INFLUENCE OF VARIED SOIL-TEMPERATURE AND MOISTURE ON MICROBIAL ACTIVITIES UNDER LABORATORY CONDITIONS

Under laboratory conditions the influence of temperature (10-degrees-C, 20-degrees-C, fluctuation from 5-degrees to 30-degrees-C within 12 h with additional freezing for 3 days) and soil moisture (30 %, 60 % w.h.c., remoistening to 60 % for 1 week) on several microbial activities was investigated. The biomass-related, glucose-induced short-term respiration and the dehydrogenase activity (TTC reduction) were higher at 10-degrees-C in most cases as compared to 20-degrees-C. Independent of freezing fluctuating temperature caused the lowest activities. The nitrogen mineralization (including nitrification), however, was affected in the opposite way. No marked influences were observed with beta-glucosidase, arylsulfatase, and alkaline phosphatase. In the sandy loam nearly no effects of the soil moisture occurred and in the loamy sand especially the dehydrogenase activity was higher at 30 % w.h.c., whereas the nitrogen mineralization was lower. From the results it can be concluded, that ecological conditions favouring mineralization without substrate addition may even reduce microbial biomass by decomposition.