Perennial Ryegrass Growth Responses to Mycorrhizal Infection and Humic Acid Treatments

Arbuscular mycorrhizal (AM) symbiosis confers numerous benefits to host plants, including improved plant growth and nutrient acquisition efficiency. An experiment was conducted to evaluate the effect of AM fungi (Glomus intraradices and G. mosseae) in the presence of humic acid (HA) spray treatments (0, 100, 400, and 1000 mg L-1) on nutrient (N, P, K, Fe, and Zn) uptake, visual quality and chlorophyll content, root growth and architecture, and colonization of perennial ryegrass (Lolium perenne L.) Speedygreen mixture. The results revealed that HA did not affect plant growth significantly; instead arbuscular mycorrhizal fungal (AMF) colonization improved dry and fresh weights. Mycorrhizal inoculations significantly increased visual quality (13 and 15% in inoculated plants compared to non-inoculated ones) that might be at least partly due to elevated total chlorophyll content. The AM inoculation and HA treatment resulted in improved root architecture rather than root biomass production. Neither HA treatments nor mycorrhizal inoculation affected N and Fe contents of the leaves; however P, K, and Zn concentrations improved by AM inoculation. More roots were colonized by G. intraradices than by G. mosseae. These results suggest that AM inoculation is beneficial in enhancing uptake of some nutrients and root development of ryegrass possibly leading to less fertilizer input and more drought resistance.