Iowa has lost half its topsoil since 1850 and most of ITS REMAINING organic matter has been heavily depleted.

by Justin and Britney

On this test plot, a cover crop of winter rye was planted at the end of harvest to keep the soil covered. The adjoining plot was left bare. Exposed soil is susceptible to erosion and depletion. In fact, Tom’s research shows that cover crops like winter rye increase soil organic matter while reducing or even reversing soil depletion trends. Adding more diverse crops also lets the soil heal a little bit more every year.

SOIL DEPLETION

The removal of nutrients, biological diversity, or structural quality due to improper cropping practices.

COVER CROP

A plant grown primarily to manage soil erosion, water, suppress weeds, build soil organic matter, and control diseases and pests. They are usually grasses or legumes but may also be comprised of other green plants. It may also be used to help prevent nutrients from leaching into local waterways.

SOIL ORGANIC MATTER (SOM)

Before forests and grasslands were converted to field agriculture, soil organic matter generally composed 6 to 10% of the soil mass, well over the 1 to 3% levels typical of today’s agricultural field systems. SOM consists of carbon compounds formed by living organisms in various stages of decomposition They could be lawn clippings, leaves, stems, branches, moss, algae, lichens any parts of animals, manure, sawdust, sewage sludge, insects, earthworms and microbes. Benefits include greater water retention capacity (which can reduce nutrient leaching) and enhanced microbial biodiversity.

“Five hundred years from now we might realize that we shouldn’t have been farming this way,” LEE TESDELL OBSERVES. “We’re in this agricultural system that has some built in problems and We’re leaving it all for future generations to figure out.”

by Maxwell, Alyssa and Megan

NUTRIENT SEQUESTRATION

Retaining nutrients like nitrogen and phosphorous in the soil means keeping them available for next year’s crops while reducing agricultural runoff that could degrade water quality downstream.

CARBON SEQUESTRATION

Some agricultural practices, including no-till and the use of cover crops, can help mitigate the negative effects atmospheric carbon dioxide has on our climate by capturing and storing atmospheric carbon dioxide in the soil.

COVER CROPS

Help eliminate fall tillage, increase soil organic matter, keep soil covered, and furnish forage for livestock during thewinter.

“If we leave the farm bare, those nutrients will run into the water and contribute to its degradation.”

LEE TESDELL
Family Farmer
Tesdell Century Farm
South of Slater, IA

EVERYBODY SHOULD HAVE THE RIGHT TO CLEAN DRINKING WATER.

by Derek, Lena and Mike

“I believe citizens have responsibilities to their waterways. We, as citizens, ought to support regulations that make sure our water is clean. We need to establish criteria. Right now, we have only one criteria, and that’s just for nitrate levels in drinking water. There’s no rule for phosphorus, there’s no rule for bacteria except on swimming beaches.”


ERV KLAAS
Professor Emeritus of Animal Ecology
Iowa State University
Ames, IA

IOWA CODE CHAPTER 455B

Protects water quality and focuses heavily on setting water quality standards and designated uses and expectations for water. Volunteers help raise awareness and regulate the issues surrounding water and nitrate levels, laid out by the Iowa Code.

CAN PLANT SCIENTISTS HELP FARMERS ADOPT FARMING PRACTICES THAT MAXIMIZE THE BENEFITS OF NITROGEN FERTILIZER WHILE REDUCING THE THREAT OF CONTAMINATING GROUNDWATER?

by Derek, Lena and Mike

Farmers can document the benefits of applied fertilizer by establishing a nitrogen budget to track nutrients entering and leaving a field. Nitrogen can be added with fertilizer, through irrigation water, residual plant-available nitrogen already in the soil, from legumes that fix atmospheric nitrogen, from the decomposition of plant and animal residues, and from the mineralization of soil organic matter. Conversely, nitrogen can be lost though leaching and denitrification, and in the case of manure or urea-containing fertilizers lost into the air through volatilization.

Precisely timed fertilizer applications and carefully managed water use can allow commodity crops like corn to uptake most of the available nitrogen in the soil through its roots. After a corn or soybean harvest, when there are no live plant roots in the soil, water moving downward can carry soluble nitrogen into drainage tiles or groundwater. Incorporating the off-season planting of legumes and cover crops like winter rye into corn and soybean rotations allows these nutrients to be taken up in the soil, thereby reducing agricultural runoff.

NITROGEN BUDGET

        Keeping track of nitrogen in the soil.

“How do we keep track of our nitrogen budget? The answer is “not very well”, but we are making attempts to measure it as best we can, and what we learn from our research helps us understand how and when nitrogen is lost.”


DR. TOM KASPAR
Plant Physiologist
USDA/ARS
Ames, IA