Researchers at Aarhus University are uncovering how wheat plants may help improve nitrogen efficiency through naturally produced root compounds, a discovery that could support more sustainable grain production and reduce fertilizer losses across the supply chain.
In greenhouse trials at AU Flakkebjerg in Denmark, scientists are studying biological nitrification inhibition, or BNI, a natural process in which plant roots release compounds that suppress nitrifying microbes in the soil. These microbes convert ammonium into nitrate, a form of nitrogen that is more prone to leaching and gaseous loss.
Nitrogen remains essential to modern crop production, but less than half of the fertilizer applied to fields is typically used by plants. The remainder is lost through runoff, leaching or emissions such as nitrous oxide, a potent greenhouse gas.
For years, efforts to improve nitrogen efficiency have focused on fertilizer regulations and synthetic nitrification inhibitors. While those inhibitors can reduce nitrogen loss, they add cost, often require multiple applications and may affect non-target soil organisms.
The new research examines whether wheat can provide a biological alternative.
At the center of the work are benzoxazinoids, naturally occurring compounds found in cereals such as wheat, corn and rye. These compounds have traditionally been associated with plant defense, helping protect against insects, weeds and nematodes.
Researchers have now identified an additional function. In a recent study, 18 benzoxazinoids were tested using a bioluminescence assay with Nitrosomonas europaea, a model nitrifying bacterium. Seven of those compounds, including BOA, MBOA, DIBOA and DIMBOA, showed strong nitrification-inhibiting properties at relatively low concentrations.
Because the compounds are naturally produced by the plant and released through the roots, researchers believe they may offer a more targeted and continuous approach to nitrogen management than synthetic products.
The study compared three wheat lines, including a conventional parent line and two BNI wheat lines carrying a chromosome segment from the wild grass Leymus racemosus, which is known to strengthen BNI traits.
In hydroponic trials, the BNI wheat lines released significantly greater amounts of active benzoxazinoids than the parent line. Their root exudates also suppressed nitrification at up to twice the rate of the conventional line.
Researchers said the findings could have practical implications for wheat breeding and long-term nitrogen management strategies.
Modeling suggests BNI-enabled crops could reduce nitrogen losses by 20% to 30%, while early field trials have shown no reduction in grain yield. That combination could allow producers to lower fertilizer use without sacrificing output.
For flour millers and wheat processors, improvements in nitrogen-use efficiency at the farm level could strengthen sustainability metrics and potentially support more stable production costs in wheat supply chains.
Scientists also note that plant-based nitrification inhibition may carry fewer unintended consequences for soil biology because the compounds are released gradually in the root zone rather than applied broadly.
Ongoing work through the CropSustain project is examining how these BNI traits affect broader soil microbial communities and non-target organisms over time.
Researchers say the next step will be identifying the biosynthetic pathways behind the most effective compounds, giving breeders the ability to select wheat varieties with stronger BNI traits.
If successful, the approach could provide wheat growers with a built-in biological tool for improving nitrogen efficiency while reducing environmental losses, offering benefits across grain production and processing.
Source: Aarhus University, "When wheat learns to protect the nitrogen"