COPPER FERTILIZATION OF WHEAT

Copper (Cu)is the micronutrient most often deficient in Saskatchewan. Since Cu is generally thought of as immobile in soil, placement is a critical issue. This research was conducted to compare traditional and new Cu fertilizer forms and placement methods. A field experiment was conducted at five Saskatchewan sites on soils with low DTPA-extractable Cu levels to identify relative effectiveness of Cu fertilization strategies for hard red spring wheat (Triticumaestivum 1.cv. AC Barrie). Wheat yield, tissue and grain Cu concentration, thousand kernel weight and grain Cu accumulation were measured. The ranking of Cu fertilization method in the first year of application from most to least effective, was: foliar Cu (sulphonate) at Feekes 6or 10> broadcast and incorporated Cu sulphate at 5.5 kg ha-1or 11 kg ha-1> broadcast Cu sulphate with no incorporation. Broadcast Cu oxysulphate was ineffective in the first year. Residual effects of soil-applied products were determined atone site in the second year. Incorporation was critical to the success of residual Cu from broadcast Cu sulphate and oxysulphate. Seed placement of Cu oxysulphate or Cu sulphate was ineffective. A second field study, conducted at two locations, considered the effect of Cu-impregnated macronutrients. Results were inconclusive regarding the efficacy of this Cu fertilization strategy for wheat due, in part ,to high levels of Cu in the soil and possible fertilizer N­ toxicity. A column experiment compared the mobility of Cu as a sulphate or chelate in five soils of high and low organic matter and clay contents. Copper movement was restricted in the high clay, high organic matter soils. Copper was found in the infiltrate of all soils treated with Cu chelate, whereas none was found in the soils treated with Cu sulphate, suggesting chelated forms are more mobile than Cu salts in these and similar soils. Where Cu deficiencies are confirmed, foliar application of Cu products are recommended for response within the year of application. For longer-term response, incorporation of broadcast Cu sulphate or oxysulphatemay be more economically effective