Effects of Drying and Air‐dry Storage of Soils on Their Capacity for Denitrification of Nitrate

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The effects of drying and air‐dry storage of soils on their capacity for denitrification of nitrate were studied by determining the influence of these pretreatments on the ability of soils to reduce nitrate to gaseous forms of nitrogen (N 2 , N 2 O, and NO) when incubated anaerobically with nitrate for various times. It was found that drying of soils markedly increases their capacity for denitrification of nitrate under anaerobic conditions and that the effect observed increases as the temperature of drying is increased from 25° to 100°C. Partial drying of soils and storage of air‐dried soils also lead to a significant increase in their ability to denitrify nitrate under anaerobic conditions. Determination of the CO 2 produced when fieldmoist, partly dried, air‐dried, and air‐dried and stored soils were incubated anaerobically with nitrate showed that production of CO 2 was very highly correlated ( r > 0.96***) with production of (N 2 O + N 2 )‐N. This suggests that drying and airdry storage of soils increase their capacity to denitrify nitrate under anaerobic conditions by increasing the amount of soil organic matter readily utilized by denitrifying microorganisms.