Organic matter properties in cultivated versus set-aside arable soils

Two arable soil-ecosystems, representative of the north Mediterranean al ea (a sandy italian soil and a spanish silt-loam soil), were selected to evaluate the effects of different agricultural practices on organic matter properties. Within each area, three soil sub-ecosystems, corresponding to different soil uses were sampled: native undisturbed soil, soil in set-aside condition, and intensively cultivated soil. Pyrolysis-gas chromatography has been used as a quick degradative method which gives the chemico-structural composition of the humic substances, the index of mineralization and humification of the organic matter, and the index of similarity between pairs of soil sub-ecosystems. Soils nhich have been used intensively have shown, in both ecosystems, a mineralization of the organic matter appreciably higher than native undisturbed soils, while the degrees of humification did not show great differences in the three soil sub-ecosystems. Differences were also evidenced through the pyrolitic indices of similarity, chemical parameters (C and N compounds) and dehydrogenase biochemical activity. Different uses of soil affected the dynamics of mineralization of the organic matter. Set-aside after intensive cultivation seems to restore soil metabolic activity and soil fertility. (C) 1998 Elsevier Science B.V.