Relative effectiveness of various Cu fertilizers in improving grain yield of wheat after three annual applications on a Cu-deficient soil
The deficiency of Cu is not wide spread in Saskatchewan, but whenever it occurs it can have a serious reduction in grain yield and quality of wheat. A 4-year experiment was initiated in spring, 1999 to study the response of grain yield of wheat to Cu fertilization on a Cu-deficient soil near Porcupine Plain in northeastern Saskatchewan. Relative effectiveness of soil application of four granular Cu fertilizers (# 1, 2, 3 and 4) as soil incorporated (at 0.5 and 2.0 kg Cu ha-1) and seedrow placed (at 0.25 and 1.0 kg Cu ha-1); foliar application of four liquid Cu fertilizers (# 5, 6, 7 and 8 at 0.25 kg Cu ha-1) at four-leaf and flag-leaf stages; and a zero-Cu check was compared in 1999, 2000 and 2001. The wheat crop showed Cu deficiency in the growing season in all the three years. In 1999, the zero-Cu check produced grain yield of 1566 kg ha-1. The grain yield increased to 2709, 2571 and 2555 kg ha-1 with the foliar application of Cu Fertilizers 5, 6 and 7 at the flag-leaf growth stage, respectively. In 2000, the grain yield increased from 1620 kg ha-1 in the zero-Cu check to 2676, 2812, 2697 and 2574 kg ha-1 with the foliar application of Cu Fertilizers 5, 6, 7 and 8 at the flag-leaf growth stage, respectively. The Cu Fertilizer 5 also increased grain yield to 2440 kg ha-1 with the foliar application at 4-leaf growth stage. When incorporated into soil or placed in seedrow or foliar applied at four-leaf stage, the Cu fertilizers were not effective in correcting Cu deficiency on wheat in 1999 and 2000. In 2001, the grain yield in the zero-Cu check was 1262 kg ha-1. With foliar application, the grain yield increased markedly with Cu Fertilizers 5, 6, 7 and 8 at the flag-leaf growth stage, and with Cu Fertilizers 5, 6 and 7 at the 4-leaf growth stage. With incorporation treatments, the grain yield increased with Cu Fertilizers 1, 2, 3 and 4 at 2 kg Cu ha-1, and with Cu Fertilizers 1 and 2 at 0.5 kg Cu ha-1. Some seedrow Cu placements (Cu Fertilizers 1 and 2 at 0.5 kg Cu ha-1) also increased grain yield of wheat. In summary, the results suggest that for immediate correction of Cu deficiency in wheat foliar application of some Cu fertilizers at flag-leaf growth stage can be used, but soil applications of granular Cu fertilizers may take three or more years (depending on soil-climatic conditions and management practices) to prevent any Cu deficiency in wheat on Cu-deficient soils.
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