Fertilizer Application Method Affects Growth, Nutrient, and Water Use Efficiency of Container-Grown Shade Tree Whips

Abstract

The mineral nutrition requirements and fertilizer application methods for container-grown shade tree whips are not well understood. This experiment was conducted to determine the effects of fertility method (water soluble vs. controlled release) on growth, water, and N use efficiency of four taxa [(Acer ×freemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus (Mill.), `Prairifire' (Prairifire crabapple), and Quercus rubra L. (red oak)] in two production environments [outdoor gravel pad vs. a retractable roof structure (RRS)]. No single fertilizer method consistently resulted in the greatest growth. In the RRS, maple and crabapple heights, and crabapple and redbud caliper were larger when whips were fertilized with controlled-release fertilizer (CRF); outdoors, CRF resulted in taller maples and larger caliper crabapples. However, in the RRS, maple whips fertilized with water-soluble fertilizer had higher production water use efficiency than those fertilized with CRF, whereas crabapple whips had higher N use efficiency when fertilized with CRF. Nitrogen use efficiency was higher for redbud and crabapple whips fertilized with CRF than with CRF. Outside, crabapple whips fertilized with CRF had higher production water use efficiency than those fertilized with water-soluble fertilizer. There were no differences in N use efficiency attributed to fertilizer method. When averaged over fertilizer application methods, height, caliper, water, and N use efficiency were greater when whips were grown in RRS than outdoors. There were two exceptions: Maple caliper and production water use efficiency were marginally higher when whips were grown outdoors. The greater growth for whips produced in the RRS was attributed to reduced ambient and substrate temperature stress.