ATP content of soils estimated by two contrasting extraction methods

The ATP content of a series of soils was investigated in relation to various soil properties. Special attention was paid to the discrepancy in ATP, as estimated after extracting with TEA/NRB and TCA. It appears that the first procedure particularly relates to active microbial cells but extracts rather poorly certain types of older microbial biomass. Nevertheless, the TEA/NRB ATP values correlate very significantly with total soil microbial biomass as determined by the CHCl₃ fumigation method. In soils with active growing microbial biomass, the TEA/NRB and the TCA ATP values are about equal. In normal equilibrated soils the TEA/NRB ATP levels average about 40% of the total soil ATP levels. Finally, in densely rooted soils, the TCA ATP levels surpass largely the TEA/NRB levels, but they appear to a major extent to be due to plant cells.