Effect of Cu and Mo on Cu/Mo ratio and their concentration in different organs of cowpeas (Vigna sinensis L.)

In a Typic Torripsamments (loamy sand) soil, 4 levels each of Cu and Mo,viz, 0, 5, 10 and 20; and 0, 0.5, 1.0 and 2.0 ppm, respectively, were added to study Cu−Mo relationship in cowpeas in a screen-house. Application of Mo reduced Cu content andvice versa in leaves, stems and roots of cowpeas. Stems accumulated more of Mo and Cu than leaves and roots, showing thereby, that it might be the site of interaction for Mo and Cu. Molybdenum increased to a toxic level in plant (for animals) following its application. Cu/Mo ratio was narrowed with Mo and widened with Cu addition. It was either more than 2∶1 or less which suggested that Mo would cause Cu deficiency and Cu in the absence of Mo would be toxic to ruminants.