AVALIAÇÃO DE ATRIBUTOS EDÁFICOS EM ÁREAS DE PASTAGENS EM RELEVO MOVIMENTADO EM ITAPERUNA-RJ

The study was carried out in Fazenda Pau Ferro, Itaperuna - RJ, to evaluate soil quality attributes in pastures areas, Braquiária (Brachiaria brizantha (Hochst. ex A. Rich.) Stapf), Suázi (Digitaria swazilandensis Stent) and Tifton 85 (Cynodon spp. cv Tifton 85) cultivated in hill relief. Soil samples were collected at 0-10 and 10 -30 cm depth in two times; dry period (August of 2004, May of 2005 and August of 2005) and in the rainy period (December of 2004) in different sections: at the hillside shoulder (TS), backslope (TM) and footslope (TI) positions. In the samples soil chemical and physical analyses were accomplished. Were evaluated the soil aggregate stability; the bulk density (BD) and the total volume of pores (TVP), total organic carbon (TOC) and soil fertility. To study the multidimensional effect of soil attributes the Principal Component Analysis (PCA) was applied. The pastures areas showed a good aggregation levels, in the different times and depths evaluated. The grasses Tifton 85 and Braquiária propitiated a higher TOC contribution in the depth of 0-10 cm and also larger aggregate weight in the class> 2,0mm, in the dry period. Higher values of BD were observed in the TI. In the rainy period it was observed a BD reduction and TVP increase, mainly for the Suázi areas. In a general way, the positions of the hillside TS and TM were the ones that showed the higher values for the physical and chemical attributes indicating a better soil quality in these areas. In the TI area the lowest levels of soil quality were observed, possibly for the accentuated steepness of this last position of the slope in relation to the other positions. The PCA separated the areas in function of seasonal variation. The dry season presented the higher correlation values with soil quality attributes such as the aggregation indexes and TOC. The aggregate weight distribution in function of the size classes, especially > 2,0 mm, MGD, MWD and TOC were a indicative sensitive to the effects of the treatments, grasses types and seasonal variation.