SEASONAL-VARIATIONS OF SOIL MICROBIAL BIOMASS CARBON WITHIN THE PLOW LAYER

Over 31 months microbial biomass-C was estimated using the substrate induced respiration technique in fields with conventional soil management, where sugar beet-winter wheat-winter barley were grown in a crop rotation. Analysing the plough layer at different depths (0-10, 10-20 and 20-30 cm) seasonal variations were observed in the amount of microbial biomass-C due to soil and crop management. Although after ploughing microbial biomass-C distribution was homogeneous, a gradient, with decreasing amounts of biomass-C with depth, developed within the plough layer during the early growing season. This was due to a rapid increase of microbial biomass-C in the surface layer (0-10 cm). Throughout autumn and winter there was no change in microbial biomass-C distribution with depth. Within the crop rotation microbial biomass-C content increased in the order sugar beet, winter wheat and winter barley.