Rhizoglomus intraradices Is More Prominent in Improving Soil Aggregate Distribution and Stability Than in Improving Plant Physiological Activities

Arbuscular mycorrhizal fungi (AMF) confer positive and negative effects on many plants, but it is unclear whether AMF has an effect on soil fertility, aggregate distribution, and stability. The aim of this study was to analyze the effects of Rhizoglomus intraradices on plant growth, root morphology, leaf chlorophyll and gas exchange, sugar concentrations, and soil nutrients, aggregate distribution, and stability in marigold (Tagetes erecta L.), maize (Zea mays L.), white clover (Trifolium repens L.), and vetch (Vicia villosa Roth.) plants. Twelve weeks after R. intraradices inoculation, maize presented the highest mycorrhizal development, while mycorrhizal dependence was shown to be the decreasing trend in marigold > white clover > vetch > maize. AMF inoculation significantly increased the chlorophyll index of marigold and white clover, the net photosynthetic rate of white clover, the stomatal conductance of maize and white clover, and the transpiration rate of maize. Fructose, glucose, and sucrose in the four plants were differentially affected by R. intraradices. R. intraradices significantly increased the soil organic carbon (SOC) of marigold, maize, and white clover, the Olsen-P of white clover, the available K content of marigold, the easily extractable glomalin-related soil protein (GRSP) of maize, and the difficultly extractable and total GRSP levels of marigold and vetch. In addition, R. intraradices significantly increased the stability of soil water-stable aggregates (WSAs) in all four plants, plus it increased WSA at 0.5–4 mm sizes. Root AMF colonization was significantly positively correlated with WSA stability, SOC, difficultly extractable GRSP, and total GRSP. It is concluded that AMF-triggered changes in plant growth, physiological activities, and soil fertility depended on plant species, but AMF-improved WSA distribution and stability were not dependent on plant species.