Growth and physiology of deciduous shade trees in response to controlled-release fertilizer

Abstract

Managing tree nutrition is a major consideration in container production to optimize growth while minimizing potential nutrient leaching. In this study, we examined growth and physiological responses of deciduous shade trees grown in a pot-in-pot container production system to controlled-release fertilizer (CRF). In May 2006, we potted twenty 2.5–3.0cm caliper bare root liners of Acer×freemanii ‘Jeffersred’, Acer rubrum ‘Franksred’, Liriodendron tulipifera, Platanus×acerifolia ‘Bloodgood’, Quercus rubra, Ulmus japonica×wilsoniana ‘Morton’, and Ulmus ‘Morton Glossy’ in 95-L (25-gal) containers. Treatments consisted of controlled-release fertilizer (15-9-12; N-P2O5-K2O, 8–9 month release) top-dressed at rates of 15, 30, 45, and 60gNtree−1 for the 2006 growing season, and 19, 38, 56, and 75gNtree−1 for the 2007 growing season. Tree height and caliper growth increased with each fertilizer increment in 2006. In 2007, maximum tree height and caliper growth occurred at 56gNtree−1. Total leaf area production increased in proportion to fertilizer addition, which supports the hypothesis that fertilizer increases growth by increasing total leaf area per tree. Photosynthetic response to fertilizer rate varied by species. In 2007, trees of most species had lowest photosynthetic rates at 56 or 75gNtree−1, possibly as a result of increased water stress associated with greater total leaf area. In 2007, chlorophyll content index was highly correlated with foliar N concentration, which may be useful in detecting nutrient deficiencies, although the relationship was species dependent.