Propriedades mecânicas e trafegabilidade de solos em plantios florestais

Abstract

Mechanization significantly increased the productivity, quality and cost reduction for forests cultivation. However, it may be responsible for environmenral impacts, such as soil compaction, which is a result of traffic, mostly during wood harvesting operations. The objectives of this research were to evaluate the physical quality, trafficability and soil compaction due to traffic of wood harvesting machines of Eucalyptus sp. and developing functions to estimate physical and mechanical properties. The research was conducted in soils coming from implantation areas of Eucalyptus sp., and from an operational area of harvesting of Eucalyptus saligna Sm, belonging to CMPC Celulose Riograndense. To answer the hypotheses and meet the objectives, this work was divided into two studies. In Study I, five forest soils with different textural compositions were evaluated, determining physical quality indicators, trafficability indicators coming from the Proctor Normal test and uniaxial compression, and Atterberg consistency limits. The main results showed that both indicators of physical and trafficability were related to textural composition of soil, being estimated from these, as well as being influenced by different states of compaction. Furthermore, it was found that changing the bearing capacity has resulted in alteration of least limiting water range, which are related and, in this way, allowed to estimate the critical pressure for the plants growth. In Study II, we assessed the effect of different traffic intensities of a Harvester and a Forwarder on a Haplic Cambissol with sandy loam texture in Eucalyptus saligna Sm. stands, by determining the machines contact area and ground pressure exerted on soil, bulk density, pore size distribution, water retention curve, available water content, saturated hydraulic conductivity, air permeability, penetration resistance, compressibility, degree of compaction and shear strength. Were also evaluated the relationship of these properties and parameters. The main results indicated that few machines passes (one pass of Harvester and the four more of Forwarder) resulted in great part in soil deformation and changing in all evaluated properties and parameters. Mostly effects occurred until the depth of 20 cm. However, increasing the number of passes also caused changes in the deeper layers of soil. In general, the effects were higher in the area below within tracks, but, even so, effects occurred in areas between the wheels tracks and outside the areas of machines tracks. It was concluded that actions to minimize the compaction of forest soils should be associated with moisture conditions, traffic intensity and soil type.