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Denitrification Intensity and Capacity of Three Irrigated Alberta Soils¹

ABSTRACT

Samples from three Alberta soil profiles were used to investigate the denitrification intensity of the soils as related to depth. At 20°C, the intensity was high at the surface and decreased exponentially with depth. The temperature dependency of the intensity on several samples was also studied. By combining the depth and temperature dependencies, the denitrification intensity was predicted for an arbitary temperature and depth. A simple mathematical formulation relating soil temperature with seasonal time and depth was substituted, thus enabling the calculation of denitrification intensity at any time of the year. The calculation indicated that denitrification activity was restricted in the deep hrozions in December and January and in the surface horizons in early May. There was no activity throughout the soil profile in February and March. Loading capacity of a soil for nitrate N expressed as input rate (flux) was equal to the denitrification capacity which was obtained by integrating the intensity throughout the soil profile. The values were approximately 70 kg N ha^–1 day^–1 in August and 5 kg N ha^–1 day^–1 in December. The maximum allowable nitrate concentration is directly proportional to the denitrification capacity and inversely related to the percolating water speed.

¹ Contribution from the Department of Soil Science, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.

² Professor and Technician, respectively, Dep. of Soil Science, Univ. of Manitoba.

³ Research Scientist, Agriculture Canada, Lethbridge, Alberta, Can.

Received for publication December 5, 1978. Accepted for publication April 30, 1979.