Foliar Absorption of Various Inorganic and Organic Nitrogen Sources by Creeping Bentgrass

Foliar N fertilization often makes up a major portion of the total N inputs applied to creeping bentgrass (Agrostis stolonifera L.) golf greens. Many such applications are made using fertilizers that have been formulated and marketed as specialty foliar fertilizers. Various forms of inorganic and organic N are included in these specialty products. 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 the foliar uptake of N from several N-15-labeled inorganic and organic sources. Three common N fertilizer forms {urea (NH2CONH2), ammonium sulfate [(NH4)(2)SO4], and potassium nitrate (KNO3)} were used in the trial along with three amino acids (glycine, L-glutamic acid, and L-proline). All treatments were applied at a rate of 0.5 g N m(-2) on 18 Sept. 2008, 14 Oct. 2008, and 24 June 2010 to plots within a ` Penn G2' creeping bentgrass research green. Plant tissue samples were taken 1 and 8 h after application for N analysis. Foliar uptake of the various N compounds ranged from 31 to 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 N fertilizer recovered within plant leaves and shoots. Foliar absorption of KNO3 into aerial plant parts was lower than most of the chemical forms tested while most of the compounds supplied N to the plant in similar proportions.