More beneficial insects and fewer pests in mixed crops

Researchers evaluate the benefits compared to monocultures with a meta-analysis

The global decline in biodiversity is serious. Agricultural land use is a major contributor - especially the large-scale cultivation of individual crops in monocultures. Mixed crops can counteract this: There are more beneficial arthropods, such as insects and spiders, in fields where different crops grow simultaneously than in monocultures. At the same time, fewer pests occur. Researchers at the University of Göttingen found this out with a systematic literature and statistical meta-analysis. It is particularly advantageous when cereals and legumes are combined and planted in strip or row cropping. The results have been published in the journal Agriculture, Ecosystems & Environment.

The researchers evaluated 63 published articles comparing mixed and monocultures from 18 countries. They compared species diversity, number of individuals (abundance) and density per plant of beneficial and harmful arthropods. They also looked at individual groups of beneficial arthropods: Pollinators, Decomposers, and Predators and Parasitoids that kill pests. In addition, they investigated how different combinations and spatial arrangements of crops in mixed cultures influence the occurrence of these animals.

The species diversity of beneficial arthropods is 27 percent higher in mixed crops than in monocultures. Their abundance is 36 percent higher and their density per plant 94 percent higher. Different groups of beneficial arthropods benefit differently from mixed crops: species diversity and abundance of pollinators, predators, and parasitoids are greater than in monocultures, but there is no difference for decomposers. Harmful arthropods occur less in mixed crops than in monocultures: their abundance is 38 percent lower, and their density per plant is 41 percent lower. Their species diversity does not differ between cropping systems. Simultaneous cultivation of cereals and legumes outperforms the combination of different cereals in promoting beneficial insects and reducing pests. It is also more effective when crops are grown in strips or rows rather than sown in disordered mixed cropping or staggered cropping.

According to the researchers, the results show how sustainable agricultural practices can promote biodiversity and related ecosystem services. -Our results suggest that mixed cropping is an effective way to mitigate the adverse effects of intensive agriculture on beneficial arthropods in agroecosystems,- says first author Dr. Anjaharinony Rakotomalala, now a postdoctoral researcher at the University of Marburg. -The results should encourage policymakers to provide incentives in agri-environmental programs for the conversion of monocultures to mixed crops- add Dr. Anoush Ficiciyan and Teja Tscharntke from the Department of Agroecology at the University of Göttingen.

Original publication: Anjaharinony A. N. A. Rakotomalala et al. Intercropping enhances beneficial arthropods and controls pests: A systematic review and meta-analysis. Agriculture, Ecosystems & Environment (2023). DOI: 10.1016/j.agee.2023.108617