The effects of phosphate on early growth and maturity

A number of investigators have found that the use of phosphates produced a more rapid growth of the roots of seedlings and several have claimed that, in the case of small grains, phosphates promote tillering. Russell states that in England superphosphates cause rapid early growth of turnips and swedes. The evidence is not conclusive that these effects from phosphate are more pronounced than from the other fertilizer elements where the latter are the limiting factors for crop yields. Fertilizer tests have quite generally, if not always, shown that the use of phosphatic fertilizers induces earlier ripening of the grain crops on soils low in phosphorus. Similar effects have been noted with cabbage and with cotton. In the case of tomatoes, the use of phosphates at the Pennsylvania Experiment Station, has been accompanied by a much greater growth of stalk and larger total yield, but also by later ripening. The effects of different phosphatic fertilizers seem to vary with the availability of the phosphates as shown by the responses in crop yeilds. However, at the Ohio Experiment Station, acid phosphate had more influence in promoting earliness than either steamed bonemeal or basic slag, altho all these phosphates gave approximately the same yield. Applied in moderate rates, the soluble phosphates, as a rule, have shown a more pronounced influence in hastening maturity than the same quantity of phosphoric acid in rock phosphate, the influence in earliness varying in degree with the response in yield. Increasing the rates of application of phosphatic fertilizers above the needs of the crop as indicated by yields has not been accompanied by further increases in earliness. Though phosphates show a more marked influence in promoting earliness than the other fertilizer elements, yet moderate amounts of nitrogen and potash, where these are needed for the production of crops, have a similar effect. Lime, also, if applied to soils having a high lime requirement, may induce earlier ripening.