Arthropod activity density and predation are supported by mixed cropping of maize with common sainfoin (Onobrychis viciifolia) and reduced tillage

Mixed cropping with legumes may mitigate negative impacts of maize, Zea mays L. (Poaceae), production on arthropods by providing additional habitat structures and food resources. Still, knowledge about effects of less common legume partner crops for mixed cropping of maize is scarce. Activity density of epigeic predatory arthropods and proxies for ecosystem functions related to biological pest control were assessed on an experimental field. Plots of mixed cropping of maize and sainfoin, Onobrychis viciifolia Scop. (Fabaceae), and respective single plant species (plot size: 6 × 5 m; n = 48) differed in combination of the seed rate of each partner crop and tillage treatment. Using the “rapid ecosystem function assessment” approach in each plot on three occasions, we tested whether the activity density of generalist arthropod predators and their associated ecosystem functions can be promoted by mixed cropping of maize with sainfoin. Our data show that, compared with tilled maize as a pure culture, mixed cropping can increase activity density of generalist arthropod predators and insect predation potential but effects were limited to strip-tilled cropping systems and partly depended on sampling date. Thus, from an ecological viewpoint, mixed cropping of sainfoin and maize in strip-till systems offers the possibility to promote predatory insects and their potential for pest regulation. However, this system is inherently more prone to weed occurrence. Competition effects between cropping partners and weeds may reduce yields and hence lead to trade-offs between enhancement of arthropods and economic viability.