Subsidy type and quality determine direction and strength of trophic cascades in arthropod food web in agro‐ecosystems

1. The subsidy hypothesis states that communities receiving nutrient subsidies will demonstrate top-down trophic cascades where predators indirectly increase plant biomass. This has been both confirmed and refuted, which might depend on whether the subsidy has mainly targeted the plant or the detrital food-web compartment, and on the subsidy quality. This is particularly poorly understood for terrestrial communities such as heavily subsidized agroecosystems. 2. Using cages covering 4 m2 of ground in a long-term agricultural fertilisation experiment, we tested whether subsidies targeting the detrital soil meso-fauna compartment with organic fertilisers, or the plants with mineral fertiliser, impacted the direction and strength of trophic cascades in an arthropod-plant food-web. We expected top-down controls of generalist arthropod predators (spiders, ground and rove beetles) on aphid densities to be stronger in organically fertilised plots due to enhanced alternative prey availability in...