Turf Fertilization Effects on Seasonal Nitrogen Levels of Autumn Blaze™ Maple and Kentucky Bluegrass in a Mixed Urban Landscape

It is commonly assumed that trees growing in a lawn receive sufficient nitrogen (N) from lawn fertilization. However, few researchers have examined the effect of N lawn fertilization on N levels of trees growing in urban landscapes. In this study, we applied nitrogen at a rate of 0 or 293 kg N per hectare (0 or 6 pounds N per 1000 square feet) to separate medians containing Kentucky bluegrass (Poa pratensis L.; KBG) turf and monostands of 15 year-old Autumn Blaze^TM maples (Acer xfreemanii ‘Jeffersred’; ABM). The purpose of this study was to determine the relative amounts of N assimilated by KBG and ABM throughout the growing season following spring and summer N applications. Nitrogen was applied in April and June 2013 [sic] using a 35N–0P–8.3K fertilizer (28.35% urea nitrogen from polymer-coated urea) at a rate of 146 kg N per ha (3 pounds N per 1000 square feet) at each application. Grass clipping and tree leaf samples were collected biweekly (June–September), dried, ground, and analyzed for total N. Leaves were collected on a monthly basis from single branches and used (via the pipe stem model) to estimate total tree dry leaf weight.