Soil biochemical activities as affected by different tillage, fertilization and depth in a semiarid mediterranean agro-ecosystem.

Soil enzymes respond rapidly to changes in soil managements, and therefore are used as early and sensitive indicators of changes in soil properties induced by tillage and additions of fertilisers (Salinas-Garcia et al., 1997). The aim of this work was to compare the effects of different tillage (no tillage, minimum tillage, conventional tillage), fertilization (fertilization versus no fertilization) ad soil depth (0-30, 30-60 and 60- 90 cm) on the microbial biomass and enzyme activities in a semiarid Mediterranean agro-ecosystem. This study finds differences in the microbial respiration parameters and enzymatic activities among the different soil depth. In particular, growing microbial biomass and total microbial biomass reduced with depth with the lengthening of the T-Lag and these results are related to the reduction of oxygen in the deepest soil layer and to the change of the microbial community. The activities of β-glucosidase and N-acetyl-β-glucosidase reduced with depth (lower Vmax) presumably due to the reduced C content in the deeper layers of soils. The fertilization reduced the microbial respiration parameters, while under no tillage, all enzymes demonstrated higher potential activity in top layers of fertilized plots as compared with non-fertilized plots. Tillage smoothed the differences in microbial respiration parameters and max activity of the enzymes, while the activity of all enzymes appeared slightly higher under no tillage with respect to minimum and conventional tillage. This technology can be considered a rapid method for the study of microbial activity in semiarid Mediterranean agroecosystems.