Rhizosphere interactions between earthworms and arbuscular mycorrhizal fungi increase nutrient availability and plant growth in the desertification soils

Abstract

Earthworms (E) and arbuscular mycorrhizal fungi (AM) as the key components of belowground organisms can form highly complex interactions in soil food web. However, little is known about the direction and power of interactive effects on plant growth and soil fertility in nutrient-limited soils. The objectives aimed to explore the interaction of AM (Claroideoglomus etunicatum) and E (Amynthas divergens yunnanensis) and its effecting mechanism on the plant (Photinia fraseri Dress) growth and nutrient availability in the desertification soils in Karst area. A 2 × 2 factor block design was completely randomly arranged for the treatments in a pot experiment. The four treatments were no E and AM, E inoculation, AM inoculation and inoculations with both E and AM. We confirmed the hypotheses tested about a positive effect of combined inoculations and a more pronounced increase in the plant height (12.5–13.4%), base diameter (24–27%), root colonization (50%) and hyphal length density (312%) compared with separate inoculation. Whereas the inoculation with E or AM had an effect only on the plant height, and AM inoculation only on the hyphal length density. The combined inoculations resulted in a greater reduce in soil pH and a higher increase in soil organic matter and readily oxidizable organic carbon. The effect of combined inoculations on the growth of base diameter, root mycorrhizal colonization and hyphal length density was closely associated with the increase in soil organic matter and soil readily oxidizable organic carbon. In contrast, the effect of separate inoculation on plant height was related with the increase in pH, total nitrogen and phosphorus, plant available nitrogen and phosphorus in soils. Earthworms and AM fungi can create different nutritional niches for plants: E had greater increase in N availability, while AM fungi in P availability. Therefore, we conclude that the combined effects have a greater potential in increasing plant growth, through the complementary and interactive mechanisms of E and AM on modifying nutrient availability in the nutrient-poor soils in Karst stony desertification land.