Efeito do preparo do solo nos atributos físicos e químicos do solo e no crescimento inicial de Pinus taeda

Abstract

The efficiency of soil management in forest sites is of prime importance to ensure an adequate physical environment for tree growth and development. The study seeks evaluating changes in soil physical and chemical properties generated by tillage systems, as affecting fine roots and growth of Pinus taeda in southern Brazil. The study was conducted in a pine stand in Caçador-SC. The experimental design was randomized blocks, with three replications and three tillage methods, namely: Control (C), Hole (H); Subsoiling (SUB). Soil samples were collected, at depths of 0.00-0.10, 0.10-0.20, 0.20-0.30, 0.30-0.60 m, and samples of soil monoliths with roots, at depths of 0.00-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 m, for each tillage system. The chemical, nutrient and pH, and physical properties of the soil, bulk density (BD), total porosity (Pt), macroporosity (Mac), microporosity (Mic), penetration resistance (PR), and quantification of roots fine, root length density (RLD) and fine root density (FRD) were determined for trees 24-months-old. The initial growth of pine, height (H), stem diameter (DC) and volume (V) were determined for trees 12 and 24-months-old. Observed that the soil chemical properties were not affected by the tillage methods, but soil physical properties were improved two years after tillage. The SUB provided a more adequate physical environment, with lower BD and PR, and an increased TP. The H showed adequate values in the first depths of the study (0.00-0.20 m), but decreased with increasing depth. The C showed high values of BD at a depth of 0.30-0.60 m, close to Dsc IHO. The PR was below the critical limit (2 MPa) and restrictive (3MPa) to tree growth in the studied tillage methods. A similar behavior was observed for root traits (RLD and FRD), concentrated in the surface layer (0.00-0.05 m), with 41% and 37%, respectively. The root traits were vertically distributed, with a largest concentration at 0.25 m from the plant. The SUB provided the tallest trees, and greatest stem-base diameter and estimated volume, and provided optimal soil physical conditions for fine root development. Thus, SUB tillage is recommended for Pinus taeda.