CO2: The Greatest Fertilizer of All

Oct 11, 2018 | Global Food and You, Sustainable Agriculture |

The Dirt:

More CO2 in the atmosphere means stronger, healthier plants. Yes, it is true, carbon dioxide is the perfect fertilizer for all things green. It helps the food we grow withstand drought and increases the yield per acre. Will rising CO2 put our food at risk?

The more CO2 that is available to a plant, the more CO2 it ‘inhales!’ The more CO2 it inhales, the faster the rate of photosynthesis and the greater rate of growth. Additionally, more carbon dioxide provides plants a stronger immune system to protect against disease and drought.

CO2 helps plants increase yield.

“We realize that increases in CO2 concentrations and adaptive management can provide significant mitigation of the negative effects of climate change.” -Massachusetts Institute of Technology

Dr. Craig D. Idso, author of Climate Change: The Facts 2017 and Founder of CO2 Science has closely reviewed the COfertilization effect on agriculture. He has examined a database of over 5,500 studies that include 950 plants that demonstrate how COenrichment increases photosynthesis and yield. The COin greenhouses was amplified from 300 to 600, and in some cases to 900ppm. He found that the large-scale staple food and animal crops  (soybeans, wheat, and corn)also react well to more COin the atmosphere.

Large-scale agricultural crops respond well to CO2 enrichment. In the studies led by Craig Idso, the yield of corn increased by 27%, wheat by 37%, and soybeans by 50%.

However, it is one thing to enrich the air in a greenhouse, but how does this work with crops in practical field applications?

Dr. Rob Norton, formerly Director of the International Plant Nutrition Institute, now retired as a consultant, Norton Agronomic P/L from Australia and New Zealand, has completed several studies to understand the CO2 effect on wheat. He used FACE (Free Air Carbon Dioxide) which is the ability to determine the effect of elevated CO2 on a specific crop. For example, on the same field with the same water, sunlight and fertilizer, he had two sets of crops: one had enriched air of a higher CO2 level of 550 ppm, pumped through sprinkler-like devices every few seconds, and the other wheat crop relied just on the CO2 found in the air at the time of 385 ppm. He found that the wheat grain yield increased by 50%. His research also showed that the nutrients within a plant decreased as the yield increased. (Check out our post on how minerals get diluted as the plants grow bigger with CO2 fertilization.)

CO2 helps plants cope with drought stress.
Plants have leaf stomatal pores that allow them to “inhale” carbon dioxide and release water vapor – the process of transpiration. The more CO2 they have, the fewer pores they create, the less water vapor they release. The plants are essentially storing water and energy in their leaves. Just like humans, when plants are hydrated they grow stronger and stay healthier. This is particularly true for C4 plants such as sugarcane, sorghum, and corn.
Nature Magazine published a report by Daniel Taub, Chair of Biology at Southwestern University, which examined the Photosynthetic assimilation of CO2 to the metabolism of plants. He also completed FACE experiments and compared photosynthesis between CO2 of 385 ppm to an elevated CO2 of 475 ppm – 600 ppm. He found that in the higher CO2 environment plants required less water. This has an added benefit of less run-off which keeps the soil moist over a longer period of time.
Across a variety of FACE experiments, growth under elevated CO2 decreases stomatal conductance of water by an average of 22%…. Under elevated CO2 most plant species show higher rates of photosynthesis, increased growth, decreased water use and lowered tissue concentrations of nitrogen and protein.” (Daniel Taub, Southwestern University)

The more CO2 plants absorb, the greater the rate of photosynthesis.
Image: view from a Super Cub in the Pennsylvania countryside.

Is the Earth turning greener?
Australian scientist, Randall Donohue and a group of researchers from the Commonwealth Scientific and Industrial Organization looked at the relationship between annual rainfall, rising CO2 and the greening of the earth. Through satellite measurements between 1982 – 2010, they calculated, that yes, indeed, there was a global foliage increase of 11%.
While we are frequently inundated with the consequences of excess CO2 and its relationship to climate change— what isn’t making headlines is how increased levels of CO2 can actually grow more food!

Can research utilize CO2 to increase yield even more?

As a Dirt-to-Dinner reader, by now you know that a higher crop yield on existing land is the holy grail of farming. As the world population grows and our need for sustainability increases, using innovation and technology to get the most of our existing farmland will continue to be critical. Rice is a good start as it provides at least 20% of the energy for over 50 percent of the world population.

Paul Quick, from the International Rice Research Institute in the Philippines, is working with scientists in eight different countries from 12 universities to supercharge the photosynthesis process in rice to increase its yield by 50%. According to the IRRI, each hectare of rice (2.5 acres) in Asia produces enough food for 27 people, as 2050 approaches, that same hectare will need to feed 43 people. They are working to convert rice, which is a C3 plant, to the efficient user of CO2 and water of a C4 plant. This would produce the desired 60% increase in yield.

The Bottom Line:
While the world is worried about the negative effects of carbon dioxide on temperature, the silver lining is that increased levels of CO2 help plants grow stronger and improve yield. Growing plants and other vegetation are also carbon sinks and help remove CO2 from the atmosphere. Agriculture will not be at risk because of CO2 fertilization.