The microbial ATP concentration in aerobic and anaerobic Chinese soils

Soil adenosine 5′-triphosphate (ATP) is an excellent indicator of soil microbial biomass in moist aerobic soils, having an extracellular half life of less than 1 h. It is measured by the firefly luciferin-luciferase system. Jenkinson and Oades (1979) proposed a method to measure ATP in aerobic soils, with a reagent of Na2HPO4, trichloroacetic acid (TCA) and paraquat, (TCA reagent). Their method has been superseded by an alternative where paraquat is replaced by imidazole, termed the TIP reagent. Both methods give the same results. We found a constant biomass ATP concentration of 7.9 ± 2.24 μmol ATP g−1 biomass C in aerobic soils irrespective of substrate addition and a much lower, and highly variable concentration of 2.83 ± 0.82 in anaerobic soils. Possible reasons are discussed.