Foliar Absorption of Nitrogen by Creeping Bentgrass Putting Green Turf Utilizing Select 15N−labeled Inorganic and Organic Sources.

Foliar nitrogen (N) fertilization often comprises a major portion of the total N inputs applied to creeping bentgrass golf greens annually.  Many of these applications are made using fertilizers that have been formulated and marketed as specialty foliar fertilizers.  Various forms of inorganic and organic N are usually included in these products purchased by golf course superintendents.  However, little is currently known about the foliar absorption efficiency among different chemical N forms routinely applied to putting greens.  This project was conducted to evaluate foliar uptake of N after application of different ¹⁵N-labeled inorganic and organic sources.  Three common N fertilizer forms [(urea, ammonium sulfate ((NH₄)₂SO₄), and potassium nitrate (KNO₃)] were used in the trial, along with three amino acids (glycine, glutamic acid, and proline).  All treatments were applied at a rate of 0.5 g N m^-2 on 18 September 2008 to plots within a ‘Penn G2’ creeping bentgrass research green.  Plant tissue samples were taken 1 h and 8 h after application for N analysis.  Foliar uptake of the various N compounds ranged from 37 - 56 % of the N applied at the final sampling time of 8 h after application.  Nitrogen source had a significant effect on the amount of fertilizer N recovered within plant leaves/shoots.  Absorption of KNO₃ into aerial plant parts was significantly lower than all of the chemical forms tested, while the other treatments were taken up similarly.