Corn is an ancient crop, and despite the prevalence of “No. 2 yellow corn,” there are numerous and diverse grain corn varieties that hold promise of environmental benefits and improved nutritional quality for livestock and people.

With the help of a small corn breeding organization, a group of Pepin County, Wis., farmers has been testing unique corn in a quest to reduce nitrate contamination of groundwater. What they are discovering is that some corn varieties have improved nitrogen efficiency and traits that reduce nitrate loss to the environment. In addition, this corn can provide increased levels of protein — methionine, in particular — and various trace minerals that are important for livestock and human health.

Brief history of modern corn

Corn has been around for millennia. The indigenous peoples of the Americas developed it from a wild grain called teosinte, and over the course of thousands of years bred it for various purposes — for example: field, flour, pop and sweet corn. These different corn types were adapted to regional soils, climates and moisture conditions ranging from South America to the modern Corn Belt of North America. Today, corn is the largest grown crop in the U.S., but it’s commodity form as No. 2 yellow corn is a rather recent development.

Hybrid breeding methods in the early 20th century brought uniformity to corn, and an ability to convert mineral fertilizer into ever-increasing yield. The explosion of yield potential, however, brought inadvertent side effects. Modern breeding practices usually provide ideal fertility conditions so that exceptionally yielding genetics can be observed and selected.

The downside to this approach is that more resilient traits — such as genetics that help the corn to grow under stressed or less-than-ideal conditions — may inadvertently be bred out. For example, Illinois researchers reported that since the 1960s, while corn yields have steadily increased, the size of the plant’s root system has decreased. While this may be irrelevant under ideal fertility and moisture conditions, during a stressful growing season, these shortcomings may lead to critical loss in yield.

The researchers also found that these standard hybrid corn varieties had fewer soil microbe partners on its roots. Like the microbes in the human or animal digestive system, plant root microbes are important to the plant’s nutrition and overall health. Certain microbes naturally assist nitrogen acquisition and stabilization, even for non-legume plants.

Corn partners

Legumes are known as “nitrogen fixers,” although this is not technically correct. It is the legume’s microbial partner, rhizobia bacteria, that are the actual nitrogen fixers. The legume provides the environment, in the form of visible root nodules, in which the bacteria have the right environment to convert nitrogen from the air to plant-usable nitrogen. Other non-legume plants, including corn, have been found to develop microbial partnerships, but in a more subtle way.

Like any lasting partnership, when work is shared, profits are also shared. When bacteria provide nitrogen to a plant, it takes energy. So, in exchange for the nitrogen provided by the bacteria, the plant provides sugars — the product of photosynthesis — to the bacterial partners. These partnerships are the focus of corn breeding efforts to reestablish the corn-microbe connection within modern varieties.

Interestingly, it has been discovered that certain corn carries its important bacterial partners in the seed. When the seed sprouts, these bacteria are transferred into the surrounding soil. Once established in the root zone, some microbes fix nitrogen, while others acquire hard-to-get minerals, encourage root growth or provide immune assistance for the corn against disease.

Farmers testing these corn varieties hope they can reverse the trend of nitrate contamination of groundwater. Perhaps more importantly, restoring these natural partnerships between corn and microbes will build a more sustainable production system. As we help corn to reconnect with the natural partners it has known for thousands of years, perhaps it will continue to provide the yield we desire while helping us achieve the water quality we need.

Travis is the University of Wisconsin Extension agriculture and natural resources educator for Pierce and Pepin counties.