Substrates used in SIR assays can inhibit basal respiration in rewetted soil

Abstract

Respiration assays are routinely used for investigating microbial metabolic activity in soil, but usually after a period of "conditioning" whereby dry soil is rewetted and incubated for a period of days. We showed that rewetting and incubation of soil with or without amendments cause changes in microbial populations that are dependent on the type of amendment. As these amendments resulted in altered basal respiration levels and SIR profiles, they call into question the suitability of soil conditioning as pretreatment for soil microbial analyses. When testing soils from an experiment involving various amendments we have found that different substances can inhibit, rather than stimulate, respiration following rewetting. We suggest further investigation of "CO2 burst inhibition" for the purpose of developing a method that does not require naturally dry or air dried soil to undergo conditioning prior to a SIR assay