Effects of N, P, and K on formation of vesicular-arbuscular mycorrhizae, growth and mineral content of onion

Abstract

The effects of N, P, K and the vesicular-arbuscular mycorrhizal fungusGigaspora calospora (Nicol. and Gerd.) Gerdemann and Trappe on root colonization, spore production, dry biomass and shoot mineral content of onion (Allium cepa L. cv. Autumn spice) were investigated. All combinations of presence or absence of N, P, K and inoculum were tested. Nitrogen fertilization stimulates root colonization, and spore production is higher on plants fertilized with K. Phosphorus fertilization reduces root colonization and spore production. Biomass of endomycorrhizal plants is higher than that of non-mycorrhizal plants. Yield increases due to P are larger when plants are not fertilized with additional N. When plants are fertilized with either N, P or K they absorb more N, P or K, respectively. Some interactions between N, P, and K have an effect on tissue P and Ca content. Optimal ratio of available nutrients in the soil is essential for the host plant-VAM fungus system to be most efficient.