Saturday, 15 July 2006

Copper Fertilizer Management for Optimum Crop Yield and Quality in the Canadian Great Plains.

Sukhdev.S. Malhi, Agriculture and Agri-Food Canada, Hwy.6 South, Melfort, SK Canada S0E 1A0, Saskatchewan, SK 1240, Canada and Rigas Karamanos, Western Co-operative Fertilizers Limited, Calgary, AB T2P 2N1, Canada.

Deficiency of copper (Cu) in the Canadian prairie soils is not widely spread. But, whenever Cu deficiency occurs it can cause a drastic reduction in seed yield and quality of most cereals, especially of wheat. Successful production of cereals on Cu-deficient soils, particularly wheat, is influenced by rate, source, formulation, timing and method of Cu fertilizer application, as well as levels of other essential nutrients. Surface broadcast followed by incorporation of granular Cu fertilizers into the soil in spring prior to seeding at 3-5.6 kg Cu ha-1 rate was usually sufficient for preventing Cu deficiency in wheat, resulting in improved seed yield and quality. Soil incorporation of lower rates of granular Cu fertilizers (< 2.0 kg Cu ha-1) was not as effective in increasing seed yield of wheat in the first year of application. Compared to granular Cu fertilizers, surface spray broadcast application followed by incorporation of liquid Cu fertilizers at lower rates was found much more effective in preventing Cu deficiency and increasing wheat seed yield in the first year of application. Surface-broadcast application of granular Cu fertilizers without incorporation was much less effective in preventing Cu deficiency and improving seed yield of wheat than incorporated Cu fertilizers. Seedrow-placed granular Cu fertilizers were usually much less effective in increasing 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), Feekes 10 (flag-leaf) and early boot growth stages were very effective in restoring seed yield, while Cu applications at the Feekes 2 (4-leaf) or Feekes 10.5 (complete heading) growth stage did not have 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 and increasing seed yield of wheat, which was associated with the amount of available/soluble Cu in the fertilizer. Stem melanosis in wheat was associated with deficiency of Cu in soil and the disease was reduced substantially with application of Cu fertilizer. High level of available P in soil was observed to induce/increase severity of Cu deficiency in wheat. Soil analysis for DTPA-extractable Cu in soil can be used as a good diagnostic tool to predict Cu deficiency, but the soil test may not provide reliable prediction for Cu fertilizer recommendation on soils marginally deficient in Cu. There was a poor relationship between total Cu concentration in shoots and degree of Cu deficiency, and youngest leaves gave higher correlation than whole plants. Application of Cu fertilizers to wheat on Cu-deficient soils improved several seed quality parameters (kernel plumpness, hectolitre weight and thousand kernel weight), but there was no noticeable effect of Cu fertilization on protein concentration in seed. The increase in concentration and uptake of Cu in wheat seed from Cu fertilization usually showed a trend similar to seed yield. In summary, soil application must be at relatively high rates in order to maintain or build-up Cu levels in deficient soils and get residual benefits for a number of years, but management decisions should consider both immediate and long-term effects of Cu fertilizer on seed yield, seed quality and economics. Foliar Cu application can be used to correct Cu deficiency in wheat during the growing season. Because Cu deficiency in crops often occurs in irregular patches within the affected fields, foliar application may be the most practical and economical way to correct Cu deficiency in the growing season, as low variable rates can be applied according to the degree of Cu deficiency. The findings suggest the need for future research to increase dispersion/dissolution and uniform distribution of Cu ions from granules into the soil for immediate uptake, and develop Cu fertilizer products/formulations that can be used on a commercial scale to prevent and/or correct Cu deficiency in the growing season to optimize seed yield and quality of wheat. More research should be also conducted in relation to soil/plant tissue testing issues in order to detect Cu-deficient soils and promptly prevent/correct Cu deficiency for optimum seed yield and quality of wheat and other crops.

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