Biotests as markers of soil utilization and fertility

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Abstract
Two natural soil ecosystems, representative of agricultural management in a temperate Mediterranean climate, were selected: a sandy soil located at Peccioli Farm, Pisa (Italy), and a silt‐loam soil located at Salamanca, Muñovela (Spain). Within the systems, three areas were sampled (0–10 cm) during the dry season, each corresponding to a different soil use: native undisturbed (NS), cultivated (CS, crop‐pasture rotation) and intensively cultivated soil (ICS, monoculture). Total C, N, exchangeable metals (Mn, Fe, Cu, Zn), ATP, urease, benzoyl‐argininamide (BAA)‐hydrolyzing and casein‐hydrolyzing proteases, phosphatase, ß‐glucosidase, and dehydrogenase were determined and compared. Exchangeable metals, ATP, enzyme activity, C, and N were found to be significantly higher (p = 1%) in native than in cultivated and intensive‐agriculture soils. A good correlation (p = 5%) was found between ATP, hydrolases, C, and N, indicating that all these parameters are related to soil microbial biomass and activity in such “low‐energy”; ecosystems. Dehydrogenase did not correlate with C, N, and protease activities, meaning that the soil ecosystems have low concentrations of exogenous substrates to metabolize, and microorganisms were in a low state of activity. These parameters may be taken as markers of agriculture‐induced changes in soil ecosystems.