MICROBIAL ACTIVITY MEASURED IN SOILS STORED UNDER DIFFERENT TEMPERATURE AND HUMIDITY CONDITIONS

Long-term experiments (1, 2 and 20 months) were made to measure the effect of storage on soil microbial activities. Five soils differing in texture and with different C-content: sandy 1.1%, loamy 1.4%, forest mineral layers 5.1%, peaty 11.9% and forest organic layers 34.1% were stored moist at 4, -18 or - 140-degrees-C or air-dry at 21-degrees-C. Indicators for microbial activity included, ATP, heat output and fluorescein diacetate hydrolysis (FDA), showed different effects. The ATP-content in most cases decreased markedly, except in peaty soil and in forest organic layers stored for 20 months at -18, -140 or 21-degrees-C. The beat output was enhanced extremely in peaty soil (except at 4-degrees-C) and slightly in forest organic layers stored at 21 or -140-degrees-C for 20 months. In the other soils storage caused a marked reduction of heat output. FDA-hydrolysis did not change during 2 months in most cases, except in peaty soil, forest mineral layers (-140 and 21-degrees-C) and forest organic layers (21-degrees-C) where it increased significantly during storage. In most cases, air drying caused a significant decrease in the quantity of these indicators of microbial activity. The differences between the effects on samples stored at 4, -18 or -140-degrees-C were slight and in most cases insignificant. The adenylate energy charge (AEC) measured after 20 months of storage was markedly lower in samples of sandy soil and soils derived from forest stored air-dry, while in loamy soil and in peaty soil the results were less clear. The highest AEC values were obtained in loamy soil and forest organic layers stored at -18-degrees-C. The signature indicators muramic acid, glucosamine and ergosterol increased after 20 months storage except for ergosterol in sandy soil, loamy soil, forest mineral layers and forest organic layers (21-degrees-C), where it decreased rapidly.