Impact of Fertilizers on Ornamental Nursery Plant Growth and Mycorrhizal Colonization.

Red oak, azalea, and Thuja plants were inoculated with naturally-occurring ecto-, ericoid, and arbuscular mycorrhizal fungi, respectively, using soil inocula. Plants were grown in #3 containers containing a formulated mix of pine bark, peat moss, sand (80:10:10) and amended with 5% calcined clay particle size 5/20. Plants were fertilized with Osmocote 17-5-11, Nutricote Total 17-7-8, and Polyon 17-6-12 to supply 9.52 g N and compared to non-inocualted plants arranged in a RCBDesign.  Plant top and root biomass, percent root colonization by mycorrhizal fungi. While there was no significant increase in top biomass of inoculated azalea and Thuja plants in comparison to non-inoculated, a significant increase in top biomass was observed in inoculated red oak plants in all fertilized treatments. Similarly, root biomass increased significantly in inoculated red oak plants while root biomass was slightly, but not significantly, reduced in inoculated azalea and Thuja plants. Percent root colonization of red oak with ectomycorrhizal fungi increased in plants treated with either Nutricote Total or Polyon, providing higher diversity and greater chances of success in outplanting. Significant and higher percent hyphal colonization of ericoid mycorrhizal fungi in azalea roots was observed in Nutricote Total treated plants in comparison to non-inoculated plants. The reduction in root biomass of inoculated Thuja plants and treated in Nutricote Total and Polyon treatments could be explained by the increase in percent hyphal, arbuscules, and spore colonization of Thuja roots, increasing nutrient uptake by the plants.