Agricultural management and pesticide use reduce the functioning of beneficial plant symbionts

Phosphorus (P) acquisition is key for plant growth. Arbuscular mycorrhizal fungi (AMF) help plants acquire P from soil. Understanding which factors drive AMF-supported nutrient uptake is essential to develop more sustainable agroecosystems. Here, we collected soils from 150 cereal fields and 60 non-cropped grassland sites across a 3,000 km trans-European gradient. In a greenhouse experiment, we tested the ability of AMF in these soils to forage for the radioisotope (33)P from a hyphal compartment. AMF communities in grassland soils were much more efficient in acquiring (33)P and transferred 64% more (33)P to plants compared to AMF in cropland soils. Fungicide application best explained hyphal (33)P transfer in cropland soils. The use of fungicides and subsequent decline in AMF richness in croplands reduced (33)P uptake by 43%. Our results suggest that land-use intensity and fungicide use are major deterrents to the functioning and natural nutrient uptake capacity of AMF in agroecosystems.