Microbial biomass, enzyme activities and carbon stocks in soils as influenced by soil depth, organic and conventional management systems

Many recent studies from around the world have compared organic and conventional farming systems in terms of soil properties. A field study was conducted to determine the distribution of different carbon fractions and the activity of acid Phosphatase, alkaline Phosphatase and Dehydrogenase enzymes in four representative soil profiles one each from < 3years, 3–6 years and > 6 years of organic farming practice and one profile from conventional farming system under central dry zone of Karnataka, India. The activity of dehydrogenase increased significantly in all three organic farming fields irrespective of cropping systems evaluated over conventional farming, with maximum activity being in the profile where organic farming is practicing for > 6years. The organic farming being practiced in < 3 years and 3–6 years fields recorded significantly lower levels of acid and alkaline phosphatase activities in the surface horizon when compared conventional farming system. Depth-distribution studies showed that all the three enzyme activities were concentrated in surface soils and decreased with depth.