AMF inoculation positively regulates soil microbial activity and drought tolerance of oat

Objectives We studied the effects of arbuscular mycorrhizal fungi (AMF) inoculation on soil microbial properties and soil nutrient availability under drought stress, to provide a mycorrhizal regulation technology to enhance the drought resistance of oat in dryland areas.

Methods Pot experiments were conducted for two years, using the mixture of calcareous cinnamon soil and river sand at a ratio of 3 to 1 as cultural substrates (adding N 0.315 g and P₂O₅ 0.087 g per pot). The soil relative water content (RWC) of 75% and 55% of field water capacity and inoculating with and without AMF (Rhizophagus intraradices) composed four treatments. At the heading stage of oats, the soil microbial characters, nutrient contents were analyzed. The nitrogen (N) and phosphorus (P) accumulation in various parts of oat plant, and the grain yield were recorded at maturity stage.

Results The AMF infecting rate in oat roots under 55%RWC was 23.28%−33.35% lower than that under 75%RWC with AMF inoculation. Drought stress significantly reduced the soil microbial biomass, enzyme activities, available N and P; and increased the soil pH and organic carbon. AMF inoculation under drought stress significantly increased MBC, MBN, MBP, and invertase, urease and alkaline phosphatase activities, significantly increased the available P by 4.92%−5.41%, but did not change soil organic carbon and pH. Further, the N and P accumulation in oat root, stem, leaf, and ear were significantly increased, and grain yield was significantly increased by 14.20%−14.74%. AMF inoculation, soil pH and available P was the main factors affecting soil microbial characters; Soil MBN and urease activity were the main factors affecting soil nutrients; available P was the main factor benefitting oat plants.

Conclusions AMF inoculation under drought stress increased the infection rate of AMF in oat roots, enhanced the microbial mass and enzyme activities, mobilized more P in rhizosphere soil, thus increased the N and P accumulation in various parts of the oat plant and oat grain yield. Therefore, AMF inoculation is an effective way to enhance the drought resistance of oat.