Relationships between manganese content of oats grown at eight experimental centres and the water-soluble manganese and total manganese of the soil have been investigated. Uptake of manganese by the plant correlates highly significantly with water-soluble manganese of soil at each of eight centres. Regression equations of the form y=a+bx have been calculated for each centre, where y=manganese content of the plant and x=water-soluble manganese of the soil. The value of the constant term a is shown to be roughly proportional to the total manganese content of the soil. The coefficients of x are found to vary from one centre to another, so that differing uptakes may be expected at different centres from plots having the same level of watersoluble managanese. The significance of these findings is discussed.