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Abstract

Arbuscular mycorrhizal fungi (AMF) are important root symbionts that provide increased access to soil nutrients such as phosphates and nitrates, and in turn utilize plant-derived carbon, leading to improved plant growth. This has led to their increased use in agriculture as biofertilizers. Their efficacy as biofertilizers is dependent on their ability to establish in a plant root and in the soil environment. However, problems with their successful application and effective practices continue to arise. These inoculants can also present ecological threats through risk of invasion by outcompeting resident AMF communities in soil and can therefore change soil and plant community dynamics. This study aimed to examine different factors affecting AMF establishment in agricultural soils and their impacts on resident AMF communities in the soil and plant host performance, specifically (a) inoculation timing, (b) inoculant identity, and (c) fertilization and tillage, using manipulative greenhouse experiments. In the first experiment, fertilization, tillage, and AMF identity, affected AMF establishment and resident AMF community composition in the soil. High fertilization and tillage reduced inoculant establishment, while context-dependent differences in their establishment success among AMF inoculants were observed. Resident AMF communities and plant host responses were strongly influenced by the interaction between inoculant identity and fertilization and tillage. In the second experiment, inoculation timing and AMF identity were found to influence AMF establishment but did not translate into either measurable shift in resident AMF community structure or enhanced plant responses. Overall, these findings emphasize that AMF inoculation outcomes depend on both AMF inoculant traits and soil management context. Effective application of AMF-based biofertilizers requires matching inoculant selection with site-specific nutrient and disturbance regimes and soil conditions. Field validation and functional analyses are necessary to fully assess AMF performance and long-term ecosystem effects. Results from this study aim to give insights into the wide-ranging effects of AMF on agroecosystems and the development of best practices on AMF biofertilizer application.