Zinc responses of dry beans in Manitoba

Close to 80% of dry beans in western Canada are grown in southern Manitoba. A need was identified to develop soil-testing criteria based on local conditions as well as derive an optimum fertilizer rate to alleviate Zn deficiency. Two experiments with a number of dry bean (Phaseolus vulgaris L.) cultivars were carried out between 2000 and 2002 at a number of locations in Manitoba. Each experiment included two trials per year. The first experiment consisted of two foliar application rates of Zn (0 and 0.33 kg ha(-1)) as main plots and five rates of broadcast and incorporated soil Zn (0, 2.8, 5.6, 8.4 and 11.2 kg Zn ha(-1)) as sub-plots. The second experiment also included two rates of foliar Zn (0 and 0.33 kg Zn ha(-1)) as the main plots; however, sub-plots included a control and four Zn products that were broadcast and incorporated at a rate of 5.6 kg Zn ha(-1). Soil DTPA-extractable Zn levels varied from 0.38 to 1.14 mg Zn kg(-1) soil. Soil Zn applications resulted in a significant increase of Zn in plant tissue levels at 1/10 bloom growth stage, however, actual levels varied, thus, suggesting that a plant tissue critical level will have to be derived separately for each cultivar. Significant seed yield responses were obtained only when DTPA-Zn levels were equal to, or less than, 0.5 mg Zn kg(-1). Optimum yields at responsive sites were obtained with 5 kg Zn ha(-1) broadcast and incorporated. All products used (Zn mono- and hepta-sulphate or oxysulphate) performed equally well, except in one case when ZnSO(4).H(2)O exhibited superior performance. Foliar application of a sulphonic acid based Zn product was not always as effective as soil applied Zn products.