THE COPPER FERTILITY OF SASKATCHEWAN SOILS

Abstract

A survey of the DTPA-extractable Cu levels of approximately 1000 fields representing a large number of soil types in Saskatchewan suggested that, under current cropping systems, Cu deficiencies appear to be concentrated in the Grey Soil Zone. They are especially probable in seven soil associations, which include light Transition of Grey and Brownish-Grey Podzolic soils. Soil criteria for detecting Cu deficiencies in cereal crops cannot be fully documented using conventional calibration tests and techniques. However, data from 21 field trials and a growth chamber study indicated that the critical level of DTPA-extractable Cu in these soils is approximately 0.4 mg∙kg−1 for cereals. Large spatial variability of DTPA-extractable Cu levels has been found to occur in a level field, thus suggesting that the Cu status of a field may not be adequately described by assessing the Cu levels of composite field samples. Key words: DTPA-extractable Cu, soil survey, critical level, spatial variability