Tillage impact on soil quality. II. Biological properties in surface soils.

The purpose of our experiments was to determine the response of microbial populations to four different tillage systems (minimum tillage Ml shallow tillage SP, ripper subsoiling RS and conventional deep tillage DP), applied to continuous maize on loamy soil classified as Typic Udifluvent soil. METHoDS. The respiratory activity was determined by incubating the soil at 25 "C with soda lirne pellets. Soit microbial biomass C (SMBC) was estimated using the FI method. Organic C (OC) was determined with a Metfler automafic titrator. The mineralization index (respiratory activity C/organic C ratio) and the metabolic quotient qCO, (respiratory activity C / biomass C ratio) were calculated from the obtained data. Phosphatase activity was determined by incubating the soil with p-nitrophenylphosphate. Rnsurrs. The results of this study refer to the analyses of soil samples taken at depths of 0-15 cm, two years after the start of the experiments. In the minimum tillage system, the respiratory activity, metabolic quotient, mineralization index and phosphatase activity were higher than those of the other tillage systems, while a higher biomass value was found in the ripper subsoiling system. The higher concentration of crop residues in the surface layer and less alteration to the soil structure, inherent in minimum tillage' caused an increase in microbial metabolic activities. Coxcr,ustoxs. After two yearc of using alternative tillage systems, minimum tillage was revealed as particularly favourable towards the development of rnicrobial metabolic activities at depths of 0-15 cm, although it did not influence the conservation of organic mafter and microbial biomass C more than the other tillage systems.