On-farm produced microbial soil inoculant effects on bread wheat (Triticum aestivum) production

The use of microbial soil inoculants in agriculture is of increasing interest among growers and scientists. This study aimed to determine the effects of a commercially available arbuscular mycorrhizal fungus (AMF) inoculant, an on-farm produced AMF inoculant, and an on-farm produced indigenous microbial inoculant on bread wheat (Triticum aestivum L.) AMF colonization, biomass accumulation, nutrient uptake and recovery, and grain yield and protein in a containerized greenhouse experiment and two years of field trials conducted in Maine, USA. The inoculants were compared with respective controls (sterilized inoculants) and the levels of N, P and K were equalized across treatments. Both AMF inoculants enhanced AMF colonization in a greenhouse potting mix containing unsterilized field soil, but only the on-farm produced AMF increased aboveground biomass and phosphorus (P) uptake and recovery. No differences were observed among inoculants and their relative controls in the field. However, the indigenous microbial inoculant (IMO+) increased wheat aboveground biomass, nutrient uptake, nutrient recovery and grain yield when compared with the mycorrhizal inoculants, but no increases were observed when contrasted against its control (IMO − ). Wheat growth enhancements from IMO were likely due to nutrient supply from the compost-based material in which it was produced. Results demonstrate that a mycorrhizal inoculant produced on-farm can increase wheat AMF colonization, aboveground biomass, and P uptake and recovery in a containerized setting. Otherwise differences between inoculants and their relative controls were limited, perhaps due to competition from the native soil microbial community, thus inoculation of field plots cannot be recommended for wheat.