Estrutura e funcionalidade do sistema poroso do solo em sistemas com uso de plantas de cobertura

Abstract

The soil structure and the porous system are essential for the soil to perform its environmental functions. The use of cover crops can be a useful tool for improving the functionality of the soil due to the contribution of carbon to the soil and root growth of crops. Thus, the objective of this work is to evaluate whether the use of cover crops influences the soil structure and the soil porous system functionality. For this, six treatments were evaluated: Bare soil - SD; Forage peanuts - AF; Pensacola grass - GP; Spontaneous vegetation - VE; Black oat + Radish (winter) and Cowpea beans (summer) – AN+F; Black oats + Vetch (winter) and Cowpea beans (summer) – AE+F. An experiment implemented in 2016 in the experimental area of the Soil Department of the Federal University of Santa Maria, in an Hapludalf. Three studies were carried out: in the first study, the soil structure was evaluated through the use of ultrassonic energy. Soil samples were collected in the 0 to 0,05 m layer and applied energies of 0.75; 1.5; 3; 6; 12; 18; 24 and 32 J ml-1. In the second study, the state and functionality of the soil porous system were evaluated through analyzes of soil density, total porosity, soil microporosity and macroporosity and evaluation of airflow in different soil water contents. In the third study, the formation of macropores by different cover crops and the relationship between macroporosity and soil air flows were evaluated. For the studies two and three, samples were collected in the layers of 0 - 0.08 and 0.1 - 0.18 m in depth in PVC rings with 0.095 m diameter by 0.08 m height. The root system and the carbon input by cover crops improved soil aggregation. The AF and GP treatments showed lower dispersion and soil disaggregation index. The AF treatment reduced soil density and improved soil air flows in relation to SD. Maintaining SD reduces the functionality of the soil porous system in the topsoil. The AF treatment showed the highest volume of macropores evaluated using X-ray Computed Tomography. The air flows that occur in the soil are macroporosity dependent in the soil.