Effect of Wetting Agents upon Uptake by Sugarcane of Foliar-Applied Phosphorus

Abstract

The effect of wetting agents at three different concentrations upon the absorption of foliar-applied phosphates was studied. A concentration of 0.1 percent of the wetting agent proved to be the best to work with, for it gave the maximum phosphate absorption in all cases. The order of their effectiveness, as measured by the ability to enhance phosphorus absorption by the leaf was as follows: Tergitol 7 > Sterox AJ-100 > Agricultural surfactant > Atlox 210 > Triton X-400 > Atlox 209 > Glycerine. Both Tergitol and Sterox AJ-100 increased in phosphorus absorption while glycerine caused a reduction in absorption when applied as sprays (14,19). The maximum absorption by sugarcane leaves of foliar-applied orthophosphates of sodium, potassium, and ammonium was found to occur at pH's 5, 3, and 10, respectively. As pointed out in the literature (19) phosphate absorption varies with the accompanying cation, the pH of the applied solution and the time the applied solution is in contact with the leaf. The time required for 50-percent absorption of potassium orthophosphate by the leaf of a 1-month-old sugarcane plant was 18 days. Burr et al. (8) report 15 days as the comparative absorption rate for sugarcane.