Niche Complementarity and Facilitation Determine the Performance of Plant Associations for Abiotic Resource Acquisition

In conventional agro-ecosystems, single-species stands compete intensely for the same resources, necessitating high fertilizer and water inputs. This paper reviews two processes—niche complementarity and facilitation—that underlie improved performance in multi-species associations. Complementarity arises when species differ in root depth, growth timing, or canopy structure, and when legumes fix atmospheric nitrogen in low-input systems. Facilitation occurs when one species’ rhizosphere activity mobilizes soil phosphorus otherwise unavailable. Evidence from cereal-legume intercrops shows enhanced biomass production, grain yield, nitrogen status, and protein concentration under limited inputs, highlighting the agronomic and environmental benefits of intercropping.