The role of carbon dioxide on closing yield gap

Over the past few decades, a dramatic increase in crop yield has been achieved as a consequence of management practices and breeding technology, and to meet the food demand resulting from population growth. However, a stronger increase in crop grain demand is expected because of the increasing population and changing diet (Neumann et al., 2010). Therefore, understanding how much crop potential needs to excavate is crucial to the food supply.

Many researchers have studied the difference between actual yield and potential yield (called yield gap, the definition of yield gap and different yield were introduced in our another blog, see http://www.lpicea.com/what-is-the-yield-gap-how-to-calculate-the-yield-gap/) based on the statistical analyses (Johnston et al., 2011; Licker et al., 2010) and/or crop models (Václavík et al., 2013), and the solutions for closing yield gaps (Foley et al., 2011). These studies focused on closing yield gaps through management practices, such as nutrient and water management. But when the water conditions and filed managements are hardly improved, what is the next pathway for closing the yield gap? Some inspiration from natural plants may answer this question.

In the past three decades, it has been found that our Earth is greening. And scientists found this greening was mainly caused by rising CO₂ (Zhu et al., 2016). The elevated CO₂ increases photosynthesis and promote water use efficiency of plants, which means plants have higher productivity and the water stress will relieve. This effect is called CO₂ “fertilization” (Thompson et al., 2004). Crops are cultivated plants and have similar photosynthetic processes as natural plants. So do crops have higher grain yield when the CO₂ rising? The free-air carbon dioxide enrichment (FACE) field experiment might tell us something.

Recently, the research published in Global Change Biology summarized the results of FACE in the past three decades of crops (Ainsworth and Long, 2020). This research found C₃ crops would be more productive in elevated CO₂, but the positive response would be diminished by nitrogen deficiency and wet conditions (see figure 1). What’s more, this review pointed out there was a strong correlation of yield response under elevated CO₂ to potential yield. This is to say elevated CO₂ might close the difference between actual yield and potential yield, but the effect varies in different regions (Broberg et al., 2019). The obvious closing effects might be found in low yield regions, but less effective in high yield regions (Ainsworth and Long, 2020; Broberg et al., 2019).

The positive effects of elevated CO₂ on increasing yield have been observed by FACE experiments. So, It would be optimistic that the increasing CO₂ concentration in the atmosphere may become a new pathway for closing yield gaps when the water conditions and filed managements are hardly improved. Many studies have reported the roles of nutrition and water management on closing yield gap relying on crop model or statistical analyses, but these studies ignored the effects of elevated CO₂ because of the unattainable mothed in statistical analyses and the weak representation of CO₂ effects in models. So it is of great significance that developing a mechanism crop model, which well represents CO₂ effects on crop growth, for studying how to close the yield gap more efficiently.

References:

Ainsworth, E.A. and Long, S.P., 2020. 30 years of free-air carbon dioxide enrichment (FACE): What have we learned about future crop productivity and its potential for adaptation? Glob Chang Biol.

Broberg, M.C., Högy, P., Feng, Z. and Pleijel, H., 2019. Effects of Elevated CO2 on Wheat Yield: Non-Linear Response and Relation to Site Productivity. Agronomy, 9(5).

Foley, J.A. et al., 2011. Solutions for a cultivated planet. Nature, 478(7369): 337-42.

Johnston, M. et al., 2011. Closing the gap: global potential for increasing biofuel production through agricultural intensification. Environmental Research Letters, 6(3).

Licker, R. et al., 2010. Mind the gap: how do climate and agricultural management explain the ‘yield gap’ of croplands around the world? Global Ecology and Biogeography, 19(6): 769-782.

Neumann, K., Verburg, P.H., Stehfest, E. and Müller, C., 2010. The yield gap of global grain production: A spatial analysis. Agricultural Systems, 103(5): 316-326.

Thompson, S.L. et al., 2004. Quantifying the effects of CO2-fertilized vegetation on future global climate and carbon dynamics. Geophys Res Lett, 31(23).

Václavík, T., Lautenbach, S., Kuemmerle, T. and Seppelt, R., 2013. Mapping global land system archetypes. Global Environmental Change, 23(6): 1637-1647.

Zhu, Z.C. et al., 2016. Greening of the Earth and its drivers. Nature Climate Change, 6(8): 791-795.

Acknowledge:

The author thanks Han Wang’s comments for this blog, and also thanks the suggestions from Han Wang, I. Colin Prentice and Sandy P. Harrison for our ongoing project about studying yield gap.