Samples of Charlottetown fine sandy loam were incubated for 2 weeks at 30°C. and four different moisture tensions, with sand added in four different soil to sand ratios. Tension of 0.24 atm. and 1:1 soil‐sand ratio was optimum for production of NO 3 ‐ ‐N. Incubation in an atmosphere of less than 85% relative humidity severely restricted nitrate production due to drying of the soil. Samples of the same soil at air‐dry, 10% and 20% moisture were stored at −20, −5 and +5°C. for 0.7, 3, 6, 9, 12, and 15 weeks in a complete factorial experiment, then incubated at 30°C. and 0.24 atm. moisture tension for 2 weeks. Air‐drying increased nitrate production by 15 to 20 ppm. N over moist samples. Storage at 20% moisture caused a 2 to 3 ppm. decrease compared to 10% storage. Minus 20° and −5°C. storage gave constant nitrate production with changing storage time, but −20° samples were 2 to 3 ppm. N higher than −5° samples at 10 and 20% moisture. Air‐drying soil from field capacity to the wilting point had little effect on nitrate production, but further drying to the air‐dry state caused a marked increase. Moisture content of soil samples during storage affected the correlation of nitrate production with ryegrass yields in the greenhouse.
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Munro et al. (1964) studied this question.