Gene-Edited Bacteria Increases Nitrogen Fixation in Corn

If corn ever felt envious of soybeans’ relationship with nitrogen-fixing bacteria, advancements in gene editing might one day level the playing field. Researchers at the University of Illinois Urbana-Champaign have demonstrated that gene-edited bacteria could provide corn with up to 35 pounds of nitrogen from the air during early growth stages, potentially reducing the crop's reliance on synthetic nitrogen fertilizers.

“To replace all synthetic nitrogen would certainly be a significant achievement. Maybe 100 years from now, we’ll have developed the microbes and genetic tweaks to come close to that goal, but these microbes aren’t there yet. Still, we have to start somewhere, and this work shows that nitrogen fixation for corn has potential,” 

Connor Sible, study co-author and research assistant professor at the University of Illinois Urbana-Champaign.

The study focused on products from Pivot Bio—specifically PROVEN and PROVEN® 40—which contain one or two species of soil bacteria capable of converting atmospheric nitrogen into plant-usable forms. The modified bacteria increase nitrogen availability by enhancing the activity of a key gene involved in nitrogen fixation. When applied during planting, the bacteria colonize plant roots and deliver nutrients directly to where they are needed most.

According to Pivot Bio, these products can replace up to 40 pounds of synthetic nitrogen fertilizer per acre with biologically fixed nitrogen. However, Logan Woodward, who conducted the study as a doctoral student at Illinois, noted, “There is a lack of peer-reviewed data to support this claim. Additionally, there’s limited research on the timing and magnitude of nitrogen replacement during the growth cycle. Our objective was to address these knowledge gaps.”

Over three field seasons, researchers employed standard agronomic practices for corn, applying nitrogen fertilizer at rates of 0, 40, 80, 120, or 200 pounds per acre at planting. At the end of each season, they measured grain yield and nitrogen content in plant tissues during the V8 stage (eight fully-collared leaves) and R1 stage (silk emergence).

The results showed that the inoculated plots enhanced nitrogen uptake from the atmosphere, complementing soil and fertilizer sources. This was evidenced by the dilution of isotopic nitrogen in plant and soil samples. Across all fertilizer rates, the inoculant increased corn vegetative growth, nitrogen accumulation, kernel number, and yield by an average of 2 bushels per acre. At moderate nitrogen rates, yields increased by 4 bushels per acre, corresponding to 10-35 pounds of nitrogen per acre of fertilizer equivalence.

However, the overall yield gains were modest. While the inoculant delivered 35 pounds of nitrogen during early growth, this benefit diminished to about 10 pounds by the end of the season. “There’s still a need for fertilizer,” said Fred Below, senior study author and professor at the University of Illinois Urbana-Champaign. “You need sufficient nitrogen to support a healthy plant, which in turn produces the root sugars needed to feed the microbes. Without enough nitrogen, the plant can’t sustain itself or the inoculated bacteria, so the efficacy of these microbes is greatly reduced in the absence of fertilizer nitrogen.”

Despite these limitations, the researchers believe the technology holds promise. While current products cannot fully replace synthetic fertilizers, they could still serve useful purposes in modern agriculture.

“Every farm has areas where the soil doesn’t provide enough nitrogen, or where fertilizer has been lost or is unavailable. A microbial inoculant providing an additional nitrogen source could help fill these gaps,” Sible explained. “In some cases, cornfields receive ‘insurance nitrogen’—an extra 20 pounds applied as a precaution against potential nitrogen loss. A nitrogen-fixing inoculant could reduce the need for those extra pounds, which would add up to a significant impact across all Corn Belt acres.”