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

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 2.5–3.0 cm 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 60 g N tree−1 for the 2006 growing season, and 19, 38, 56, and 75 g N tree−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 56 g N tree−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 75 g N tree−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.

► We examined growth and physiology of 7 tree taxa in response to fertilization.
► Within taxa, growth rates increased in proportion to leaf area accretion.
► In year 2, gas exchange decreased at the highest fertilizer levels.
► Chlorophyll index was correlated with foliar N, but response was taxa-specific.