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 select ed to evaluate the effects of different agricultural practices on orga nic matter properties. Within each area, three soil sub-ecosystems, co rresponding to different soil uses were sampled: native undisturbed so il, soil in set-aside condition, and intensively cultivated soil. Pyro lysis-gas chromatography has been used as a quick degradative method w hich gives the chemico-structural composition of the humic substances, the index of mineralization and humification of the organic matter, a nd the index of similarity between pairs of soil sub-ecosystems. Soils nhich have been used intensively have shown, in both ecosystems, a mi neralization of the organic matter appreciably higher than native undi sturbed soils, while the degrees of humification did not show great di fferences in the three soil sub-ecosystems. Differences were also evid enced 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 m atter. Set-aside after intensive cultivation seems to restore soil met abolic activity and soil fertility. (C) 1998 Elsevier Science B.V.