Gênese, classificação e mapeamento de solos desenvolvidos de rochas pelíticas em áreas cultivadas com eucalipto em Minas Gerais

Abstract

Because the demand for arable areas has turned very intense in the last years, soils then considered as not appropriate to agricultural use are now being revalued and studied in order to use them for forest plantings, to example of Cambisols developed from pellitic rocks of Bambui Group. In reason of the expressiveness of these soils, usually associated Latossols, it was selected the areas of Farm Olhos d`Água and Cachoeira, Minas Gerais State, whose objectives were: study the physical characteristics, chemistries and mineralogical of the soils; understand the processes of soil genesis; show the space distribution of the soils through semi-detailed mapping, in the scale 1:20.000. The samples of soils were submitted to the physical and chemical analyses of routine, retention of water, total and sulfuric digestion, and mineralogical analyses. It was verified in Cambisols medium tenor of silt of 47%. Some characteristics observed in these soils, as horizontal direction of the origin material, high silt tenors and of density of the soil, kaolinite and illite prevalence in the fraction clay, consistence hard or very hard when dry, and structure in blocks faintly developed contribute to low quality of the forest planting. The smaller capacity of water retention of Cambisols, associated to the low hydraulic conductivity, to the little thickness of the solum and larger difficulty of infiltration of water, in reason of topography and of superficial stamp, seems to be indicative of smaller capacity of water recharge in the areas where they appear, could contribute to the depreciation in the quality of the forest planting. Results of Ki around 2,0 for Cambisols indicate smaller soil genesis and larger kaolinite proportion and illite in the fraction clay, comparatively to Latosols. In this fraction also verified gibbsite and VHE. The silt fraction revealed the presence mainly of mica and quartz and the sand fraction, basically quartz, confirming the low reserve of nutrients in the larger fractions. In the fraction clay of Latosols, kaolinite, illite, gibbsite, and VHE were verified. The gibbsite presence is larger than verified in the fraction clay of Cambisols, to infer for the results of Ki, around 1,4. The low tenors of CaO, MnO, MgO and, mainly P2O5, obtained by the total digestion, revealed the low capacity of reserve of these nutrients in all the studied soils. As for total K2O, the largest tenors in Cambisols indicate larger presence of micas in relation to Latosols.