Multispecies crop mixtures increase insect biodiversity in an intercropping experiment.
Recent biodiversity declines require action across sectors such as agriculture. The situation is particularly acute for arthropods, a species-rich taxon providing important ecosystem services. To counteract the negative consequences of agricultural intensification, creating a less hostile agricultural 'matrix' through growing crop mixtures can reduce harm for arthropods without yield losses. While grassland biodiversity experiments showed positive plant biodiversity effects on arthropods, experiments manipulating crop diversity and agrochemical input used to study arthropods are lacking. Here, we experimentally manipulated crop diversity (1-3 species, fallows), crop species (wheat, faba bean, linseed and oilseed rape) and agrochemical input (high vs. low) and studied responses of arthropod biodiversity. We tested whether arthropod responses were affected by crop diversity, mixtures and management. Additionally, we measured crop biomass. Crop biomass increased with crop diversity under high-input management, while under low management intensity, biomass was highest in two-species mixtures. Increasing crop diversity positively affected arthropod abundance and diversity, under both low- and high-input management. Crop mixtures containing faba bean, linseed or oilseed rape had particularly high arthropod diversity. Mass-flowering crops attracted more arthropods than legumes or cereals. Integrating intercropping into agricultural systems could increase flower visits by insects up to 1.5 million per hectare, thus likely also supporting pollination and pest-control ecosystem services. Flower visitor network complexity increased in mixtures containing linseed and faba bean and under low-input management. Intercropping can counteract insect declines in farmland by creating beneficial matrix habitat without compromising crop yield.