Physiological Aspects of the Supplementary Foliar Application of P in Intensive Cereal Growing

Summary

Because of the enormous increase in cereal yield, the plants’ requirements for a consistently high supply of P, particularly in the critical stages of growth, have also increased. A satisfactory supply of P throughout the vegetative stage of growth is clearly necessary. Possible physiological reasons are enumerated and discussed with reference to the literature. Spraying trials with radio-labelled P foliar fertilizer were therefore conducted with the aim of determining at harvest, the distribution and part played by the phosphate supplied via the leaves. The results show that the tendency of both low and high concentrations of phosphate in the spray solution, to be stored largely in the seed, was the same: at harvest, approx. 65 – 70% was in the seed, approx. 20 – 25% in the straw and 10% in the chaff. The foliar sprays that had been applied at various stages in the development of the wheat following the formation of the last flag leaf had no significant effect on the absorption and distribution of P at grain ripeness. In fact only a very high P concentration in the foliar fertilizer solution produced an 8 – 13% increase in the P content of the seed. Foliar fertilizers with a reasonably high but plant-acceptable P content should therefore be developed.