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Growing cereal crops with less fertilizer
Discovery could reduce nitrogen pollution, save farmers billions
Researchers at the University of California, Davis, have found a way to reduce the amount of nitrogen fertilizers needed to grow cereal crops. The discovery could save farmers in the United States billions of dollars annually in fertilizer costs while also benefiting the environment.
The research comes out of the lab of Eduardo Blumwald, a distinguished professor of plant sciences, who has found a new pathway for cereals to capture the nitrogen they need to grow.
The discovery could also help the environment by reducing nitrogen pollution, which can lead to contaminated water resources, increased greenhouse gas emissions and human health issues. The study was published in the journal Plant Biotechnology.
Nitrogen is key to plant growth, and agricultural operations depend on chemical fertilizers to increase productivity. But much of what is applied is lost, leaching into soils and groundwater. Blumwald's research could create a sustainable alternative.
“Nitrogen fertilizers are very, very expensive,” Blumwald said. “Anything you can do to eliminate that cost is important. The problem is money on one side, but there are also the harmful effects of nitrogen on the environment.”
A new pathway to natural fertilizer
Blumwald's research centers on increasing the conversion of nitrogen gas in the air into ammonium by soil bacteria — a process known as nitrogen fixation.
Legumes such as peanuts and soybeans have root nodules that can use nitrogen-fixing bacteria to provide ammonium to the plants. Cereal plants like rice and wheat don't have that capability and must rely on taking in inorganic nitrogen, such as ammonia and nitrate, from fertilizers in the soil.
“If a plant can produce chemicals that make soil bacteria fix atmospheric nitrogen gas, we could modify the plants to produce more of these chemicals,” Blumwald said. “These chemicals will induce soil bacterial nitrogen fixation and the plants will use the ammonium formed, reducing the amount of fertilizer used.”
Blumwald's team used chemical screening and genomics to identify compounds in rice plants that enhanced the nitrogen-fixing activity of the bacteria.
Then they identified the pathways generating the chemicals and used gene editing technology to increase the production of compounds that stimulated the formation of biofilms. Those biofilms contain bacteria that enhanced nitrogen conversion. As a result, nitrogen-fixing activity of the bacteria increased, as did the amount of ammonium in the soil for the plants.
“Plants are incredible chemical factories,” he said. “What this could do is provide a sustainable alternative agricultural practice that reduces the use of excessive nitrogen fertilizers.”
The pathway could also be used by other plants. A patent application on the technique has been filed by the University of California and is pending.
Dawei Yan, Hiromi Tajima, Howard-Yana Shapiro, Reedmond Fong and Javier Ottaviani from UC Davis contributed to the research paper, as did Lauren Cline from Bayer Crop Science. Ottaviani is also a research associate at Mars Edge.
The research was funded by the Will W. Lester Endowment. Bayer Crop Science is supporting further research on the topic.
Editor's note: Blumwald is affiliated with UC Agriculture and Natural Resources through the Agricultural Experiment Station at UC Davis.
What makes food grow - and why that matters
There’s a lot of attention paid to where food comes from nowadays. Less attention has been paid to what helps that food grow, but that’s an important part of the equation. Whether organic or conventionally grown, the tomatoes, lettuce, plums and other food we eat rely on nutrients in order to grow. One of the most important nutrients for plant productivity is nitrogen.
Nitrogen, which is ubiquitous in our atmosphere in a relatively inert, gaseous form, is not available to most plants unless it is transformed into a reactive form and added to soil, where plants can use it to grow. Most often nitrogen is applied to fields in the form of synthetic fertilizer, although organic production relies on other nitrogen sources, such as cover crops, manure, fish meal and poultry waste.
Agricultural production depends on nitrogen in order to grow reliable, high yielding crops. But this nitrogen, when it is applied to fields in the reactive form that plants can use, also tends to leak out into air and water and cause pollution when all the nitrogen applied to the field is not used up by the plants.
The California Nitrogen Assessment, a project of the Agricultural Sustainability Institute at UC Davis, is taking a hard look at the whole system of nitrogen use in California. While nitrogen is hugely important to producing the food and fiber that we all need, there may be ways to use it more efficiently and reduce the pollution problems it can cause. These problems include air and water pollution, which can have negative consequences for human and environmental health in California.
Since nitrogen is so important to producing the food that all of us eat, the Agricultural Sustainability Institute’s team has involved stakeholders from all around the agricultural system. The assessment team has sought insight from farmers and economists, policy makers and public health groups, and Californians whose drinking water has been polluted by nitrogen, forcing them to buy bottled water on a regular basis. There are many diverse perspectives and ideas about how nitrogen should be managed in California’s future. The assessment will provide a synthesis of the most up-to-date scientific knowledge on science, policy and practice to inform decision making on how to improve nitrogen management.
Thinking about where food comes from is one important part of understanding the food system. Learning about the trade-offs involved in other key agricultural inputs is another.
Find out more about nitrogen and the California Nitrogen Assessment at its website. If you are interested in becoming involved in the assessment as a stakeholder participant, visit the website for more information to learn how you can get involved.
