title: Crop acquisition of phosphorus, iron and zinc from soil in cereal/legume intercropping systems: a critical review.
abstract: BACKGROUND
  Phosphorus (P), iron (Fe) and zinc (Zn) are essential elements for plant growth and development, but their availability in soil is often limited. Intercropping contributes to increased P, Fe and Zn uptake and thereby increases yield and improves grain nutritional quality and ultimately human health. A better understanding of how intercropping leads to increased plant P, Fe and Zn availability will help to improve P-fertilizer-use efficiency and agronomic Fe and Zn biofortification.
  
  
  METHODS
  This review synthesizes the literature on how intercropping of legumes with cereals increases acquisition of P, Fe and Zn from soil and recapitulates what is known about root-to-shoot nutrient translocation, plant-internal nutrient remobilization and allocation to grains.
  
  
  CONCLUSIONS
  Direct interspecific facilitation in intercropping involves below-ground processes in which cereals increase Fe and Zn bioavailability while companion legumes benefit. This has been demonstrated and verified using isotopic nutrient tracing and molecular analysis. The same methodological approaches and field studies should be used to explore direct interspecific P facilitation. Both niche complementarity and interspecific facilitation contribute to increased P acquisition in intercropping. Niche complementarity may also contribute to increased Fe and Zn acquisition, an aspect poorly understood. Interspecific mobilization and uptake facilitation of sparingly soluble P, Fe and Zn from soil, however, are not the only determinants of the concentrations of P, Fe and Zn in grains. Grain yield and nutrient translocation from roots to shoots further influence the concentrations of these nutrients in grains.
authors.affiliation: National Engineering Laboratory for Wheat and Maize, Maize Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China.
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Xue
authors.affiliation: National Engineering Laboratory for Wheat and Maize, Maize Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China, Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Crop Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China, drhaiyongxia@gmail.com C.Tang@latrobe.edu.au.
authors.forename: Haiyong
authors.initials: H
authors.lastname: Xia
authors.affiliation: Ministry of Education Key Laboratory of Plant and Soil Interactions, Center for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China and.
authors.forename: Peter
authors.initials: P
authors.lastname: Christie
authors.affiliation: Shandong Provincial Key Laboratory of Crop Genetic Improvement, Ecology and Physiology, Crop Research Institute, Shandong Academy of Agricultural Sciences, Jinan 250100, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Ministry of Education Key Laboratory of Plant and Soil Interactions, Center for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China and.
authors.forename: Long
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Animal, Plant and Soil Sciences, Centre for AgriBiosciences, La Trobe University, Melbourne Campus, Bundoora Vic 3086, Australia drhaiyongxia@gmail.com C.Tang@latrobe.edu.au.
authors.forename: Caixian
authors.initials: C
authors.lastname: Tang
mesh_terms: D000383:Agriculture / Q000379:methods*; D018556:Crops, Agricultural / Q000378:metabolism*; D007887:Fabaceae / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D015032:Zinc / Q000378:metabolism*
chemical_list: D012987:Soil; D010758:Phosphorus; D007501:Iron; D015032:Zinc
keywords: Biofortification; cereals; intercropping; interspecific facilitation; legumes; micronutrients; niche complementarity; phosphorus; rhizosphere; root architecture; root exudates; soil microbes.