Soil moisture as a factor affecting the microbiological and biochemical activity of soil

The purpose of this research has been to identify relationships between soil moisture and the growth and development of microorganisms, their diversity and the activity of soil enzymes. Four soils with different texture were analysed. Air-dry soils were watered up to the moisture content corresponding to 20, 40 and 60% of the maximum water capacity (MWC) and subsequently were submitted to determinations of the counts of soil microorganisms, colony development index and ecophysiological diversity index for bacteria, actinomycetes and fungi. In addition, the response of seven soil enzymes to soil humidity was examined. It was found that the most optimum soil moisture for the development of organotrophic bacteria was the one at the level of 20% of MWC. For Azotobacter spp. bacteria and actinomycetes, the 40% MWC soil moisture level was optimum, while fungi developed the best at the soil moisture level of 60% of MWC. In turn, the activity of soil dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, beta-glucosidase and arylsulfatase was the highest in soil with 20% of MWC. The principal component analysis showed that the soil moisture determined the microbial and biochemical soil activity to a much lesser degree than did the soil type.