Deborah Comstock Addressing Poor Water Quality Through Nitrogen Management

Deborah J. Comstock

Nitrogen is not a glamorous subject, but it is essential for plant and food growth. Without it, crops would be vulnerable to climate change, such as drought or excessive rain, and would not produce the amount of food needed to feed this country and the world.

But nitrogen and, more specifically, the use of commercial nitrogen-containing fertilizers is a controversial issue. This is because too much nitrogen in soils has undesirable consequences, such as runoff into streams, groundwater, and large rivers resulting in poor water quality, or water so polluted that ‘it is not sustainable for human consumption.

Fertilizers used in agriculture are an important source of nitrogen in soils. However, nitrogen is also atmospheric, and additional amounts come from animal waste, sewage, and organic matter. It is removed from soils by crops, gaseous losses, runoff, erosion and leaching. Nitrogen must be broken down, a process called “mineralization” before the plant can use the necessary nitrogen. The process or chemistry of nitrogen looks like this:

Most of the nitrogen in the soil comes from N2 gas. This form cannot be used until it is replaced by the ammonium, NH4+ or NO3 forms. There are three important methods for converting nitrogen gas into the necessary forms of ammonium. These include free-living N2-fixing bacteria; N2-fixing bacteria in nodules on the roots of leguminous plants; and nitrogen fertilizer production plants. Nitrogen enters soils in many forms, but eventually turns into inorganic nitrate (NO3-), which can be used by plants.

The problem lies when farmers need to assess the amount of nitrogen needed to grow a productive crop. This is a tough decision tree because nitrogen isn’t just applied to soils, it’s, as mentioned, widespread in our atmosphere and makes up 79% of the air we breathe, according to Texas. A&M AgriLife Extension Service. If plants don’t use all the applied and atmospheric nitrogen, then it escapes, explaining why our streams, groundwater and lakes are negatively affected.

Scientists may have a solution. According to research cited in Anthropocene Magazine, a wheat plant has been developed that can curb nitrogen pollution, potentially preventing greenhouse gases from entering the atmosphere. According to Emma Bryce, author of the recent paper, “scientists based their research on a body of work that explored the ability of certain plants to secrete compounds from their roots and to control certain aspects of the behavior of soil microbes” .

This characteristic, called “biological inhibition of nitrification” (BNI), is linked to a particular chromosomal segment in the genes of certain plants such as wild rye. The researchers then extracted the relevant genetic sequence from the wild rye plants and reproduced it in a common wheat cultivar.

Through laboratory experiments, the researchers discovered that the modified wheat plants were able to reduce the presence of polluting nitrates in the soil by 30%. Additionally, they found that emissions associated with fertilizers were also reduced, with nitrous oxide emissions decreasing by 25%. In other words, the modified wheat plant improved the absorption of nutrients from the fertilizer, leaving more substances intact to absorb.

Wheat is a major crop for this country and the world. If farmers used these pollution-control varieties, it could significantly reduce the greenhouse gas footprint of agriculture and improve the quality of our damaged waterways for future generations.

Deborah J. Comstock is a small farm owner in Adrian and a member of Lenawee Indivisible.

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