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3 Ways Nitrogen Researchers Are Advancing Agriculture

By Michael Udvardi, Ph.D.
Chief Scientific Officer

Posted Mar. 1, 2018

Ammonia was described as the "detonator of the population explosion" of the 20th century by scientist Vaclav Smil, Ph.D.

Most nitrogen (N)-containing fertilizers are derived from ammonia synthesized via the Haber-Bosch process, which is arguably the most important technological innovation of the 20th century. Without synthetic N-fertilizers, half of the world population would go hungry. Today, more than 100 million tons of N-fertilizer is used by agriculture each year, which has doubled the amount of reactive-N in the global biogeochemical N-cycle. Losses of reactive-N from agriculture, through leaching to aquifers, rivers, lakes and oceans, and gaseous losses to the atmosphere, have huge impacts on the environment and human health. The so-called "dead zone" in the Gulf of Mexico, which forms in summer as the result reactive-N and other nutrient losses into the gulf, is one of many such impacts. Thus, nitrogen fertilizers are both a blessing and a curse to society.

A large fraction (70 to 80 percent) of agriculture in the Southern Great Plains is dedicated to forage-based beef cattle production, which is generally low-input in terms of fertilizers and water (most forages are rain-fed). Thus, nitrogen fertilizer inputs to forage production are typically less than one-third of what is used on other food crops. Nonetheless, an average of 50 percent of the nitrogen applied to pastures is not captured by the plants in the application year and is subject to loss into the environment. This represents an economic loss to ranchers in addition to costs to human health and the environment, which are harder to quantify.

The Noble Research Institute aims to increase the efficiency of nitrogen use in forages and other agricultural systems through research development and demonstration.

1. Improve Legumes

First, plant biologists and breeders are working to improve legumes, such as alfalfa, to make them better adapted to the Southern Great Plains. Legumes are relatively unique amongst plant species because they don't need nitrogen fertilizer to grow. Legumes can make their own ammonia through symbiosis with nitrogen-fixing bacteria. Soil bacteria called rhizobia are able to live in legume cells within organs called root nodules, where they convert atmospheric di-nitrogen (N2) into ammonia (up to several hundred pounds per acre per year). Virtually all of this ammonia is used for plant growth, with relatively little being lost to the environment. Thus, symbiotic N-fixation in legumes such as alfalfa is sustainable, environmentally friendly and almost free (apart from the small cost of rhizobia applied to seed or soil at planting). Greater use of legumes would help to increase N-efficiency of, and reduce N-losses from, agriculture in the Southern Great Plains.

2. Identify and Breed Plants That Are More Efficient Nitrogen Users

Researchers at the Noble Research Institute are also working to identify plants that are better able to capture and utilize nitrogen fertilizer applied to the soil. Some plants have superior root systems that are better able to explore the soil and/or take up N-compounds from the soil, while other types may be more efficient at absorbing that nitrogen for growth and protein production. By mating plants that are best at capturing soil nitrogen with ones best at utilizing such nitrogen for shoot growth, our plant breeders aim to develop N-efficient plant varieties that contribute to productive forage systems that lose less fertilizer to the environment. This will improve profitability and environmental stewardship of operations across the country.

3. Develop Grasses That Fix Nitrogen

In a third approach, the Noble Research Institute, together with collaborators in the United States and United Kingdom are working to develop N-fixing symbioses in grasses. Grasses rely on mineral-N in the soil for growth, which is typically replenished with fertilizer-N. However, like all plants, grasses harbor bacteria in their root systems, typically between root cells. Some of these bacteria have the potential to change atmospheric di-nitrogen into ammonia in the same way that rhizobia do in nodules. We believe it may be possible to increase the numbers of such endophytic bacteria in grass roots and trigger them to fix nitrogen and release ammonium to surrounding plants cells. We aim to supply half the nitrogen needed by grasses in this way.

Ideally, we would like to eliminate the use of industrial N-fertilizers altogether for a more sustainable and environmentally-friendly agriculture. Clearly, we have big dreams. But we also have great scientists. So watch this space!

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