Propriedades físicas e químicas de um solo arenoso sob o cultivo de Eucalypus spp.

Abstract

The study was carried out to evaluate the changes in the physical and chemical properties of a sandy soil after afforestation of an Eucalyptus forest planted in different spacing resulting in several plant population. The initial plant growth was also monitored. It was accomplished an experiment planted with Eucalyptus dunnii Maiden planted on Alfisol (Red Yellow Podzolic) with native grass. The plant spacing used were: 3,50X3,50; 3,50X1,75; 1,75X1,75 e 1,75X0,87 m. The experimental design was a complete randomized block with four replicates. In the initial twelve months was not observed differences in results of soil properties due Eucalyptus exploration. To explore what may occur in this experiment by end of first or second forest plant cycle it was evaluated three areas, in sites side by side. Site 1 Eucalyptus planted 2x1m with 15 years; Site 2 Eucalyptus planted 3x2m with 20 years; Site 3 natural grass. In the experiment, soil samples were taken before the Eucalyptus planting and after twelve months, and layers of 0,00-0,10; 0,10-0,20; 0,20-0,40; 0,40-0,60; 0,60-1,00 e 1,00-1,50 m. In the area 2 (sites 1 to 3) soil samples were taken in four replicates at same soil layers as the experiment area. The soil physical properties measured were: particle size distribution, bulk and particle density, total, macro and microporosity and wet and dry aggregate size distribution. The soil chemical measured were: water pH SMP, Al+++, Ca++, Mg++, K+, available P, N, C and organic matter. In the experiment was measured the diameter 0,10 m and height of plants at three, six, nine and twelve months of age, at twelve months was measured also the DAP and calculated the basal area for plant and basal area for hectare. In the experiment, measuring at twelve months after installation the soil changes were only for macro and microporosity and for aggregation, mainly due to soil tillage and management involved in installation of forest. In the area 2, the Eucalyptus, as well as the planting spacing adopted did not caused soil physical alteration, except for aggregation, which was smaller at native grass field. The changes in soil chemical properties, in the experiment, area resulted in higher pH, Ca and Mg after twelve months. In the area 2 there were higher levels of Al and smaller pH for Eucalyptus forest, whereas the levels of Ca, Mg, P and K were higher in the natural grass. There were higher Ca, P and K in the site 2, 3x2m spacing, where the organic C were higher at layer 0,2 to 0,6m. The plant spacing for the initial twelve months did not affect plant height and canopy radii, however, did affect plant diameter, basal area for hectare at twelve months age. The higher plant diameter were observed for higher plant spacing whereas, the basal area per hectare were higher for narrower plant spacing.