Table of Contents L.P. Werner and L.G. Jull Fertilizer Uptake, Partitioning, and Recovery in Container- Grown Common Hackberry (Celtis occidentalis) Trees ............................................................................................................. 252 N partitioning, and aboveground N status in container-grown common hackberry (Celtis occidentalis L.) trees back-filled with native soil at Arlington, Wisconsin and Lisle, Illinois, U.S. Treatments consisted of 0, 1.42 g N tree-1 the area equivalent of 0, 0.49, and 1.47 kg N 100 m-2 Abstract. Ammonium-nitrate (NH4NO3) double enriched with the 15 N isotope (1.5 atom %) was used to evaluate fertilizer N recovery, (0.05 oz) and 4.27 g N tree-1 (0, 1, and 3 lb N 1000 ft-2 fertilization. Fertilizer-induced changes in aboveground N status were significant only at the 4.27 g N tree-1 (0.15 oz), ). Trees were harvested 14, 30, 60, and 90 days after (0.15 oz) treatment level. The amount of fertilizer N recovered in aboveground tissues increased with rate of application. Fertilizer N was preferentially partitioned to foliage and current season stem wood. The percentage of fertilizer recovered in aboveground tissues did not differ between the application rates, ranging from 15%–25% at Arlington, WI, and 5%–9% at Lisle, IL. Frost damage to the foliage at Lisle, IL may have resulted in location differences in aboveground biomass which affected fertilizer N uptake and recovery. These data suggest fertilizer N accumulated in nontarget sinks and/or were lost from the site of application at both rates of application. Key Words. ANSI A-300; Fertilization; Landscape Trees; 15 N. Glynn C. Percival and Ian Haynes The Influence of Calcium Sprays to Reduce Fungicide Inputs Against Apple Scab [Venturia inaequalis (Cooke) G. Wint.] .......................................................................................... 263 Abstract. A goal of pathogen management in the arboriculture industry should be to eliminate or reduce the amount of active ingredients of synthetic fungicides used within a growing season. The aim of this research paper was to evaluate a nonfungicidal pathogen management sys- tem by investigating the hypothesis that replacing an apple scab fungicide spray program with calcium reduces fruit and leaf scab severity. In addition, a separate study investigated if a relationship existed between calcium concentrations within foliar tissue of resistant, intermediate, and sensitive apple species and varieties toward scab infection. A number of commercially available calcium products were applied to apple cv. Crown Gold trees at four distinct growth stages (bud break, 90% petal fall, early fruitlet, two weeks aſter early fruitlet). A comparative evalu- ation of the synthetic fungicide penconazole commercially used for scab control was also conducted. The experiment was performed in 2006 and repeated in 2007 at the University of Reading Experimental Field Site (UK). Application of calcium sprays significantly reduced the leaf and fruit scab severity of apple cv. Crown Gold however; in a separate study no relationship existed between foliar calcium content and suscep- tibility to apple scab attack between resistant, intermediate, and sensitive Malus species. Greatest protection in both field trials was provided by the synthetic fungicide penconazole. Within the calcium products evaluated, greatest protection in both field trials was provided by calcium chloride and calcium hydroxide. The integration of calcium foliar sprays into existing scab management practices offers a useful addition to reduce scab severity on ornamental apples that has applicability against other foliar diseases frequently encountered within urban landscapes. Key Words. Fruit; Holistic Approach; Integrated Disease Management; Pathogen Control; Plant Health Care; Urban Landscapes. Jason Grabosky, Edward Haffner, and Nina Bassuk Plant Available Moisture in Stone-soil Media for Use Under Pavement While Allowing Urban Tree Root Growth ......................................................................................................................... 271 Abstract. Three avenues of experimental observation detail aspects of plant available water holding capacity in compacted stone-soil media designed for urban tree establishment in paved situations. The various compacted media provided an estimated plant available moisture content of 7%–11% by volume, comparable to a loamy sand. Changes in aggregate and of soil influenced initial field capacity moisture content, but high matric potential moisture content was consistent, presumably as a reflection of the aggregate content of the designed system. A large portion of plant available moisture was weakly held in large voids, consistent with related infiltration and permeability data, and could be an influence in water storage and irrigation planning to use layers of designed soils in a layered pavement section for urban vegetation. Key Words. Stalite; Structural Soil; Plant Available Moisture. ©2009 | International Society of Arboriculture | ISSN:1935-5297
September 2009
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