Plant growth and water economy of Solanum tuberosum in response to doubled CO2: Interaction between potassium and phosphorus

Abstract Potassium (K) and phosphorus (P) are essential macronutrients for potato ( Solanum tuberosum L.); they play crucial roles in photoassimilate production that can also be affected by elevated atmospheric CO 2 concentration (e[CO 2 ]). However, the interactive effects of K and P nutrition under e[CO 2 ] in potato have not been investigated. A pot experiment was carried out on potato plants in 1‐L pots with five K supply rates at two P supply rates in controlled‐environment chambers with ambient CO 2 concentrations (a[CO 2 ]) and an e[CO 2 ] level of double a[CO 2 ]. There was a significant interaction between K supply and P supply, but not between CO 2 and K supply on total plant biomass, water use as well as water‐use efficiency (WUE). K supply could remarkably enhance the accumulation of plant biomass under e[CO 2 ] by promoting tuber formation. The maximum total plant biomass increased by approximately 1.3‐fold under e[CO 2 ] in this study, while the effect of CO 2 was dependent on both P and K supply. Additionally, WUE was increased by e[CO 2 ] and P and K supply. Both CO 2 enrichment and K supply increased WUE by stimulating biomass accumulation and reducing water consumption. We concluded that the CO 2 ‐fertilization effect and WUE were dependent on both P and K supply. Less biomass accumulation in response to K supply in plants with P deficiency indicates that a balanced nutrient status is crucial for crop production under e[CO 2 ].