Influence of Leaf Cuticular Wax Amount and Composition On Foliar-Applied Nitrogen Absorption by Creeping Bentgrass.

Golf course superintendents commonly use foliar fertilization methods to supply a significant portion of the total annual nitrogen (N) needs of putting green turfgrasses; however, little is currently known about the efficiency of this practice in the field or factors that may affect it.  Previous research exploring foliar uptake of N by leaves of agricultural and horticulture crops has attributed reductions in fertilizer absorption efficiency with changes in leaf cuticle wax amounts and/or chemical composition.  This study was conducted to examine the possibility of a similar phenomenon affecting foliar fertilizer uptake on golf course putting greens.  Foliar fertilizer treatments of ¹⁵N-labeled urea were applied once a month (May through September) in 2007 and 2008 to creeping bentgrass (Agrostis stolonifera var. palustris (Huds.) Farw. cv. ‘Penn A1’).  Fertilizer uptake efficiency was quantified through direct measurement and, prior to treatment applications, samples were also taken to assess leaf cuticle characteristics.  Hexane-extractable wax loads and cuticle wax chemical composition were determined via gravimetric and gas chromatographic analysis, respectively.  Leaf cuticle wax loads were affected by month and year.  Regression analysis indicated a significant negative relationship between creeping bentgrass foliar N fertilizer absorption efficiency and leaf cuticle wax amounts, but this relationship was relatively weak (r² = 0.34).  Creeping bentgrass leaf cuticle wax compositional analysis revealed that a long-chain (C₂₆) primary alcohol (1-hexacosanol) consistently comprised around 90 % of the total abundance.  Variability in foliar N uptake efficiency on creeping bentgrass was not fully explained by leaf cuticle wax amounts or 1-hexacosanol content.