With an ever-increasing world population to feed, staple foods like legumes are only going to become more important. Researchers at Washington State University (WSU) have developed a method to make soybean plants grow larger and produce significantly more seeds by kicking their ability to pull vital nitrogen from the air into overdrive. If applied to other legumes, the technique could not only increase crop yields, but also reduce the need for nitrogen fertilizers and make for more drought-resistant plants.

Nitrogen is a key nutrient for plants, but while most source theirs from the soil through their roots, legumes have a unique ability to "fix" or convert it from the atmosphere. The process of "fixing" the gas from the air comes courtesy of a symbiotic bacteria known as rhizobia in the plant's root nodules, which not only feed the plant itself but increase the nutrient's concentration in the surrounding soil.

In order to beef up their soybeans, the WSU team first beefed up the number of proteins that carry nitrogen from the root nodules up to the plant's leaves and seeds. With more proteins, nitrogen was transported around the plant faster, which in turn triggered the bacteria to fix more nitrogen from the atmosphere, resulting in larger plants with up to 36 percent more seeds than unmodified soybeans.

"They are bigger, grow faster and generally look better than natural soybean plants," says Mechthild Tegeder, lead researcher on the study. "Some evidence we have suggests they might also be highly efficient under stressful conditions like drought."

Apart from the obvious benefit of increased yield, the technique may help solve the logistical issue of providing crops with enough nitrogen to thrive. Synthetic nitrogen fertilizers are often used to bolster plant productivity, but production, transportation and use of these carry high costs and environmental impact, and a lack of availability in developing countries can limit food production in those areas.

"The biggest implication of our research is that by ramping up the natural nitrogen allocation process we can increase the amount of food we produce without contributing to further agricultural pollution," says Tegeder. "Eventually we would like to transfer what we have learned to other legumes and plants that humans grow for food. Our research also has the potential to be transferred to other crop plants that don't fix nitrogen from the atmosphere but would benefit from being able to uptake nitrogen more efficiently from the soil."

The research was published in the journal Current Biology.