA COMPACTAÇÃO DO SOLO: ABORDAGENS METODOLÓGICAS NA PENETROMETRIA E TEXTURA

Abstract

Soil compaction is one of the main forms of physical degradation associated with the agriculture intensification in tropical environments, compromising root growth, hydrological functioning, the ecosystem services provision, and the agricultural systems sustainability. Despite its relevance, the diagnosis of soil compaction still represents a methodological challenge, mainly due to the limitations inherent in traditionally used indicators, such as soil resistance to penetration and conventional textural characterization, especially in highly weathered soils. In this context, this thesis aimed to evaluate methods for diagnosing soil compaction in tropical environments, with emphasis in the limitations associated with mechanical resistance, textural characterization, and estimation of soil compressive behavior. The research was structured in two complementary chapters. In the first one, soil resistance to penetration was evaluated in the field and in laboratory conditions, based on a database from tropical agroecosystems distributed across different edaphoclimatic regions. The results indicated a high frequency of values considered restrictive to root penetration in field assessments, concentrated predominantly in the surface layers of the soil. However, it was found that the resistance measured in situ shows high spatial and temporal variability, as well as a tendency to overestimate mechanical impedance, reflecting its strong dependence on water content, texture, and structural heterogeneity of the soil. In contrast, laboratory measurements showed greater diagnostic consistency, especially when associated with more stable structural indicators, such as relative soil density and pore system organization, demonstrating that penetration resistance should be interpreted as a complementary functional indicator rather than an isolated diagnostic criterion. In the second chapter, pedotransfer functions were developed to estimate the preconsolidation pressure of Brazilian soils representative of tropical environments, based on easily obtained physical, chemical, and mineralogical attributes. The statistical models obtained had high explanatory power, demonstrating that the compressive behavior of tropical soils is strongly controlled by the interaction between soil water content and fine fraction content, reflecting the combined influence of texture, mineralogy, and structural organization. The results also indicated that these soils have low load-bearing capacity, making compaction practically inevitable under mechanized traffic, even under apparently favorable moisture conditions. Taken together, the findings in this thesis show that soil compaction in tropical environments is a recurring structural condition, conditioned both by intrinsic soil factors and by the methodological limitations of the indicators used in its assessment. It is concluded that the diagnosis of compaction requires an integrated approach between the field and the laboratory, combining the identification of impeding layers with the structural and compressive characterization of the soil, as well as the judicious use of predictive models, contributing to more efficient management decisions and the physical sustainability of tropical agricultural systems.