Grass Competition for Nitrogen Around Landscape Trees

The sod around established saplings was treated with the nitrogenous fertilizer ammonium nitrate and/or the herbicide Roundup (glyphosate). Compared with untreated trees, all treatments increased the shoot growth of black walnut (Juglans nigra L.), and the trunk growth of sycamore (Platanus occidentalis L.), Norway maple (Acer platanoides L.), and honey-locust (Gleditsia triacanthos L. inermis Willd.). The response in walnut persisted for 2 growing seasons following application.