A comparison of soil quality in adjacent cultivated, forest and native grassland soils

Changes in soil quality after 45 years of continuous production of corn (Zea mays L.) by the conventional tillage method (C) compared with adjacent poplar forest (F) and native grassland (G) sites were examined. The investigated parameters were: total and humified organic C, total N, light fraction content and composition, water-soluble organic C (WSOC), water-soluble carbohydrates (WSC), phenolic substances, biomass C, cumulative CO2-C (soil respiration) (C-m), enzyme activities (alkaline phosphatase, protease, beta -glucosidase, urease, catalase and dehydrogenase). Empirical indexes of soil quality were also calculated: biomass C/organic C, specific respiration of biomass C (qCO(2)), death rate quotient (qD), metabolic potential (MP), biological index of fertility (BIF), enzyme activity number (EAN) and hydrolysing coefficient (HC). Results indicate that long-term corn production at an intensive level caused a marked decline in all examined parameters. Between the undisturbed systems, native grassland showed higher values of soil quality parameters than forest site. The indexes most responsive to management practices that may provide indications of the effects of soil cultivation, as well as of the differently undisturbed ecosystems were: organic C, WSC, C-m, protease, beta -glucosidase, urease and HC. Soil enzyme activities were well related with, and not more sensitive than organic carbon.