EFFECTS OF STORING SOILS AT VARIOUS TEMPERATURES ON THEIR CAPACITY FOR DENITRIFICATION

The effects of storing soils at various temperatures on their capacity for denitrification of nitrate were studied by determining the influence of storage of field-moist soils at -4, 4 or 30.degree. C for 2, 10 or 30 days on their ability to reduce nitrate to nitrous oxide when incubated anaerobically with nitrate for various times in the presence of acetylene. The data obtained showed that storage of soils at 4.degree. C for 2, 10 or 30 days did not significantly affect their capacity for denitrification, whereas storage at -4.degree. C for 2, 10 or 30 days led to a marked increase in denitrification capacity. Storage at 30.degree. C for 2 days did not have a significant effect on the denitrification capacity of the soils studied, but storage of these soils at 30.degree. C for 10 or 30 days led to a decrease in their denitrification capacity. The effects of storing soils at -4.degree. C on their capacity for denitrification cannot be attributed solely to changes in the availability of soil organic carbon to denitrifying microorganisms as a result of storage because they were evident even when soils stored at -4.degree. C were treated with readily-available organic carbon (as mannitol) before anaerobic incubation with nitrate.