Soil bacteria help wheat slash its need for fertilizer

Climate watchers and wheat growers share the same worry: fertilizer dependence is pushing production costs up while adding more heat-trapping gases to the sky. Scientists are hunting for ways to keep harvests healthy without pouring on synthetic nitrogen.

The latest research points to an unexpected ally, the soil microbes that cling to wheat roots and help the plant manage its own nitrogen use.

Wolfram Weckwerth of the University of Vienna and his global team see this partnership as the key to hardier crops and cleaner fields.

Fertilizer adds heat and expense

Farmers apply ever more nitrogen in a bid to keep yields steady, yet 40 to 68 percent of that fertilizer vanishes into air and water. Those losses raise costs and send reactive nitrogen downstream.

In 2022, the global appetite for nitrogen fertilizer hit about 190 million tons, according to the Food and Agriculture Organization. The figure is projected to climb as diets shift toward grain fed livestock.

Much of the escaped nitrogen turns into nitrous oxide, a gas roughly 300 times more potent than carbon dioxide over a century. It also sticks around in groundwater, threatening drinking supplies.

Limiting such runaway nitrogen is therefore a climate fix and a public health tool rolled into one. The new wheat strategy aims to deliver both wins without demanding new chemicals.

Soil and rain waste nitrogen

Soil bacteria convert ammonium fertilizer to nitrate in a two-step process called nitrification. Nitrate is easily washed out of topsoil during heavy rain.

Synthetic nitrification inhibitors slow that conversion but cost money and sometimes harm non-target microbes. Farmers who skip them lose fertilizer, farmers who use them gain new headaches.

Plants themselves can make natural inhibitors, yet breeders seldom tracked that trait because measuring it was hard. Advances in metabolomics now let scientists rank cultivars by their native stopping power.

By leaning on this built-in defense, growers can cut fertilizer bills and still meet yield wheat targets. The trick lies in choosing the right variety for each field.

Wheat microbes manage fertilizer

Researchers describe the plant and its microbes as a holobiont—a single ecological unit shaped by cooperation and conflict. The idea rewrites the usual breeder’s focus on plant genes alone.

Root-zone bacteria help wheat pull in nutrients and fend off disease. In return, the plant feeds them with sugars and signaling chemicals.

Those chemicals, known as root exudates, differ from line to line. Some invite helpful microbes, some chase away pests, and a lucky few block nitrifying species outright.

Mapping this chemical chatter gives breeders new knobs to turn. It also explains why one cultivar thrives in worn-out soil while its neighbor languishes.

Wheat roots release defenses

“Our analysis of root exudates, complicated compounds released from the root system, shows substantial variation between the wheat cultivars,” said Arindam Ghatak, a molecular biologist at the University of Vienna.

The Vienna team screened dozens of elite wheat lines and found a tenfold spread in biological nitrification inhibitor activity.

Lines that topped the chart needed far less ammonium to reach the same biomass as standard checks. Early wheat field trials in Austria and India showed fertilizer savings of up to 30 percent after one season.

One compound under the spotlight is brachialactone, first spotted in tropical forage grass and now turning up in high-BNI wheat. Its structure resembles synthetic inhibitors but degrades harmlessly in soil.

The discovery hints that other cereals might hide similar chemistry. Screening maize and barley is already underway.

Wheat that boosts yield

Tracking subtle root chemicals across thousands of lines calls for heavy analytics. That is where machine learning steps in.

Algorithms sift metabolite fingerprints, microbiome profiles, and yield logs to flag the best genetic combos. The approach turns a breeder’s notebook into a prediction engine.

“In combination with machine learning algorithms, this opens up a promising breeding platform to develop new crop varieties,” said Weckwerth. His group feeds its models with “panomics” data covering DNA, RNA, proteins, and metabolites. 

Once the math nominates winners, rapid cycle crossing and greenhouse trials can push a candidate from Petri dish to field plot within three years. That is half the time of classical pipelines.

Benefits for farmers and the planet

A 25 percent cut in fertilizer on the world’s 540 million acres of wheat would save roughly 12 million tons of nitrogen each year. That translates to billions of dollars and a sharp fall in nitrous oxide.

Lower inputs also mean fewer energy hungry trips by tractors and fertilizer plants. The chain reaction trims carbon emissions well beyond the farm gate.

Health agencies welcome cleaner groundwater and smaller dead zones in lakes. Lake Erie’s algae bloom plan, for instance, banks on a 40 percent nutrient reduction by 2025.

When farmers see yield bumps alongside environmental credits, adoption moves faster. The holobiont approach gives them both carrots.

Greener wheat on the way

The first BNI-rated wheat could reach European seed catalogs by 2028 if regulatory reviews stay on schedule. Asia and North America are likely to follow soon after.

Future projects will probe whether stacking multiple BNI genes with drought-tolerance alleles offers an even sturdier crop. The team is already testing double-stack lines in controlled drought chambers.

Beyond wheat, sorghum, rice, and pasture grasses show promise as self-policing nitrogen users. Each carries its own microbial entourage ready for tuning.

Breeding plants and microbes together might feel unfamiliar today, yet it mirrors how ecosystems have worked for millions of years. The field’s next harvest could be resilience itself.

The study is published in the journal Trends in Plant Science.

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