Arboriculture & Urban Forestry 33(2): March 2007 119 negligible and 1 to 3 months into the growing season after transplant (depending on species) (Harris et al. 1995, 1996). It is unclear whether practitioners can reasonably expect to provide sufficient fertilizer to transplantedB&B trees through traditional methods and rates. We suggest that further study is merited using higher application rates or other meth- ods (such as foliar application or nutrient loading during nurs- ery production). There is evidence that nutrient loading of container-grown trees at the nursery before harvest can affect growth rates of transplanted trees during the first year (Lloyd et al. 2006). The importance of nitrogen reserves to growth is also apparent in several other studies. In apple trees, reserve nitrogen was found to be a more important determinant of spring shoot flushes than reserve carbohydrates (Cheng and Fuchigami 2002). Dyckmans and Flessa (2001) studied ni- trogen mobilization in young beech trees growing in washed sand (labeled N was provided through nutrient solutions) and concluded that internal nitrogen stores, rather than current supply, had the strongest influence on growth. In the case of B&Btrees, the degree to which nutrient loading might be offset by the loss of much of the root system would also need study. CONCLUSIONS Currently, standards recommend slow-release fertilizer for new transplants and rates comparable to those used in this study. It may be that using nutrients to enhance rapid estab- lishment ofB&B trees can be achieved by other means (different rates, timing of application, or nutrient loading). Current recommendations, however, did not speed establish- ment for the species studied here. Soil nutrient supply may also be a factor. Although the study site has relatively poor native nitrogen availability as is typical of many urban sites in the mid-Atlantic region of the United States, it is not se- verely compacted or scraped. There are many sites with more extreme soil conditions—such as disturbed sites where the A (and sometimes B) soil horizons have been removed. Two experiments in progress will examine fertilization at higher rates in soils disturbed by building construction to determine if fertilization can achieve the goal of speeding establishment under these more extreme conditions. At present, however, it appears that other site treatments such as improving overall soil conditions by adding organic matter and reducing com- paction (Day et al. 1995) and increasing soil volume (Grabosky and Gilman 2004) may be the most worthwhile investments to speed establishment and long-term growth. Unfortunately, these treatments tend to be more expensive and require planning and coordination, which are often dif- ficult to obtain in urban environments. Our findings from the current study indicate: 1. Current fertilizer rate recommendations do not speed establishment ofB&Bred maple and littleleaf linden in moderately poor soil conditions. 2. Fall applications of fertilizer are not more effective than spring applications for red maple and littleleaf linden in these conditions. No fertilization regime improved growth, however, so differences may not be apparent. 3. There was no evidence that fertilizer treatments had negative effects on the growth of unirrigated littleleaf lindens and red maples when compared with irrigated trees, even when rainfall was below average. IMPLICATIONS FOR ARBORICULTURE Research concerning fertilization at planting of balled-and- burlapped trees still has not provided definitive answers, and the arboriculture profession should expect recommendations to change as more information becomes available. Fertilizing B & B trees does not speed establishment under average to moderately poor landscape conditions for littleleaf linden and red maple, whether irrigated or not, in the soil conditions described in this experiment. There may be situations in which fertilization at this time is beneficial, but these have not been fully defined. The results of this study do not pro- vide evidence that fall transplanting is more effective than spring transplanting. Our research further did not suggest that fertilization at transplanting or fertilization of unirrigated trees during establishment will result in tree stress. Acknowledgments. This research was funded in part by the TREE Fund John Z. Duling Grant Program. We are grateful for this support and for the invaluable technical assistance of Jody Fanelli and John James at the Urban Horticulture Center of Virginia Tech. We are also grateful to Dr. Dan Ward (former Statistician for the Virginia–Maryland Regional College of Veterinary Medicine, currently Assistant Professor of Horticulture at Rutgers University) for statistical consultation. LITERATURE CITED Aguirre, P.B., Y.K. Al-Hinai, T.R. Roper, and A.R. Krueger. 2001. Apple tree rootstock and fertilizer application tim- ing affect nitrogen uptake. HortScience 36:1202–1205. American National Standards Institute (ANSI). 1998. ANSI A300 (Part 2) for Tree Care Operations—Tree, Shrub and Other Woody Plant Maintenance–Standard Practices. American National Standards Institute, New York, NY. ———. 2004. ANSI Z60.1 American Standard for Nursery Stock. American Nursery and Landscape Association. Cassman, K.G., A. Dobermann, and D.T. Walters. 2002. Agroecosystems, nitrogen-use efficiency and nitrogen management. Ambio 31:132–140. Chacalo, A. 2000. AREA Forum: Why fertilize trees in the urban landscape? Journal of Arboriculture 26:230–232. Cheng, L., and L.H. Fuchigami. 2002. Growth of young apple trees in relation to reserve nitrogen and carbohydrates. Tree Physiology 22:1297–1303. ©2007 International Society of Arboriculture
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