Farmers apply nitrogen fertilizer to nourish their crops, but these nutrients often don’t stay in the soil as efficiently as they can and end up being released into the air and water supplies as nitrates and nitrous oxide.
Starting with sorghum, the AgriLife research team at Texas A&M University is working to find crop varieties that minimize nitrogen runoff, reducing farmers’ input costs and greenhouse gas emissions into the atmosphere.
The project is led by Dr. Nithya Rajan, who was recently appointed director of the Center for Greenhouse Gas Management in Agriculture and Forestry. Dr. Rajan is a professor of agronomy and agroecology in the Department of Soil and Crop Sciences in the Texas A&M College of Agriculture and Life Sciences and a crop physiologist with AgriLife Research.
Five years ago, Rajan began his research, “Innovative Sorghum-Based Production Systems with Biological Nitrification Inhibition Properties for Enhanced Agroecosystem Sustainability,” funded by the USDA-NIFA Agriculture and Food Research Initiative – Basic and Applied Sciences program.
She says she and her team are now seeing promising results in developing traits that are good for plants, farmers and the planet.
“The BNI property inhibits nitrification, the microbial process that converts fertilizer-derived ammonium into nitrate in soil, preventing the nitrate from being released into water or as nitrous oxide, a greenhouse gas.”
Nitrification, denitrification, biological nitrification inhibition
Rajan said nitrification and subsequent denitrification promotes nitrogen loss from agricultural land and is the underlying cause of low nitrogen-use efficiency in most field crops and emissions of nitrous oxide, a potent greenhouse gas.
In today’s agricultural practices, producers must pay extra for fertilizers that contain nitrification inhibitors in order to maintain the fertilizer they have applied.
But it has been found that some plants can suppress nitrification by releasing inhibitors from their roots, a trait called biological nitrification inhibition (BNI), she said. The BNI trait helps retain nitrogen in the soil for longer, increasing nitrogen uptake by crops and reducing nitrogen loss primarily as nitrous oxide, the main greenhouse gas emitted from croplands.
Rajan and Sakiko Okumoto, Ph.D., AgriLife Research plant physiologist and associate professor in the Department of Soil and Crop Sciences, selected sorghum genotypes from a sorghum breeding program led by AgriLife Research sorghum breeder and professor, Dr. Bill Looney, Borlaug-Monsanto Chair in Plant Breeding and International Crop Improvement.
Those with BNI properties underwent three years of field testing to confirm reduced nitrogen losses as nitrates and nitrous oxide.
“This is a new research initiative at Texas A&M AgriLife Research, and we’re at the forefront of targeting the development of climate-adapted crops with this trait,” Rajan said. “Our field data shows significant reductions in greenhouse gas emissions. We believe that by developing a climate-adapted sorghum, we can increase fertilizer use efficiency and reduce nitrous oxide emissions.”
Narrow your focus
The grant enabled Okumoto to identify the specific combination of genes responsible for the BNI trait.
“Thanks to support from USDA-NIFA, the Panther RISE grant program funded by Prairie View A&M University and Texas A&M University, the United Sorghum Checkoff Program and the Texas Sorghum Producers Board, we were able to build a model to predict and select lines that are likely to be good,” Okumoto said. “Now we have a clear path to implement and leverage that model in our breeding programs and further improve it.”
The team believes they are only just scratching the surface of what is to come from Looney’s development program and are only just getting started.
“BNI is a genetic trait,” Looney said, “and there is a lot of variation for this trait in the current germplasm pool, which allows for significant improvement of this trait.”
Rajan said it’s important to avoid yield losses, and they want to conduct large-scale field trials in all major sorghum-growing regions to develop best management practices that will tell farmers how much less fertilizer they can apply without incurring yield losses.
Their current data indicates that the action of nitrification inhibitors selectively targets nitrifying microbial populations, with minimal impact on the soil microbiome as a whole. Sanjay Antony Babu, assistant professor at AgriLife Research and soil microbiologist, is investigating the effects of BNI on various soil microbes. This research is essential to ensure soil health, as it relates to microbial diversity, is not adversely affected by BNI.
Bioenergy sorghum is the target crop.
Looney said that in addition to grain and feed sorghum, another target crop that could contain the BNI trait is bioenergy sorghum, a relatively new concept pioneered by Looney’s sorghum breeding lab, AgriLife Research.
Bioenergy sorghum is a special type of sorghum that grows for a long period of time, does not produce grain, is highly drought tolerant and has a high yield of cellulosic biomass, he said.
As with grain and feed sorghum, incorporating the BNI trait should reduce the amount of nitrogen fertilizer needed for production and increase the efficiency of use of applied nitrogen, Looney said.
What’s next?
The ultimate goal, Rajan said, is to develop climate-adapted sorghum, which would not only reduce fertilizer costs but also reduce environmental impacts. Climate-adapted crops could not only allow farmers to earn credits for their practices, but also benefit the environment.
“Nitrogen is essential for food production, but its use can also cause problems,” she said. “Developing crop varieties that are adapted to our climate is a good solution because it can prevent so much nitrogen from being lost to water or as greenhouse gases.”
