Across the history of agriculture, the soil beneath our feet has been an unexplored frontier. New discoveries are showing how plants and microbes interact in order to provide the plant with more nutrients. One area that is particularly exciting is gaining a better understanding of how plants and microbes ‘communicate’ using natural biochemistry, exchanging signals that influence both plant and microbial physiology. That’s where the SOURCE story starts. First, it’s important to understand how nitrogen fixation and phosphate solubilization work.
Free living nitrogen fixation
Nitrogen is the most important nutrient in agriculture, impacting overall plant health and yield potential. Through a process known as biological nitrogen fixation, specialized bacteria called diazotrophs “fix” atmospheric nitrogen, making it available to the plant. The most well-understood example of this type of nitrogen fixation is found in legumes, such as soybean and alfalfa, where bacteria fix nitrogen inside plant root nodules. This symbiotic relationship is critically important in agriculture and nutrient cycling, but does not exist in cereal crops like corn and wheat.
There are different diazotrophic bacteria that perform free living nitrogen fixation without the need for a host plant. Although these bacteria are less understood than their symbiotic counterparts, interest in how they work is increasing because of their potential use as a source of sustainable fertilizer to help promote plant growth.
Like nitrogen, phosphate is a critical nutrient in agriculture, helping plants reach maximal growth and yield potential. The phosphate present in the soil typically exists in an insoluble, or unavailable form, which means that the plant is unable to absorb it through the roots and benefit from the nutrient. Microbes are required to solubilize phosphate into a chemically available form that the plant can use. When plants need more phosphate they release biochemical signals into the soil to attract phosphate solubilizing microbes that help the plant take in phosphorus and other nutrients.
The making of SOURCE
Understanding the full process around microbial free living nitrogen fixation and phosphate solubilization is still a work in progress, but what we know suggests that plant signals have a role in both. Because plant biochemical signals are difficult to synthesize and are relatively unstable, they are not widely used in agriculture to support plant growth. To deal with that challenge, Sound Agriculture designed and synthesized an active ingredient that is structurally similar to a plant biochemical signal, with the idea that it could be used to stimulate phosphate solubilization and nitrogen fixation, the two most agronomically important soil biofertilizer activities.
At Sound Agriculture, our team of researchers have discovered that the active ingredient in SOURCE does in fact stimulate both of these activities in the laboratory. Increases were seen in the amount of solubilized phosphate in cultures of soil bacteria, as well as an indicator of nitrogen fixation activity, the expression of nitrogenase genes.
After three years of promising field trials, SOURCE is now commercially available to corn farmers. To date, results show that growers using SOURCE have an average 8-10 bushel per acre increase with an 85% win rate. The product will be available for use on additional crops in 2021.
What this means for sustainable agriculture
A soil’s native microbiome is an untapped resource for enhancing natural fertilizer production for plants. Sound has found a new way to influence the native microbiome to solubilize more phosphate and fix more nitrogen with the potential to dramatically reduce the reliance on chemical fertilizer while increasing the health of the soil’s native microbiome.