Vol. 6, Issue 1, Part A (2024)

Zinc deficiency is a global nutritional problem especially in shale soils of tropical region of south-eastern Nigeria. In view of this, the present study was carried out to evaluate the critical limits of Zn for mungbean producing areas and to establish the optimum rates of Zn fertilizer required to achieve maximum Zn uptake and yield performance of Mungbean. Hydrated Zn sulphate fertilizer was applied to the soils at five levels (0, 5, 15, and 20 kg ha^-1) for the greenhouse and at seven levels (0, 3, 6, 9, 12, 15 and 18 kg ha-¹) for the field studies. Results shows that, the shale soils were sandy loam (SL), very strongly acidic (4.73), low in OC (1.08 gkg-1), ECEC (4.38 cmol kg-1) and in EDTA-extracTable Zn (0.52 mgkg-1). The critical limits of Zn for mungbean production soils, were established. Results of the greenhouse and field studies shows that levels of Zn significantly (P<0.05) increased Zn budget, Zn uptake and grain yields of mungbean. Maximum uptake (1.27 mgplant^-1) and grain yields (9.93 kg ha^-1) of mungbean were established at an estimated optimum rates of 13.01 kg Zn ha^-1 and 12.53 kg Zn ha^-1 for greenhouse and field studies, respectively. The current study showed that though the soils had a severe Zn deficiency, the mungbean production could be increased considerably by applying Zn sulphate at 12.5 kg Zn ha^-1 in the soils and other similar soils of the same agroecological zone within a shale derived soil.