Effects of Zinc Fertilization on Yield and Tissue Concentrations of Manganese, Copper, Iron and Zinc in Leaves and Seeds of Different Haricot Bean (Phaseolus vulgaris L.) Varieties in Southern Ethiopia

Abstract

Although required in smaller quantity, micronutrients are as essential as macronutrients for optimum growth and yield for beans with adequate tissue concentrations of generally below 100 parts per million (ppm). The experiment was executed in a quadruple factorial design on farmers’ fields and in a greenhouse to evaluate the effect of Zn fertilization on the yield and concentrations of Zn, Fe, Cu and Mn in tissues of different haricot bean varieties grown in soils of Halaba, Butajira and Taba. The treatments include zinc fertilizer (0, 0.5, 1, or 1.5%) and haricot bean variety (Nasir, Ibado, Hawassa Dume, or Sari-1).  The results indicated that yield and tissue micronutrients contents of haricot bean varied significantly among the different locations (soils) the highest yields under greenhouse (17.62 g/pot) and at field (3553.6 kg ha^-1) being obtained in Butajira soils. Variety Nasir was the best both in yield and Zn and Fe concentrations of seeds. Yield of haricot beans and tissue concentrations of Fe, Cu and Mn were not significantly affected by Zn fertilization, but both leaf and seed Zn concentrations were significantly increased. The highest leaf Zn and seed Zn, 50.71 and 20.53 mg kg^-1, respectively, were obtained at applications of 3 and 2% ZnSO₄.7H₂O, respectively. We can, therefore, conclude that foliar Zn fertilization is vital to increase the grain Zn content of haricot bean which in turn can contribute to alleviated Zn deficiency of people who depend on haricot bean diet for their Zn source. Consequently, foliar application of 2% ZnSO₄.7H₂O is recommended for significant increase of grain Zn content of haricot bean.

Keywords: Manganese, Iron, Copper, Zinc, Concentration and Haricot bean