Well, photosynthesis is not quite as simple as that. If it were, we wouldn’t need soil, water, fertilizers, or beneficial microbes. But plants need a balanced growing environment. They can’t move, so whatever conditions they germinate into, they must cope with. It’s up to you the farmer to provide that balance. Often it starts with observing.

Microbes depend on soil with organic matter and carbon that plants create as sugars and elemental carbons for food. In exchange, microbes give the plant a plethora of nutrients and water. The fertilizer, if synthetic, comes from oil reserves deep in the ground that were once plants. Natural fertilizers, such as manure, come from animals that eat plants. All life on earth revolves around the ability of a few organisms to create energy from sunlight through photosynthesis.

Photosynthesis and Plant Growth

Photosynthesis is an amazing process. Plants, algae, and cyanobacteria are the only organisms on Earth that can combine sunlight and carbon dioxide from the atmosphere to create growth. When plants photosynthesize, they create sugar molecules from carbon molecules and sunlight for internal use and to expel the oxygen we breathe. We need plants more than they need us.

Sugar molecules are the basis for other more complex molecules such as glucose, an energy source and a building block for plant processes. Plant growth, defense, and exchanges with other organisms are all dependent on photosynthesis to create those more complex molecules.

How Does Photosynthesis Pertain to Crop Growth on Your Farm?

There’s a lot of carbon dioxide (CO₂) in the air. The high quantity is a by-product of the industrial revolution. But that doesn’t necessarily mean it’s good for your crops.

There’s a myth going around that an increase in carbon dioxide increases plant growth. Wouldn’t that be super for your fields? But this is not the case.

If all growing factors are optimized—the right amount of water, great soil, perfect temperature, and optimum sunlight—plants may grow faster and larger with increased CO₂. This has been accomplished in greenhouses where all the factors could be controlled. But out on a farm field? In the open? With extremes of weather throughout the season? When you have a good year aren’t the majority of these factors optimized? You need the right amount of CO₂ but extra? Probably not.

Crops have many limiting factors to optimum growth. Carbon dioxide is not the only, or even the most important, in some situations. Drought is a persistent limiting situation in much of the United States. When temperatures are high and water low, plants choose survival and tend to increase underground growth while aboveground biomass wilts or curls. During drought, all plant processes, including photosynthesis, slow down. Plants store precious carbon instead of cycling it through the soil food web.

In drought years, for example, CO₂ from the air will be limited because the stomata (openings on the bottoms of leaves) that allow CO₂ into the plant remain open for shorter time periods to retain precious moisture. When plants choose survival, growth is stunted, fruit or seed set is less, and insects and disease have more opportunities.

Soil Organic Carbon for Optimum Plant Growth

Assuming carbon is the limiting factor and not drought or other nutrients such as nitrogen or phosphorus, other sources of carbon for plants include soil organic carbon from decaying soil organisms, crop residue, compost, cover crops, and manure. Soil organic carbon (SOC) is part of soil organic matter (SOM). Most conventional farmland today has SOM of around 1 percent,  and plants need higher amounts of SOM with SOC for optimal growth.

If you’re a conventional farmer, you till in crop residue to add carbon to the soil. This is a short-term fix that each year leaves a bit less carbon in the soil. SOC is necessary for optimum plant growth as well as food for beneficial soil microbial populations. Those microbes supply nutrients to your crops for more resilience. When you follow the trail back from manure to livestock to plant, you find that the process of photosynthesis is the basis for all SOC. If you’re using synthetic fertilizer, you’re using oil derived from the combination of sunlight, CO₂, and the process of photosynthesis of plants that lived millions of years ago.

There isn’t a one-size-fits-all for the amount of SOC needed for optimum crop performance. But most experts agree that the amount of SOM should be between 3 percent and 6 percent and SOC between 2 percent and 3 percent for optimum growth of most crops. Incorporating regenerative ag practices into your operation can bring up your SOM and SOC. What happens when you have higher SOC in your fields?

Your crops are more resilient during extreme weather events. When they have an optimum amount of carbon available, your crops can attain optimum yield, maintain their defense mechanisms against pests and disease, and have high nutritional profiles, all aspects of your operation that lead to a profitable year.

To learn more about carbon, photosynthesis, beneficial microbes, and their relationship to plants and the impact on your crop, read this blog. We’re here to help you succeed. When soil speaks, we listen.