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RESEARCH PRODUCT

Impact of land use, pesticide application and agricultural management practices on the phosphorus foraging capacity of mycorrhizal fungi in 217 european agricultural soils

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More than 80% of vascular plants form symbiotic associations with arbuscular mycorrhizal fungi (AMF). Several studies have shown the potential of AMF to provide plants with phosphorus (P) via their hyphal network. Most of these studies have been performed in the greenhouse under controlled conditions using standardized soil mixtures. However, few studies have investigated hyphal P transfer in natural soils, severely limiting our understanding of the main drivers of P transfer by AMF in real agricultural soils. As a consequence, the potential of using AMF as a tool to increase crop yield remains a mystery. Using agricultural soils from a large field observation study in Europe, we aimed at answering the following questions: 1. Is hyphal P acquisition impacted by land use and agricultural management? 2. What are the main biotic and abiotic drivers of P transfer by AMF in extensively managed grassland vs. arable soils?To approach these questions, we collected soils from 59 grassland and 158 arable sites across a 3000 km European gradient. These soils were planted with Plantago lanceolata in pots in the greenhouse. The pots contained a hyphal compartment, inaccessible for plant roots. The hyphal compartments were labelled with radioactive 33P in order to estimate the capacity of hyphae to acquire P and allocate it to the growing plants.Hyphal P transfer occurred in both land use systems. Lowest P transfer rates were found in conventionally managed arable soils while transfer rates tended to be higher in grasslands. The P that was transferred from injected P pools to plants via AMF ranged from almost 0 to up to 60 %. This high variation in hyphal P transfer was explained by soil properties and management practices. Available soil P, pH and soil bacterial richness explained much of the variation of hyphal P transfer in extensive grassland soils. In contrast, fungicide application by farmers, which correlated negatively with hyphal P transfer, was the best predictor in arable soils explaining about 50% of the variation in P transfer via AMF.In conclusion, this study demonstrates that AMF can transfer substantial amounts of P to their host plants. However, intensive agricultural management practices such as fungicide application stifle their activity in agricultural soils.