Quantifying Phosphorus and Water Demand to Attain Maximum Growth of Solanum tuberosum in a CO2-Enriched Environment

Growth promotion by ambient CO 2 enrichment may be advantageous for crop growth but this may be influenced by soil nutrient availability. Therefore, we quantified potato ( Solanum tuberosum L.) growth responses to phosphorus (P) supply under ambient (a[CO 2 ]) and elevated (doubled) CO 2 concentration (e[CO 2 ]). A pot experiment was conducted in controlled-environment chambers with a[CO 2 ] and e[CO 2 ] combined with six P supply rates. We obtained response curves of biomass against P supply rates under a[CO 2 ] and e[CO 2 ] (R 2 = 0.996 and R 2 = 0.992, respectively). A strong interaction between [CO 2 ] and P was found. Overall, e[CO 2 ] enhanced maximum biomass accumulation (1.5-fold) and water-use efficiency (WUE) (1.5-fold), but not total water use. To reach these maxima, minimum P supply rate at both [CO 2 ] conditions was similar. Foliar critical P concentration (i.e., minimum [P] to reach 90% of maximum growth) was also similar at nearly 110 mg P m −2 . Doubling [CO 2 ] did not increase P and water demand of potato plants, thus enabling the promotion of maximum growth without additional P or water supply, but via a significant increase in WUE (9.6 g biomass kg −1 water transpired), presumably owing to the interaction between CO 2 and P.