Designing intercrops for high yield, yield stability and efficient use of resources: are there principles?

Intercropping is the simultaneous cultivation of plant species in the same field for a considerable proportion of their growing periods. Interest in intercropping for sustainable agriculture is on the rise and the number of scientific studies on intercropping is strongly increasing. Here we assess the current status of knowledge on factors that determine yield, yield stability and resource use efficiency of intercropping as compared to sole cropping. Distinguishing resource use into acquisition and conversion shows that intercrops are mainly improving acquisition rather than conversion efficiency. We also make an attempt to quantify the importance of reduced biotic stresses through pests, diseases, and weeds. We particularly focus on blank spots in the knowledge and possible bias in existing literature and ask which research approaches are needed to advance the field and pave the way for a wider usage of intercropping in modern sustainable agriculture.