THE ZINC FERTILITY OF SASKATCHEWAN SOILS

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Abstract
Current criteria for predicting zinc (Zn) deficiency in Saskatchewan soils are based on DTPA-extractable Zn values. DTPA-extractable Zn levels in 12% of 1200 samples taken across Saskatchewan contained less than 0.5 mg Zn kg−1 soil and would be classified as potentially Zn deficient. However, 23 field trials in 1982, 1983 and 1984 with spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), lentils (Lens esculenta Moench.), peas (Pisum sativum L.), alfalfa (Medicago sativa L.), corn (Zea mays L.) and flax (Linum usitatissimum L.) produced only one significant response to Zn fertilization. No yield benefits due to either annual or residual application of Zn fertilizer were obtained even on high lime soils or those containing DTPA-extractable Zn levels below 0.5 mg kg−1 soil. Hence, current soil criteria to identify Zn deficiencies under the prevailing cropping systems must be revised to reflect these findings. Key words: DTPA-extractable Zn, crop response, critical level