PULLMAN, Wash. – Michael Kahn, a fellow in Washington State University’s Institute of Biological Chemistry and associate director of the Agricultural Research Center, has received a three-year $510,000 grant from the U.S. Department of Energy’s Energy Biosciences Program to continue fundamental research that may someday reduce farmers’ reliance on an increasingly expensive farm input: industrially produced nitrogen fertilizer.
“Nitrogen fertilizer is the single biggest expense that many farmers incur in raising their crops,” said Kahn. “It is made directly from natural gas, so when the price of natural gas rises, so do fertilizer prices. In addition, we don’t manufacture much of the fertilizer in the United States. Last year, we imported about 70 percent of the nitrogen fertilizer we used.”
Anhydrous ammonia prices doubled from $250 a ton in 2002 to over $500 a ton last year, according to Kahn. “Some people speculate that they might rise to $1,000 a ton due to increased energy prices, the weakness of the dollar and demand in other countries.”
Legume crops, such as alfalfa, peas, lentils, soybeans and chickpeas, form symbiotic relationships with bacteria in the soil and through a complex relationship fix nitrogen gas from the air into ammonia, which the plants can use for growth.
The goal of Kahn’s research is to improve the nitrogen productivity of legumes to produce more nitrogen for subsequent crops and perhaps to transfer nitrogen fixation to other crops, such as grains that can’t currently fix nitrogen.
“The bacteria invade the plant roots, and the symbionts feed each other,” Kahn said. “The plant gives the bacteria carbon compounds that they can use to generate energy, and this energy is then used to fix nitrogen. The bacteria gives the plant the ammonia that results.”
A signaling pathway precedes the development of that relationship. “Chemicals go back and forth between the bacteria and the plant,” he said. “What people have not understood is that when fixation is happening, are there signals going back and forth that coordinate those activities?”
Kahn and his collaborator Svetlana Yurgel, a research assistant professor in IBC, have discovered a bacterial mutant that may help answer that communications question.
“The mutant that we isolated has very peculiar behavior,” Kahn said. “It fixes nitrogen at what appears to be normal or higher than normal rates, but the plant doesn’t get green. We are very sure of the phenomena. We’re just not sure of the explanation. It’s something very different from what I would have speculated two years ago, and I think it is what has gotten people excited about the work we proposed to do.”
If manipulating the circuit disrupted in the mutant made it possible to store some of the nitrogen fixed by the bacteria and simultaneously feed the plant, the total amount of nitrogen fixed might increase. Subsequent crops could use this nitrogen instead of industrially produced fertilizer, increasing soil fertility and decreasing input costs.
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