MICROBIAL ACTIVITY IN SOILS UNDER MEDITERRANEAN ENVIRONMENTAL-CONDITIONS

Thirty-six soils from twelve different arid zones from SE Spain under Mediterranean environmental conditions were characterized by a range of measurements indicative of soil microbiological activity. Our aim was to relate the degradation undergone by these soils with their microbiological and enzymatic characteristics. In general, the soils studied had a low microbiological activity. These soils showed similar values of pH and low total organic-C (TOC) and available nutrient content. The behaviour of dehydrogenase activity was similar to that of CO2 emission and biomass-C, with values ranging from 4 to 148 mug iodo-nitrotetrazolium formazan g-1 of soil. A positive correlation was found between the above indices which, in turn, were negatively correlated with the metabolic quotient values. No correlation was found between these measurements and physical variables such as clay content, pH and WHC of the soils. However, there was a negative correlation with electrical conductivity. The values of urease, protease which hydrolyses N-alpha-benzoil-L-argininamide, protease which hydrolyses casein, phosphatase and beta-glucosidase were, in general, low. There was a positive correlation between the hydrolases of the soils studied. A positive correlation was also found between hydrolases and measurements such as CO2 emission, biomass-C, biomass-C-to-TOC ratio and dehydrogenase.