Impacto do tráfego de máquinas de colheita da madeira na qualidade física de um Nitossolo Bruno

Abstract

The heavy traffic of timber harvesting machines can cause severe damage to the soil, affecting the quality of physical-hydric resources as well the sustainability of forestry production. Considering that, the purpose of this study is to evaluate the soil compaction and the rut depth formation in Nitossolo Bruno caused by the different traffic intensity of forestry tractors, the direcional feller and the skidder. The study was taken in a forestry company in Campina do Simão, State of Paraná, in Pinus taeda stands with 12 years old and individual average volume of 0,37 m3. The soil studied in the area was classified as Nitossolo Bruno with clay texture. The research behold five kinds of treatment, defined by the following traffic simulation: No Traffic (Control); 1 passage of the direcional feller + 1 passage of the skidder (1 TF + 1 SK); 1 passage of the direcional feller + 2 passages of the skidder (1 TF + 2 SK); 1 passage of the direcional feller + 4 passages of the skidder (1 TF + 4 SK); and 1 passage of the direcional feller + 8 passages of the skidder (1 TF + 8 SK). The soil sample procedure was accomplished by installing four blocks randomly allocated on the plot. The compaction process was determined by the soil bulk density, total porosity, microporosity, macroporosity and mechanical resistance to penetration. The soil furrowing was assessed after the moments of high harvester traffic intensity. The maximum soil bulk density and the optimum moisture to occur the maximum compaction was established through standard Proctor test. The results reveal that the direcional feller and the skidder traffics caused signifcant changes to the physical soil parameters, mainly in the larger traffic intensity and in the soil surface layers. All the measured treatments show mechanical resistance to penetration values above 2 MPa at 0-25 cm layer, value considered as critical level to the plants growing, which reinforces the need to perform the subsoil before implanting the forest. The assay showed that normal maximum Proctor density of the soil to the 0-10 cm layer was 1,25 Mg m-3 and the optimum moisture content was 0,41 kg kg-1, but the average density values soil observed in this study did not reach their maximum value, as well as other layers evaluated 10-20, 20-40 and 40-60 cm. The machines traffic provided for soil furrowing, with higher emphasis to 1 passage of the direcional feller + 8 passages of the skidder, which caused furrows 16,03 cm of depth and 127,87 cm of width. The standard Proctor test revealed that the maximum soil density to the 0-10 cm layer was 1,25 Mg m-3 and the optimum moisture was 0,41 kg kg-1 , however the average values of bulk density observed in this study did not reach their maximum value, as well as the other evaluated layers which presented 10-20, 20-40 e 40-60 cm. In general, the direcional feller and the skidder traffics caused compaction and contributed to furrowing, confirming the need to adopt measures to reduce and control the soil compaction.