Photinia and Podocarpus Growth Response to a Hydrophilic Polymer-amended Medium

Abstract

Photinia ×fraseri Dress and Podocarpus macrophyllus (Thunb.) D. Don were grown in a Metro-Mix 500 medium amended with 0.0%,0.25%,0.5%,0.75%, or 1.0% (by volume) of a K-based hydrophilic polymer and were irrigated every 3,6,9, or 12 days with a solution that contained either 100, 200, 300, or 400 mg N/liter, respectively: Photinia ×fraseri plants irrigated every 6 days with 200 mg N/liter in irrigation water and grown in 0.75 % polymer-amended medium had higher root and shoot dry weights (6.3 and 28 g, respectively) after 144 days than plants grown in the unamended medium (3.4 and 17 g, respectively). Shoot dry weights of P. macrophyllus grown 192 days in the amended medium were similar to those of plants grown in the unamended medium. Average shoot dry weights increased from 10 to 18 g, respectively, as number of irrigations increased from every 12 days with 400 mg N/liter in irrigation water to every 3 days with 100 mg N/liter in irrigation water. Podocarpus macrophyllus root dry weights were 1.9 and 3.6 g for plants irrigated every 12 and 3 days, respectively, while plants grown in the unamended medium had the highest root dry weight (3.2 g). Data from this study indicated that growth response to a cross-linked, K polyacrylate/polyacrylamide, hydrophilic polymer-amended Metro-Mix 500 medium varied with species and number of irrigation and concomitant fertilizer applications.