A-horizons of 48 Haplic Phaeozems and Kastanozems in plain sites of the Semiarid Argentinian Pampas under three contrasting management systems (virgin bushland. permanent pasture and continuous agriculture) were studied. Morphological characteristics, organic carbon and total nitrogen levels and WE6 ratios were determined on the assumption that both quantity and quality of organic matter should be related to soil textwe of parent materials in this region since other soil forming facton an uniform.The more intensive land use produced an averaged decrease of 7 cm in A-horizon thickness and degradation of soil structure, but little changes in color and propenies of boundaries to AC horizons. In virgin soils organic carbon and nitrogen contents correlate with silt + clay fractions (t = 0.92 and 0.99. respectively), while WMratios are related to clay contents (r = -0.69') confirming the strong influence of soil texture. Agriculturalmanagement and pasture use of soils lead to dispersion of these correlations probably because of differential influence of varying intensities of land use within each management system. Soils under continuous agriculture show lower organic carbon contents than virgin soils only at clay + silt > 40 8. Eragrosris curvulu-pastures seems to be more effective in restoring organic matter and nitrogen levels in sandy but not in loamy soils with respect to virgin soils. This may be due to a better efficiency of E. cuvu&-mots in coarse than in fine textured soils to produce humificable residues than the autochthonous grass species.
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