title: Root foraging elicits niche complementarity-dependent yield advantage in the ancient 'three sisters' (maize/bean/squash) polyculture.
abstract: OBJECTIVE
  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 component monocultures on a land-equivalent basis. This study shows that below-ground niche complementarity may contribute to this yield advantage.
  
  
  METHODS
  Monocultures and polycultures of maize, bean and squash were grown in two seasons in field plots differing in nitrogen (N) and phosphorus (P) availability. Root growth patterns of individual crops and entire polycultures were determined using a modified DNA-based technique to discriminate roots of different species.
  
  
  RESULTS
  The maize/bean/squash and maize/bean polycultures had greater yield and biomass production on a land-equivalent basis than the monocultures. Increased biomass production was largely caused by a complementarity effect rather than a selection effect. The differences in root crown architecture and vertical root distribution among the components of the 'three sisters' suggest that these species have different, possibly complementary, nutrient foraging strategies. Maize foraged relatively shallower, common bean explored the vertical soil profile more equally, while the root placement of squash depended on P availability. The density of lateral root branching was significantly greater for all species in the polycultures than in the monocultures.
  
  
  CONCLUSIONS
  It is concluded that species differences in root foraging strategies increase total soil exploration, with consequent positive effects on the growth and yield of these ancient polycultures.
authors.affiliation: Department of Plant Nutrition, China Agricultural University, Beijing 100193, PR China Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Chaochun
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA IBG2, Forschungszentrum Juelich, D-52425 Juelich, Germany.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Postma
authors.affiliation: Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA Graduate Program in Ecology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Larry M
authors.initials: LM
authors.lastname: York
authors.affiliation: Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA JPL4@psu.edu.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Lynch
mesh_terms: D000383:Agriculture / Q000379:methods*; D018533:Biomass; D018556:Crops, Agricultural / Q000254:growth & development; D028464:Cucurbita / Q000254:growth & development*; D017753:Ecosystem; D007887:Fabaceae / Q000254:growth & development*; D009584:Nitrogen / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism; D018517:Plant Roots / Q000033:anatomy & histology / Q000502:physiology*; D018520:Plant Shoots / Q000254:growth & development; D019655:Quantitative Trait, Heritable; D003313:Zea mays / Q000254:growth & development*
chemical_list: D010758:Phosphorus; D009584:Nitrogen
keywords: Cucurbita; Phaseolus vulgaris; Zea mays; bean; intercropping; maize; niche complementarity; nitrogen; phosphorus; plant nutrition; polyculture; root architecture; root foraging; squash; ‘Three sisters’