Deficiency of copper (Cu) in Canadian prairie soils is not widespread, but whenever it occurs it can cause a drastic reduction in seed yield and quality of most cereals, especially wheat. Field experiments conducted in western Canada indicated that broadcast-incorporation of granular Cu fertilizers prior to seeding at 3-5.6 kg Cu ha-1 was usually sufficient to prevent Cu deficiency in wheat, and improve seed yield and quality. At lower rates (< 2.0 kg Cu ha-1), broadcast-incorporation of granular Cu fertilizers was not effective, while surface spray-broadcast followed by incorporation of liquid Cu fertilizers was much more effective in increasing seed yield of wheat in the first year of application. Surface broadcast without incorporation and seedrow-placed granular Cu fertilizers were much less effective in improving seed yield of wheat than their foliar or soil-incorporated applications. In the growing season, foliar applications of Cu at 0.20 to 0.28 kg Cu ha-1 to wheat at the Feekes 6 (first node of stem visible at base of shoot or stem elongation), Feekes 10 (sheath of last leaf completely grown or flag-leaf) and early boot growth stages were very effective in restoring seed yield, while Cu applications at the Feekes 2 (four-leaf) or Feekes 10.5 (complete heading) growth stage did not have a consistent effect to correct damage caused by Cu deficiency. Some Cu fertilizers (e.g., Cu oxide) were less effective than others in preventing/correcting Cu deficiency. Soil application at relatively high rates produced residual benefits in increasing seed yield for a number of years. The sensitivity of crops to Cu deficiency is usually in the order (wheat, flax, canary seed) > (barley, alfalfa) > (timothy seed, oats, corn) > (peas, clovers) > (canola, rye, forage grasses). Stem melanosis in wheat was associated with deficiency of Cu in soil, and the disease was reduced substantially with Cu application. A high level of available P in soil was observed to induce/increase severity of Cu deficiency in wheat. Soil analysis for diethylene triamine pentacetic acid- (DTPA) extractable Cu in soil can be used as a good diagnostic tool to predict Cu deficiency, but there was a poor relationship between total Cu concentration in shoots and the degree of Cu deficiency in crops. Application of Cu fertilizers to wheat on Cu-deficient soils also generally improved seed quality. Key words: Application time, Cu source, foliar application, granular Cu, growth stage, placement method, rate of Cu, seedrow-placed Cu, soil incorporation, wheat
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