Katy Dynarski, PhD - - Soil Health

Dead Zone Cleanup Efforts Mean Better Yields for Farmers

During the summer, oxygen levels in a large area of water in the Gulf of Mexico, off the coast of Louisiana, drop so low that the water can no longer support aquatic life. This lifeless area (aptly referred to as a dead zone) was once a productive fishery; now, starved for oxygen, fish must migrate or die. The Gulf dead zone first appeared in the 1970s and now spans more than 8,700 square miles—larger than the state of New Jersey.

Researchers have identified nutrient pollution, mainly from agricultural and industrial runoff, as the primary culprit behind dead zone formation. In healthy ocean waters, the growth of photosynthesizing algae at the ocean’s surface is limited by nutrient supply. However, nitrogen and phosphorus-rich runoff can act as a fertilizer for algae, allowing populations to explode and form dense mats on the ocean surface. These mats—also known as algal blooms—block light to water below, which cause oxygen levels in the water to plummet until most living things can no longer survive.

Today, growers in the Mississippi River basin are at the forefront of tackling this environmental challenge through management practices to reduce agricultural nutrient pollution. Through these efforts, they are discovering that environmental stewardship also boosts the health and profitability of their farms.

Creation of a Dead Zone

Beginning in Minnesota and eventually flowing into the Gulf of Mexico in Louisiana, the Mississippi River drains 41 percent of the land area in the United States. Much of that land is agricultural, and nutrients from excess fertilizers can wind up in waterways that ultimately pour into the Mississippi.

"Over time, nitrogen has built up in the environment—in soils and in groundwater," explained Kim Van Meter, a scientist at the University of Waterloo who studies the dead zone. "Nitrogen that we see today in the Mississippi is in many cases not the nitrogen that was applied to crops this year, but nitrogen that has been slowly making its way through the landscape for decades."

By the time the river drains into the Gulf, more than 2,000 miles from where it began, it is laden with nutrients, particularly nitrogen, which support the growth of off-shore algal blooms. The resulting oxygen-depleted waters have damaged key industries in the Gulf such as shrimping and tourism, costing an estimated $82 million per year in lost profits.

Nitrogen that we see in the Mississippi today is nitrogen that has been slowly making its way through the landscape for decades.

Turning the Tables

Revitalizing the dead zone means dramatically reducing the amount of nutrients reaching the Gulf. With that in mind, the Natural Resource Conservation Service launched the Mississippi River Basin Healthy Watersheds Initiative (MRBI), a voluntary program that helps growers and other land managers across 13 states contribute to stewardship in the Mississippi River Basin. The program provides incentives and support for growers to adopt a variety of practices to reduce their fertilizer inputs, prevent sediment loss from their fields, and decrease nutrient runoff into surrounding waterways.

This community-driven approach has been successful at both a national and a local level. Since the program’s inception in 2009, growers' efforts have resulted in an overall reduction of 9.5 million pounds of nitrogen and 2.85 million pounds of phosphorus entering the Gulf from the Mississippi River. Locally, the program has also resulted in cleaner drinking water, nitrate levels are dropping in watersheds with participating growers, and rivers and streams that were once considered “impaired” are now being removed from state listings.

Improving Water Quality and Building Soils

The same conservation practices that make water cleaner also contribute to soil health, as Tim Smith discovered on his 800-acre corn and soybean farm in Wright County, Iowa. With help from a conservation planner, he came up with a nutrient management plan to drastically reduce his fertilizer use, reduced his tillage to control soil erosion, and planted cover crops to trap any applied nitrogen that wasn’t being taken up by his cash crops.

Two years later, the nitrate levels in the water leaving Smith’s farm were less than half of what they used to be, indicating that his practices were working.

But Smith also found that his efforts to contribute to water quality in his local watershed were building up the health of his soils. Using cover crops and less tillage led to the accumulation of more soil organic matter, and Smith noticed visible changes like more earthworm activity in his soils and more developed crop root systems. “Healthier soil long-term means more crop sustainability and better yields with fewer inputs,” he noted.

In Illinois’ Indian Creek watershed, Jim Ifft has reduced tillage and implemented cover crops on his corn, soybean, and wheat farm through MRBI and seen similar successes. With the new practices, Ifft’s soils grew healthier, resulting in deeper crop roots and better water infiltration. He’s saved money by not having to apply as much fertilizer and herbicides, as well as spending less time and labor to till his fields. And, his soybean yields have increased by three bushels an acre.

The same conservation practices that make water cleaner also contribute to soil health.

Profitable Stewardship

Although bringing the Gulf dead zone back to life remains a serious challenge, the success of MRBI on both local and national levels shows that the actions of individual growers can have far-reaching environmental benefits. Fertilizer management and other soil conservation practices have led to improved water quality in small watersheds, as well as a dramatic decline in the amount of nutrient runoff that reaches the Gulf.

Best of all, growers can combine conservation pracrtices with economic success. The same practices that contribute to clean water—both near and far—also build up healthy farm soils, resulting in increased profits for growers.

For Jim Ifft, the opportunity to practice profitable stewardship is energizing, and he often hosts field days to share his strategies with nearby farmers. Thanks in part to his education efforts, 60 percent of the landowners in Ifft’s watershed are now implementing similar conservation practices, and Ifft believes that they’ll all see benefits for both their environment and their pocketbooks.

“We want to make money, but we also want to leave the land better than we found it,” Ifft explained.