Arbuscular mycorrhizal fungi (AMF) are important in plant nutrient uptake, but their function is prone to environmental constraints including soil factors that may suppress AMF transfer of phosphorus (P) from the soil to the plant. The objective of this study was to disentangle the biotic and abiotic components of AMF-suppressive soils. Suppression was measured in terms of AMF-mediated plant uptake of ³³P mixed into a patch of soil and treatments included soil sterilization, soil mixing, pH manipulation and inoculation with isolated soil fungi. The degree of suppression was compared to volatile organic compound (VOC) production by isolated fungi and to multi-element analysis of soils. For a selected suppressive soil, sterilization and soil mixing experiments confirmed a biotic component of suppression. A Fusarium isolate from that soil suppressed the AMF activity and produced greater amounts than other fungal isolates of the antimicrobial VOC trichodiene (a trichothecene toxin precursor), beta-chamigrene, alpha-cuprenene and p-xylene. These metabolites deserve further attention when unravelling the chemical background behind the suppression of AMF activity by soil microorganisms. For the abiotic component of suppression, soil liming and acidification experiments confirmed that suppression was strongest at low pH. The pH effect might be associated with changed availability of specific suppressive elements. Indeed ³³P uptake from the soil patches correlated negatively to Al levels and Al toxicity seems to play a major role in the AMF suppressiveness at pH below 5.0–5.2. However, the documentation of a biotic component of suppression for both low and high pH soils leads to the conclusion that biotic and abiotic components of suppression may act in parallel in some soils. The current insight into the components of soil suppressiveness of the AMF activity aids to develop management practices that allow for optimization of AMF functionality.

丛枝菌根真菌（AMF）在植物养分吸收中很重要，但是其功能容易受到环境的限制，包括可能会抑制AMF将磷（P）从土壤转移到植物的土壤因素。这项研究的目的是解开抑制AMF的土壤中生物和非生物成分。抑制作用是通过AMF介导的植物对³³ P吸收到土壤中的摄取进行测量的，处理方法包括土壤灭菌，土壤混合，pH值处理以及接种分离的土壤真菌。将抑制程度与通过分离真菌产生的挥发性有机化合物（VOC）以及土壤的多元素分析进行​​了比较。对于选定的抑制性土壤，灭菌和土壤混合实验证实了抑制的生物成分。一种从该土壤中分离得到的镰刀菌抑制了AMF活性，并产生了比其他VOC抗菌剂三氯二烯（三氯噻吩毒素前体），β-香豆烯，α-铜烯和对二甲苯等真菌分离物更大的数量。当阐明土壤微生物抑制AMF活性背后的化学背景时，这些代谢物值得进一步关注。对于抑制作用的非生物成分，土壤石灰和酸化实验证实，在低pH下抑制作用最强。pH值的影响可能与特定抑制性元素的可利用性改变有关。确实是³³从土壤斑块中吸收的磷与铝水平呈负相关，铝的毒性似乎在pH值低于5.0-5.2时对AMF的抑制作用中起主要作用。但是，有关抑制低pH和高pH值土壤的生物成分的文献得出的结论是，抑制的生物成分和非生物成分在某些土壤中可能同时发挥作用。当前对AMF活性的土壤抑制成分的了解有助于开发允许优化AMF功能的管理实践。