Effects of Fertilization and Vesicular-Arbuscular Mycorrhizal Inoculation on Growth of Hardwood Seedlings

Eight hardwood species were grown in fumigated soil without vesicular-arbuscular mycorrhizae (VAM) or in soil infested with a mixture of Glomus mosseae and Glomus etunicatus. Three fertilizer treatments of 140, 560, and 1,120 kg/ha of 10-10-10 fertilizer were established in combination with the two mycorrhizal treatments. Ten equal applications of NH4NO3, totaling 1,680 kg/ha, were added to all the treatment plots during the growing season. For six of the eight species, the VAM seedlings showed greater height and diameter growth and dry weight production than nonmycorrhizal seedlings. Sugar maple (Acer saccharum Marsh.) and walnut (Juglans nigra L.) displayed no height growth differences. Only boxelder (Acer negundo L.), of the inoculated seedlings, consistently responded to increases in fertilizer level. Nonmycorrhizal seedlings generally showed increased growth with increased fertilizer applications. The growth of the nonmycorrhizal seedlings at the higher fertilizer levels was not sufficient to produce plantable seedlings for artificial regeneration. A difference in host preference for the Glomus spp. symbionts is suggested by the large difference in infection between species. Infection values varied from a high of about 80% for sycamore (Platanus occidentalis L.), green ash (Fraxinus pennsylvanicaMarsh.), and boxelder to a low of 40% for sugar maple and sweetgum. The growth data suggest that high quality seedling stock of most of these hardwood tree species can be obtained in nurseries as long as cultural practices in the nursery encourage VAM development.