ASSESSING NITROGEN REQUIREMENTS OF SOME ALBERTA SOILS

Abstract

Fifty Alberta soils, representing the six soil zones of the Province, were sampled for greenhouse and laboratory tests. Five successive crops of oats were produced in greenhouse tests involving a number of different nitrogen applications. In the laboratory the soils were subjected to a number of different nitrogen tests, including three methods of incubation for nitrate accumulation. Analytical data were then correlated with greenhouse yields. Also available for correlation were some data on fertilizer responses in the field.Nitrate nitrogen accumulating in unleached soils after a 2-week Incubation period at 28 °C. showed the best positive correlation with crop yield and the lowest negative correlation with crop response to added nitrogen. Correlation was good, however, only when growing conditions were carefully controlled. Using leached soils for the incubation test or using a 4-week incubating period resulted in lower values. Total nitrogen, 'available' nitrogen, and N values appeared to be of little value in assessing nitrogen requirements: of the soils tested.