Evaluation of soil conditions in fast-growing plantations of Eucalyptus grandis and Acacia mangium in Brazil: A contribution to the study of sustainable land use

This study is a comparison of the holorganic horizons (L and F) and hemiorganic horizons (A11 and A12) of 7-years-old stands of Eucalyptus grandis and Acacia mangium, in the region of the Tabuleiro Forest, in Linhares, Espírito Santo, Brazil. In the soil under A. mangium, the stocks of organic matter in the L and F horizons were higher, and the C/N ratio was lower, due to the high nitrogen content of the leaf material. The same was observed for the A horizon chemical properties: the C and nutrients concentrations of the soil fine fraction were higher under A. mangium. The comparison of the C and nutrient concentrations between the A11 and A12 horizons and between the aggregate fraction and fine fraction showed similar trends in both sites. In both plantations, the C and nutrient concentrations were higher in A11 than in A12 horizons, and the soil aggregate fraction had higher concentration of nutrients than the soil fine fraction. Nevertheless, the percentage of aggregates in the soil matrix was much higher in A. mangium than in E. grandis. These results show that in this superficially sandy soil (Argissolo Amarelo Distrófico - Ultisol), the organic matter is the most important way of keeping nutrients, and that the aggregate fraction can be the most effective way of avoiding nutrient loss to the deeper soil horizons. In this context, A. mangium provides better conditions for restoring the soil fertility and soil biodiversity, thus providing better sustainability of the cropping systems than E. grandis. © 2004 Elsevier B.V. All rights reserved