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 15 N‐labeled inorganic and organic sources. Three common N fertilizer forms {urea (NH 2 CONH 2 ), ammonium sulfate [(NH 4 ) 2 SO 4 ], and potassium nitrate (KNO 3 )} 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 KNO 3 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.