SOIL ORGANIC MATTER PARTICLE SIZE FRACTIONS IN SOILS OF THE SEMIARID ARGENTINIAN PAMPAS

Because the level of organic matter in soils can reflect the intensity of soil utilization, the present study was carried out with the aim of elucidating the precise effects of different soil management practices on total organic matter and its particle size fractions in soils of the semiarid pampa region. Surface samples of 52 entic Haplustolls under three different uses (24 under continuous cropping, 18 under rotation with grass leys and 10 virgin soils) were analyzed in terms of clay, total organic matter content and organic matter particle size fractions. The obtained data show that organic matter fractions differ according to particle size distribution and the prevailing soil management system. Stable organic matter content (<50 μm) is significantly related to clay content, whereas coarse organic matter (>100 μm) is strongly influenced by the type of soil management utilized.