ObjectivesRoot morphological and physiological plasticity is critical for plant nutrient acquisition from soil. The nutrient uptake ability of individual plant in mixture cropping system (intra-specific or inter-specific cropping systems) is strongly affected by neighboring plant presence. This paper focused on investigating the foraging behaviors and strategies of roots in mixture systems, understanding the underlying mechanism and suggesting major pathways and approaches of rhizosphere management for improving nutrient acquisition.

Major advancesThe complementarity of root traits of the neighboring plants could decrease root competition for nutrients. The difference in root architecture, i.e. deep-rooted plant intercropping with shallow-rooted plant, is beneficial to utilize soil nutrients in different soil layers. The root-placement pattern of neighboring plants driven by root plasticity improves nutrient use efficiency in different soil zones in the same soil layer. Root morphological plasticity may also exhibit a complementary effect with neighboring root physiological traits, resulting in the utilization of different fraction of nutrients in soil. Niche differentiation has been considered an important mechanism for species coexistence, including spatial niche differentiation in vertical and horizontal root distribution, and the biochemistry niche differentiation. Applying or controlling fertilizer nutrient supply at a proper level in root zone could enhance root ability for excavating soil nutrients; matching the intercropped species through optimizing plant combinations reasonably could improve nutrient use efficiency through maximizing the biological effect of root-root interactions.

Suggestions and expectationsAs for intensive farming systems, optimizing the combinations of intercropped species and the root-zone nutrient management will strengthen nutrient signaling-based rhizosphere processes and manipulation, and regulate root morphological and physiological traits, which will affect the root foraging behaviors reduce root competition and enhance root facilitation between plants and their neighbors. These strategies of root/rhizosphere interactions are critical to develop the approaches of improving nutrient use efficiency and productivity through maximizing root/rhizosphere efficiency in intensive cropping systems, and achieving " saving fertilizer and enhancing efficiency” sustainable intensification of grain production with less input and producing more.