Growth, Nodulation and Nutrients Uptakes of Cowpea (Vigna unguiculata L. Walp) following Zinc Fertilizer Applications in the Semi-deciduous Forest Zone of Ghana

Cowpea can fix atmospheric nitrogen through symbiotic association with indigenous rhizobia but unfortunately, the amount of N2-fixed is usually not enough due to the presence of ineffective or low numbers of indigenous rhizobia in the soil. The effect of Zinc applications on growth, nodulation and nutrient uptakes of cowpea was investigated during the major and minor cropping seasons (2016). Cowpea seed varieties were treated to foliar spray with three different rates of Zinc sulfate (0, 5 and 10 kg Zn ha-1) at 3 and 5 weeks after sowing. The split plot design was used for both cropping seasons. This study shows that the supply of Zn fertilizer applications did not affect growth and nodulation in 2016 major and minor cropping seasons. The application of the 5 kg Zn ha-1 led to better cowpea production and greatly improve the quantity (haulm and grain yield) and quality (NPK content and crude protein) of cowpea in both haulm and grain. The Zinc fertilizer significantly enhanced N2-Fixed in both cropping season’s trial investigating. These findings suggest that cowpea responds differently to Zinc Sulphate application depending on its rates and the application of the 5 kg Zn ha-1 is the optimum rate that will enhance the yield and nutrient quality of cowpea in the Semi-Deciduous Forest Zone of Ghana.