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

Abstract

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.

Mutual plant-fungi symbiosis compromised by fungicide use

“…Agricultural productivity is an increasingly important topic as the global population increases, and the security of food supplies becomes more precarious. However, soil health is negatively impacted both by intensive farming and by climate change, in part due to altered microbial and fungal biodiversity 1 . Arbuscular mycorrhizal fungi (AMF) are found in the soils of most terrestrial ecosystems, where they facilitate nutrient uptake by (and exchange between) plants.…”

“…Plants provide AMF in the soil with sugars and lipids, and receive nutrients such as nitrogen and phosphorus from AMF in return. In nutrient-poor soils, AMF may provide the majority of the nutritional requirements of host plants 1 .…”

“…A recent study led by Marcel G. A. van der Heijden at Agroscope and the University of Zürich (Edlinger et al 1 ) found that AMF diversity was lower in cereal-producing farmland soils than in grassland soils, because AMF are negatively impacted by agricultural practices such as plowing or the use of fungicides and inorganic fertilizers 1 . Other studies observed similar reductions in microbial and fungal diversity in the soils of other agricultural systems, such as vineyards 2 , 3 , orchards 3 , and arable crops 4 .…”

“…Other studies observed similar reductions in microbial and fungal diversity in the soils of other agricultural systems, such as vineyards 2 , 3 , orchards 3 , and arable crops 4 . Most modern crop plants have not been bred with this symbiotic relationship with AMF in mind, and thus are only inefficiently colonized by AMF 1 .…”

“…The study by Edlinger et al . 1 examined the growth of plants in grassland, cultivated (arable farmland), and sterile control soil, using Plantago lanceolata L. (Plantaginaceae) as a model species. A genomic analysis was used to characterize the microbial diversity present in the soil, and nutrient (phosphorous) transfers were analyzed in a compartment system using the radio-isotope, 33 P. The authors found considerable differences between the farmland and grassland soils, with lower hyphal 33 P transfer in the farmland soil.…”