Cold storage of a tropical soil decreases nitrification potential

Abstract

Recommendations for soil handling when determining microbial attributes often include cold storage in the interim between collecting and executing an assay, even if the storage period is likely to be short. Cold storage may not be appropriate for isothermic tropical soils where microbial communities are not adapted to low temperatures. The objective of this experiment was to determine the effects of a short period of cold storage on nitrifying bacterial activity in an Oxisol from eastern Amazonia. Soil samples were collected from primary forest, active pasture, and secondary forest in eastern Amazonia; half were stored at 4°C for 5 d and the other half were incubated immediately. Nitrification potential was determined using a slurry incubation assay. Cold storage reduced the absolute value obtained from the nitrification potential incubations However, relative ranking of the ecosystems was the same for stored and fresh samples. Therefore, storage for short periods at room temperature may be the best treatment for tropical soils. However, when the objective is to obtain a relative index of nitrification, cold storage may simply reduce the sensitivity of the method.