[en] Global climate change is likely to exacerbate plant abiotic stress in the coming decades by increasing water stress and by accelerating soil fertility degradation. To respond to this set of challenges, there is a need to develop agricultural systems with significantly greater productivity and resilience that at the same time use limited natural resources more efficiently. Low phosphorus (N) and nitrogen (P) availabilities are primary limitations to productivity in low input agriculture, and fertilizers are primary resource inputs in intensive agriculture. A critical feature of future agricultural systems will be new crop varieties with improved conversion of soil resources to yields. These new cultivars would have improved productivity in low input systems and decreased input requirements in high input systems. Many scientists are currently turning their attention to roots, the hidden half of the plant, as central to their efforts to produce crops with better yields without causing environmental damage. Several root traits are known to be associated with P and N acquisition efficiency in low N and P soils. These root traits include root hairs, root length, root branching and root density. The identification of root traits for enhanced P and N acquisition is enabling crop breeders to develop new genotypes with better yields in low fertility soils of Africa, Asia and Latin America. However, in order to use a trait as a selection criterion for crop improvement, either direct phenotypic selection or through marker assisted selection, it is necessary to develop protocols to measure accurately the root traits that enhance N and P acquisition in the glasshouse and in the field, which can provide robust and rapid evaluation of many root systems' architectural traits in targeted production environments using different crops. The objective of the Coordinated Research Project on Optimizing Productivity of Food Crop Genotypes in Low Nutrient Soils was to develop integrated crop, soil and nutrient management practices that help increase crop production in marginal lands by identifying and promoting the development of food crop genotypes (cereals and legumes) with enhanced N and P usage efficiency. This CRP was implemented following the recommendations of a consultants meeting of international experts. The research network included ten contract holders from Brazil, Burkina Faso, Cameroon, China, Cuba, Ghana, Malaysia, Mexico, Mozambique and the United States of America and six agreement holders from Australia, Benin, France, Germany, Kenya and Nigeria. The CRP was conducted in collaboration with national agricultural research systems in Africa, Asia and Latin America, and with three centres of the Consultative Groups on International Agricultural Research (CGIAR): The Africa Rice Center (WARDA), the International Institute of Tropical Agriculture (IITA) and International Center for Tropical Agriculture (CIAT). The CRP was supported by in-house research and the provision of ¹⁵N/ ¹⁴N isotope ratio analysis of ¹⁵N enriched plant samples at the FAO/IAEA Agriculture and Biotechnology Laboratories, Seibersdorf, Austria. Upstream research on ¹⁵N and ³²P methodologies, protocols for evaluation of plant root traits that enhance N and P acquisition and utilization efficiencies were carried out at the IAEA prior to the commencement of the CRP and through an individual research contract