Effects of conventional tillage on biochemical properties of soils

Modification of soil environment by different farming practices can significantly affect crop growth. Tillage causes soil disturbance, altering the vertical distribution of soil organic matter and plant nutrient supplies in the soil surface, and it may affect the enzyme activity and microbial biomass which are responsible for transformation and cycling of organic matter and plant nutrients. In this study, the influence of three conventional tillage systems (shallow plowing, deep plowing and scarification) at different depths on the distribution and activity of enzymes, microbial biomass and nucleic acids in a cropped soil was investigated. Analysis of variance for depth and tillage showed the influence of the different tillage practices on the activity of some enzymes and on the nucleic acids. Glucosidase, galactosidase, nitrate reductase and de hydrogenase activity were significantly affected by the three tillage modalities. Activity in the upper layer (0-20 cm) was higher in the plots tilled by shallow plowing and scarification than in those tilled by deep plowing. Positive relationships were observed between the soil enzymes themselves, with the exception of urease and pyrophosphatase activity. Moreover, significant correlations were found between DNA and beta-galactosidase, and between RNA and beta-glucosidase, beta-galactosidase, alkaline phosphatase and phosphodiesterase. alpha-Glucosidase, beta-galactosidase, alkaline phosphatase and phosphodiesterase were highly correlated with biomass C determined by the fumigation-extraction method.