Growth Response of Container-grown Pin Oak and Japanese Maple Seedlings to Sulfur Fertilization

Abstract

Sulfur (S) is essential to the growth of higher plants; however, research on S fertilizer requirements for container-grown nursery tree species has not been established. The purpose of this study was to determine the substrate solution S concentration that maximizes the growth of container-grown pin oak (Quercus palustris Münchh) (pin oak–K2SO4 experiment) and japanese maple (Acer palmatum Thunb.) (japanese maple–K2SO4 experiment) in a pine bark (PB) substrate. Both species were fertilized with solutions supplying a range of S concentrations (0, 1, 2, 5, 10, 20, 40, or 80 mg·L–1) using K2SO4. Regression analysis revealed that dry weights of both species were near maximum at the predicted application concentration of 30 mg·L–1 S, which corresponded to about 15 and 7 mg·L–1 S in substrate solution for pin oak and japanese maple, respectively. In a Micromax, FeSO4, lime experiment, S was supplied to pin oak via a preplant micronutrient sulfate fertilizer or FeSO4 in limed or unlimed PB. When the PB pH was relatively low (4.5, unlimed), FeSO4 and the preplant micronutrient fertilizer were effective in supplying ample S. However, when the PB pH was relatively high (6.1, limed), the preplant micronutrient fertilizer with micronutrients in a sulfate form was more effective in supplying S and micronutrients than FeSO4.