Paper Reviewed
Li, X., Ulfat, A., Shokat, S., Liu, S., Zhu, X. and Liu, F. 2019. Responses of carbohydrate metabolism enzymes in leaf and spike to CO2 elevation and nitrogen fertilization and their relations to grain yield in wheat. Environmental and Experimental Botany 164: 149-156.

Wheat is one of the most studied agricultural crops in CO2 enrichment studies. The latest research team to investigate its response to future predicted levels of atmospheric CO2 comes from Li et al. (2019).

Writing in the journal Environmental and Experimental Botany, the six researchers investigated the interactive effect of CO2 and nitrogen fertilization on the cultivar Lianmai6. The wheat plants were grown in a climate-controlled greenhouse to maturity at the University of Copenhagen, Tåstrup, Denmark from December 2016 to April 2017. In the full-factorial experiment, nitrogen fertilization was applied as normal (N1 treatment; 1 g N applied as NH4NO3) or twice-normal (N2 treatment; 2 g N applied as NH4NO3) and atmospheric CO2 concentrations were maintained at ambient (400 ppm) or twice-ambient (800 ppm). The results are presented in the figure below.

As seen in Figure 1, elevated CO2 stimulated both net photosynthesis (An) and grain yield. In the N1 treatment these two parameters increased by 12.3% and 10.0%, respectively, whereas in the N2 treatment they rose by 21.4% and 11.4%, also respectively. And whereas elevated CO2 had a significant, positive effect on photosynthesis and growth, no significant impact was noted for nitrogen supply treatment, nor was there any significant interaction between CO2 level and nitrogen supply.

Thus, we have yet another example demonstrating that rising levels of atmospheric CO2 will benefit crop grain yields. And that is great news for the future food security of the planet.

Figure 1. Net photosynthesis (An, Panel A) and grain yield (Panel B) of wheat growing under ambient (400 ppm) or elevated (800 ppm) atmospheric CO2 at two different nitrogen fertilizer rates (N1 and N2 for normal and twice-normal application rates, respectively). Mean values ± SE are shown. The red text indicates the percent enhancement in net photosynthesis and grain yield due to elevated CO2 at a given nitrogen treatment level. ** = significance at P < 0.05, ns = not significant (Tukey's test). Source: Li et al. (2019).