Performance of seedling and mixed-species planting test of three species of Rubiaceae treated by different seedling media and mycorrhizae application

Abstract

Seedling growth in the nursery and early field performance of three fast-growing tree species from the Rubiaceae family, i.e., white jabon (Neolamarckia cadamba), red jabon (Neolamarckia macrophylla, and gempol (Nauclea orientalis), were tested by using different seedling media and arbuscular mycorrhizal fungi (AMF) treatments in the nursery and mixed-species field tests. The experiment design in the nursery and field test was laid out following a split-split plot design of a randomized complete block with four replications. The main factors were tree species, the sub-factors were seedling media, and the sub-sub factors consisted of the AMF inoculation, with a mixed species planting pattern. White jabon had a more dominant growth both at the seedling level in the nursery and at the field test level until the age of 2 years, followed by gempol and red jabon. AMF inoculation in those three species at the seedling level was strongly influenced by the characteristics of the seedling media like media with high fertility levels resulting in a very low percentage of AMF colonization. In the field trial, all tree species and treatments were infected with mycorrhizae with colonization percentages ranging from 27.6% to 57.7%, which was suspected to be an infection from native AMF in the planting site. The AMF application had a significant effect on the percentage of colonization and tree diameter growth of 2-year-olds with a percentage increase of 14.4% and 8.4%, respectively.