Physical and chemical properties of a dark-red Latosol and agroecosystem sustainability

M. I. N. Alvarenga A. C. Davide About the authors

The agricultural use of soil changes its physical, chemical and biological characteristics. In many instances, these alterations can result in degradation of soil quality, due to destruction of the natural soil cover and excessive use of machines. The objective of this study was to characterize the alterations of some physical and chemical properties of a dystrophic Dark Red Latosol under cerrado vegetation, under different land uses. The soil samples were taken from five different agro-ecosystems: native pasture; improved brachiaria pasture; annual crops; 15 year old reforested land and one year old reforestation with eucalyptus. The soil samples were taken at two depths (0-20 and 20-40 cm), in four periods (November 1993, June 1994, November 1994 and June 1995). The annual crop agro-ecosystem presented the highest difference to the natural cerrado. The more affected characteristics were: K, Ca, Mg, S, P, bulk density, soil microporosity, total porosity and agreggate percentage > 2 mm. In relation to chemical characteristics, higher levels of nutrient were found in soil under annual cultivation as a result of liming and soil fertilization. The annual cultivation leads to soil physical degradation, with increasing microporosity and bulk density, resulting in less root development, and decreasing water availability to the plants. It was observed that among the artificial systems, those which require less intensive managements are the ones which caused less impacts, especially eucalyptus reforestation. Eucalyptus promotes efficient nutrient cycling in deeper layers of the soil profile, with little exportation of soil nutrients, if the cutting at larger intervals is kept.

land use system; cerrado vegetation; Oxisols; properties

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