In many low input agricultural systems, phosphorus (P) is one of the most limiting mineral nutrients for plant production. Although applying P fertilizer, if available, is the most performing practice, this should be accompanied by other measures. The use of genetically enhanced plants with improved P acquisition efficiency may represent a sustainable solution to increase crop yields in these systems. This review is intended to provide a summary on adaptation mechanisms of crop plants facing P deficiency as the starting point to develop a research approach for improving P acquisition efficiency. P acquisition efficiency in this review refers to external P efficiency. The suggested research approach includes three strategies: molecular assisted plant breeding, deployment of transgenic plants and the use of agricultural practices. The natural source for improving P nutrition of plants is the existing large genetic variation for plant traits that are associated with P acquisition efficiency and will therefore be emphasized in this review.