The influence of chemical forms on foliar-applied nitrogen absorption for peach trees

To determine the most effective chemical form of foliar nitrogen (N) application for peach trees, we compared various kinds of foliar-applied N and determined N absorption into the leaf. In the first experiment, N-15 labeled 50mM solutions were sprayed on to peach leaves in a greenhouse and the amounts of absorbed N were determined using a mass spectrometer. Absorption rates were the highest from urea and sodium nitrate, followed by ammonium chloride and four amino acids, namely L-alanine, L-glutamic acid, glycine and L-lysine, up to 7 days after foliar spraying. The total. amount of foliar-absorbed N showed a similar tendency to the foliar N absorption rate of 3-7 days after foliar spraying. In a subsequent experiment, 15 different amino acids were examined. The rate of foliar N absorption increased as the molecular weights of amino acids decreased. This relationship was not always found and the N absorption rate from arginine and L-lysine was significantly higher compared with other amino acids having the same molecular weights. Based upon these results, urea appeared to be the most effective fertilizer for foliar N application to peach trees compared with other inorganic N sources or amino acids.