Micronutrients

Abstract

Information is unavailable on the Zn status of entisols and vertisols occupying a large area of the Chad Basin in North‐Eastern Nigeria. Therefore, this investigation was carried out with the above in view. Soil samples from 7 representative profiles were analysed for mechanical composition, pH, organic carbon, available P (0.5M NaHCO₃‐extractable), and available Zn (0.1N HC1‐extractable). Eight bulk soil samples were also collected, analysed for physical/chemical characteristics, and used for Zn response studies. Three plants of corn (Zea mays L.) cv. ‘123 Samaru’ per pot were grown for 7 weeks in 4 kg of soil at 0, 5 and 25 mg Zn kg^‐1 soil. Dry matter yields were recorded.

Available (0.1N HC1‐extractable) Zn ranged from 2.31 to 5.69 mg kg^‐1 with a mean value of 3.83 mg kg^‐1 soil. HC1 extractable Zn was positively correlated with organic carbon content, and had no relationship with other soil properties. There was no definitive depth distribution pattern in different soil profiles, but in clayey soil profiles Zn was generally higher in the surface horizons. Using 4.5 mg kg^‐1 soil of Zn extractable in 0.1N HC1 as the critical limit, about 83% of clayey and 100% of sandy soil samples were found to be low in Zn.

Zinc response in corn ranged from nil to 46%. Significant increases in yield were noted in 2 out of 8 soils and there was tendency for increase in yield in another 3 soils. Yield was generally more with 5 than with 25 mg Zn kg^‐1 soil. The results showed the range of Zn fertilization of crops even under present cropping conditions in the region.