Effects of Elevated Atmospheric CO₂ Concentration on Growth, Grain Yield and Grain Macronutrient Concentrations of Wheat Under Different K Supply

ABSTRACT Background Atmospheric carbon‐dioxide concentration ([CO 2 ]) is increasing rapidly, but its interactions with potassium (K) fertiliser on wheat growth, grain yield and quality are not well understood. Aim We investigated the effects of ambient CO 2 (aCO 2 , approx. 415 ppm) and elevated CO 2 (eCO 2 , 760 ppm) on these growth parameters under optimum (2.01 mol m −3 ) and growth limiting (50 mmol m −3 ) K supply in controlled environment chambers. Results Potassium limitation decreased total biomass at anthesis and maturity by approx. 13% and grain yield by 7.4%. The decreased grain yield was linked to decreased grain number. Grain K, P and S concentrations decreased by 6.5%–20.6%, under K deficiency, whereas Ca concentration increased by 8.0% and N and Mg concentrations were unaffected. These changes were closely correlated with changes in total aboveground nutrient accumulation, which were interpreted as changes in nutrient uptake. However, nutrient harvest index (NuHI) changed little with K supply. Under e[CO 2 ], plant dry weight at anthesis, root + straw dry weight at maturity and grain yield were respectively 33.1%, 23.9% and 9.7% greater than at a[CO 2 ]. The increase in yield was linked to an increase in thousand grain weight. Grain macronutrient concentrations (except P) decreased by 6.38%–16.0% with e[CO 2 ]. Total aboveground macronutrient accumulation and NuHIs were unaffected by CO 2 supply, except for KHI, which decreased with increasing [CO 2 ]. Conclusion It is concluded that uptake of nutrients and their translocation within the plant were not inhibited by eCO 2 , and decreased grain macronutrient concentrations were attributed to nutrient dilution due to increased C fixation relative to nutrient uptake.