Arbuscular mycorrhizal fungi (AMF) enhance plant phosphorus uptake, increase soil water holding abilities, reduce soil erosion and can protect their hosts from soil-borne pathogens. Hence, AMF play an important part in improving sustainable agricultural practices, and information about the effects of different preceding crop species on the following crop's AMF well-being is crucial for designing crop rotations.

We studied onion root and soil microbial diversity and onion root AMF colonization rates after being preceded by three AMF hosting and one non-hosting green manure crop species in a boreal climate organic field.

One-season cultivation of different preceding green manure crops did not have a strong effect on AMF colonization or microbial diversity in onion roots nor in the surrounding soil. Onions had high AMF colonization and microbial diversity after all four preceding crops. The overall fungal and bacterial populations of the soil reacted more strongly to seasonal variations than preceding crops.

The study suggests that one season is a too short time to influence the AMF community in boreal climate organic fields with conventional tillage. Thus, non-host preceding crops can also be used in rotations, especially together with AMF host crops.

丛枝菌根真菌 (AMF) 可增强植物对磷的吸收，增加土壤持水能力，减少土壤侵蚀，并可以保护宿主免受土传病原体的侵害。因此，AMF 在改进可持续农业实践方面发挥着重要作用，有关不同前作作物品种对后作作物 AMF 福祉影响的信息对于设计轮作至关重要。

在北方气候有机田中，我们研究了洋葱根和土壤微生物多样性以及洋葱根 AMF 定植率，然后研究了三种 AMF 寄主和一种非寄主绿肥作物物种。

不同先前绿肥作物的一季栽培对洋葱根部和周围土壤中的 AMF 定植或微生物多样性没有强烈影响。在所有四种前作作物之后，洋葱具有高 AMF 定植和微生物多样性。与之前的作物相比，土壤的整体真菌和细菌种群对季节性变化的反应更强烈。

该研究表明，一个季节的时间太短，无法影响采用常规耕作方式的北方气候有机田中的 AMF 群落。因此，非寄主前作作物也可用于轮作，特别是与 AMF 寄主作物一起使用。