Evaluation of Some Metals Content and Physicochemical Properties of Some Major Rivers as Sources of Irrigation Water in Mid-Benue Trough

Irrigation Water were sampled from some major rivers in the mid-section of Benue Trough for two consecutive years, 2011 and 2012 and analysed for some metals contents and physicochemical properties. The results showed that irrigation water were slightly (pH 6.5) to moderately (pH 5.5) acidic and good for irrigation with minimal or no liming. Very low pH delays nutrients uptake by plants and therefore plant metabolism. Levels of total soluble salts, Mg²⁺, Ca²⁺, Na⁺ and K^- were within the acceptable limits for irrigation water. Salinity of water was low and ranged from 0.00 to 0.05 dsm^-1 with EC from 64.30 to 104.50 μmhos which falls below the upper limit of standard for irrigation water (2,000 μmhos). Total suspended solids concentrations were from 9.00 to 13.00 mgl^-1 . These ranges are relatively low to medium compared to the standard limits and may pose no harm or threat to plants irrigated or cause damage to pumps if screens are not used to exclude them. The anions: NO₃^-, HCO₃^-, CO₃^2-, Cl^- SO₄^2- levels were however less than the upper limit for irrigation water. Therefore, the waters were highly suitable for irrigation without improvement. Trace elements were 0.44 to 0.93 mgl^-1 for Fe, 0.03 to 0.12 mgl^-1 for Mn, 10.00 to 14.00 mgl^-1 for Cd, 3.00 to 5.00 mgl^-1 for Pb and 0.25 to 0.45 mgl^-1 for B (maximum application rates should not exceed that which allows normal crop growth as plant uptake is so small). In general terms therefore, qualities of irrigation water in the study sites conformed to the specifications for irrigation water.

Keywords
Suitability; evaluation; Sources of Irrigation Water; Major Rivers; Mid-Benue Trough