Effects of arbuscular mycorrhizal fungi and earthworms on plant-soil systems of urban turf grasses

Background Arbuscular mycorrhizal fungi (AMF) and earthworms have been known to enhance plant growth and improve soil quality, but the results have shown some inconsistencies, exhibiting synergistic or independent effects under different studies. Methods In this study, we conducted a factorial experiment to investigate the effects of arbuscular mycorrhizal fungi and earthworms, both individually and in combination, on plant-soil systems of urban turf grasses. Five turf grass species of different functional groups (gramineous and leguminous) were inoculated with AMF ( Glomus mosseae ) and earthworms ( Pheretima tschiliensis Michaelsen, 1928) in a pot culture experiment, and we comprehensively assessed the eco-physiological properties of both the plant and the soil. Results Inoculation with AMF and earthworms promoted the growth of five turf grass species. Specifically, AMF had a greater impact on the height and biomass of leguminous plants (white clover and alfalfa) compared to gramineous plants (ryegrass, early meadow grass, and tall fescue), while the effects of earthworms on two functional groups were opposite to those of AMF. AMF and earthworms had different dimensions of effects on the physical and chemical properties of the soil compared to the control, with AMF showing a better improvement in soil quality than earthworms. The results indicated that effects of AMF and earthworms on urban turf grasses and soil were dependent on different species. Dual inoculation with AMF and earthworms showed positive effects exclusively on the soil properties of five turf grass species, but only positive on the growth of gramineous plants. The comprehensive evaluation indicated that dual inoculation with AMF and earthworms did not improve the plant-soil system more effectively than AMF alone. Conversely, gramineous plants inoculated with AMF showed the greatest effective improvement in the soil-plant system. Therefore, dual inoculation with AMF and earthworms did not have a more positive effect on plant-soil system than that could be expected from the effect of single inoculation of either AMF or earthworms. Further analysis showed that AMF exhibited the most comprehensive improvements in the plant-soil system of gramineous plants, indicating that the effects of AMF and earthworms on the soil-plant system of lawn might be influenced by the specific plant species.