Colloidal Silica and the Efficiency of Phosphates

General fertilizer practice recognizes in a vague way that there are reactions between soils and phosphatic fertilizers which affect the efficiency of the fertilizers. Bone meal, for instance, is recommended for use on open soils which are not too dry (39, p. 169), and for light soils not too deficient in phosphoric acid (3%, p. 320). Floats are recommended by Wheeler (39, p. 173) for acid soils high in organic matter, and by Schneidewind {82, p. 321) for acid high-moor soils but not for mineral soils. Acid phosphate, according to Schneidewind (32, p. 297), is adapted to all the ''better" and heavier soils. However, the extent to which a phosphate is dependent on the character of a soil is probably not sufficiently appreciated.