Fertilizer Applications for Container-Grown Ornamental Tree Production

Abstract

Better management of nutrient applications during a growing season is needed to economically produce marketable container-grown ornamental shade trees. Fertilizer practices were used to test the growth of Acer rubrum ‘Red Sunset’ trees in two commercial nursery fields (each containing four plots) that were irrigated with either city or pond water. In each field, the same 16 treatments were replicated. Two slow-release granular fertilizers (18-5-12 and 12-0-42) were applied separately or together by incorporation, topdress or both to a potting mix for trees grown in 26 liter (7 gal) containers and placed above or below ground. Trees irrigated with pond water also received supplemental liquid nutrients throughout the growing season along with nitric acid to lower the pH of the potting substrate. Tree growth was assessed by stem diameter (caliper), height, canopy size, leaf color and root measurements. Significant higher caliper increases occurred in trees treated with 18-5-12 fertilizer and irrigated with either pond or city water than trees treated with the 12-0-42 fertilizer. Significantly higher percent increases in caliper also occurred for trees irrigated with pond water and top-dressed with 18-5-12 fertilizer than trees with incorporated 18-5-12 fertilizer. With the same slow-release fertilizer applications, trees irrigated with pond water and supplemental nutrients had greater percent increases of caliper, larger canopy areas and better root systems than trees irrigated with city water. The differences in tree height increase were not as great as the caliper increases. However, tree growth irrigated with pond water required additional inputs with extra nutrients and labor costs throughout the growing season.