WSUV researcher works to help plants absorb nitrogen from air

Nitrogen makes plants grow. It’s a fundamental building block for all living things, essential for the creation of proteins, amino acids and chlorophyll.

Commercial farmers typically must rely on synthetic nitrogen fertilizers to add nitrogen back into the soil. Despite making up 78 percent of our planet’s atmosphere, plants cannot directly absorb nitrogen from the air.

But what if they could? Associate professor Stephanie Porter from Washington State University Vancouver is working to make that possible.

“We like to look at wild plants and look at the adaptations that have evolved there over a long time periods and see how we might apply some of these useful adaptations to help crops grow better,” Porter said.

Last month, Porter published her research on transferring genes from rhizobia bacteria found in legumes, particularly peas and beans, that absorb nitrogen from the air into bacteria that do not. She and her team worked with commercial farmers on a proof-of-concept solution they hope will transfer to other crops.

“Our research is about how microbes can take and harvest nitrogen from the air using a suite of genes that work really well in a bacterium but are hard for other organisms to accomplish,” she said. “We’re trying to emphasize this more natural pathway for getting nitrogen to crops.”

In the research paper published in May, the team describes how to convert regular bacteria that can’t harvest nitrogen for plants into ones that can in a single step. Some of the difficulty, Porter said, has been that mating one rhizobia that can harvest and transfer nitrogen into a bacterium that can’t is very rarely successful.

“We developed a new technique to transfer this ability,” she said. “We developed a system, a genetic technique where we can detect when it is successful and access those successful transfer events. So then we can, at a much higher throughput, generate these transfers, essentially creating new nitrogen-fixing bacteria from lineages.”

Porter, who has been working and teaching at WSU Vancouver since 2015, said reducing the need for synthetic nitrogen would benefit both farmers and the environment.

Producing synthetic nitrogen fertilizer involves a complex chemical process that is very fuel intensive. The process involves extracting nitrogen gas directly from the air and bonding it with hydrogen derived from fossil fuels, typically natural gas, at extreme temperatures and pressures to produce anhydrous ammonia. While the ammonia gas can be used as-is for deep soil injection, it is often processed further into solid or liquid fertilizer.

“It’s a costly process monetarily and environmentally. That’s why being able to harness this nature-based solution where bacteria are performing this process without those kinds of economic and environmental costs is really attractive,” Porter said.

For other crops, such as wheat, barley or corn, finding a solution won’t be as straightforward. While they are heavy nitrogen feeders, grasses like wheat don’t have the same kind of symbiosis to produce nitrogen for themselves with bacteria as beans and peas have, Porter said.

“Other labs have made these cool, exciting discoveries that they can start to make the kinds of root structures that allow things, like barley, to house these bacteria. Our idea, since we’re working on the bacteria side, is once those people figure that out, we would like to have symbionts (different species that live together in a close, physical or biological association) already generated that could help them take the next step,” she said.

Clark County Council Chair Sue Marshall, who is also a farmer, is interested in future applications of Porter’s research. Marshall and her husband, Rob Baur, co-own Baurs Corner Farm in Ridgefield, a 27-acre farm that primarily grows hazelnuts.

“I would wonder on what scale this could be useful? I’m thinking of the commodities, like corn and wheat and things like that,” Marshall said.

Nitrogen does play an important role in keeping their 3,100 hazelnut trees productive, she said. Her farm recently applied fertilizer to those trees.

“Maintaining nutrients in a sustainable way so you’re not depleting a limited resource like fossil fuels is a very good thing,” she said.

La Center farmer Val Alexander of Coyote Ridge Ranch is also interested in where Porter’s research could lead.

“We are always interested in the latest research to assist our organic farming practices. We have had researchers from WSU many times in the past studying various techniques which assist plant development and wildlife protection,” she said.

Alexander’s 65-acre farm grows a wide variety of crops, everything from tomatoes, peppers and corn to apples, pears and plums. In the winter, she grows cover crops like red clover and field peas, which are cut and tilled into the soil to feed the summer crops. She said she also uses compost and chicken manure, which has high levels of nitrogen, direct from her chicken coop.

“Tilling in the cover crops seems to add the right amount of elements for most crops,” she said.

As for her research, Porter is ready to move onto the next step and apply it to other crops. In Washington, where more than $2 billion in wheat is grown each year, reducing demand for synthetic nitrogen would fit well with the state’s climate goals.

“Currently, most of the nitrogen we need to grow that wheat is from synthetic fertilizers,” she said. “This is a widespread agricultural concern. If we can make any improvements, they’re very scalable and directly target a need.”

Porter said there are a lot of exciting developments in her research field, work she wants to bring back to Washington.

“The more we can get ahead and have these more sustainable approaches that could be quite scalable. I feel very motivated to be part of that process,” she said.

She said she sees a lot of potential to make things work even better than they already do.

“I want to team up and collaborate with some other labs across the United States to try and use this process we’ve developed much more broadly,” she said. “We’re not going to make that Nobel Prize breakthrough, but we’ve taken one step toward this process.”