Estomation of microbial biomass from ATP content in soil

A newly developed extractant of soil-ATP (TEA/NRB reagent) was compared with an usual extractant of TCA/paraquat on their extractability of microbial ATP in soils and some experimental conditions in the soil-ATP easurement by the TEA-NRB method was established. The TEA/NRB selectively extracted the ATP from microbial cells, although the TCA/paraquat extracted the ATP not only from microbial cells but also from root heirs and nematodes in soils. Some experimental conditions in the TEA method, i. e. the rate of the TEA/NRB reagents to soils, time of ultrasonic treatment and temperature were examined and a rebised procedure of the ATP measurement in soil was proposed. A better correlation between the soil-ATP content by TEA method and the amount of biomass C by chloroform fumigation method was obtained. A mean factor for calculation from ATP content to biomass C was 870 for soils without cropping and c.a. 1100 under cropping. The calculation factor may be depended on the supply of energy source to microbes, cultivation, organic matter content and clay minerals in soil. These results suggest that the TEA method is very useful to measure soil microbial ATP and to estimate microbial biomass and it can be applied to the root-zone soil.