Since ancient times in the Americas, maize, bean and squash have been grown together in a polyculture known as the ‘three sisters’. This polyculture and its maize/bean variant have greater yield than their respective monocultures. Zhang et al. grow mono- and polycultures in field plots with different nutrient availabilities and show that one cause of this yield advantage is that the crops have different, possibly complementary, root foraging strategies. Maize forages relatively shallower, common bean explores the vertical soil profile more equally, while the root placement of squash depends on P availability. Species differences in root foraging strategies increase total soil exploration, with consequent positive effects on the yield and resilience of these ancient polycultures.
One cause of the yield advantage in the 'three sisters' polyculture is that the crops have different, possibly complementary, root foraging strategies.