Nearly 95% of Iowa’s Wetlands have been destroyed, as a result we lose our natural filters.

Wetlands like Engeldinger Marsh, which was formed by the most recent glacier that covered North Central Iowa about 12,000- 14,000 years ago, have some of the cleanest water in the nation. If we still had its original number of wetlands today, there would be virtually no flooding in the Des Moines are Dikes or levees in Iowa prevent water from coming over the banks and flooding adjacent areas. If they were removed, much of the water would be retained in the wetlands and reduce flooding downstream.

As the vegetation from the marsh, sedges, and other plants are distributed onto the surface of the swamp, they are often covered with water all or part of the year, the water slows the decomposition process. Over time, more and more plant material gathers and forms a layer of peat (partially decayed plant material). This peat layer is the transition between plant material and soil. Eventually the peat breaks down into soil.


Areas on the landscape that remain wet year round or become wet seasonably.

The EPA defines wetlands as “areas where water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. Water saturation (hydrology) largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support both aquatic and terrestrial species. The prolonged presence of water creates conditions that favor the growth of specially adapted plants (hydrophytes) and promote the development of characteristic wetland (hydric) soils.”

Subsurface flow can affect the quality of Iowa’s water if practices allow nutrients in the soil to drain into surface waters.

by Caleb, Swaesy, Sam and Haley

An average acre of corn in Iowa uptakes about 22 inches of soil water per growing season, and requires an average nitrogen concentration in the soil water solution of approximately 44 mg/L NO3-N to produce a high crop yield. That concentration would impair water quality if it is drained by tiles into surface waters. The question is: how can we fertilize crops to get economic yields while keeping NO3-N concentrations in soil water solution below 10 mg/L to meet the drinking water standard?

In the Midwest we hear most often about ‘subsurface flow’ as ‘subsurface drainage’ via tile lines. Tile lines are perforated pipes underneath farm fields that collect water infiltrating the soil and drain it into surface waters downstream. This drainage removes excess water from the soil and gives crops the room and air that they need to grow.


The movement of water in a saturated porous media as a result of gravity or potential energy differences from one location to another.

In order to continue to be able to use his fields John has to use tiling. John is working with the South Fork Watershed Alliance to develop new ways to prevent nutrients from entering the water.

by Maxwell and Alyssa

John doesn’t till his fields. No till practices increase the microbial life in his soil, which increases the soil’s capacity to hold water. If the soil holds more water, less nitrate goes into his tiles. He also makes sure to not over apply nitrate fertilizer so that less nitrate goes to our water and more goes to the production of food. John wants to keep nitrate on the land and out of the water.

Nitrate is water soluble, so when water falls onto a field with nitrate on it, the nitrate will go where the water goes. Water goes into the tiling, taking nitrate with it. Tiling is widely used in agriculture in Iowa.

“Tiles are the same thing as that little hole in the bottom of your flowerpot.”

Gilbert Family Farms
Iowa Falls, IA


A network of pipes installed in the soil to drain water from agricultural areas.


A direct, unrestricted inlet well at ground level that reduces soil erosion and improves surface drainage through underground piping (tiles). An inlet well also allows water to be drained from depressions that are too large to be filled in.

Kris Kohl, a field specialist AT Iowa State University’s Extension Program, helps farmers design their own private drainage systems that connect into larger drainage districts.

by Michael, Alex, Kenneth and Isabel

Rain falls and soaks into the soil, picking up nitrate and other minerals as it drains into tiles, which are underground, perforated pipes that carry excess water away from farmland. This empties into a drainage ditch where it converges with water from many other pipes and flows downstream to the Raccoon River, which eventually flows past the city of Des Moines.


A legal organization of landowners in a watershed that build and maintain ditches and tiling to provide a path to drain excess water from a watershed.

“A drainage district is like a leaf. If the entire leaf is a watershed, the veins are the pipes and ditches in the district. The veins start small, as the tiles under individual farms. These tiles feed the farm drainage into bigger pipes and ditches. The water then flows into a river, the stem of the leaf, carrying all of the nutrients collected from the farmland to that point. Without the pipe system to carry excess water off the fields, farming in Iowa would be impossible.”

Field Specialist
Iowa State University
Iowa Falls, IA

Water from all the sanitary drains and sewers in the cities of Ames and Kelly is filtered through the Ames Water Pollution Control Facility.

by Michael, Alex, Kenneth and Isabel

If water is used inside a home or structure it comes there to be treated. Once in the facility, water goes through biological and physical processes that remove solids, reduce the level of ammonia, and kill microorganisms. Water discharged from the facility is released from this pipe into the South Skunk River.


A source of pollution that discharges from a specific, confined site.

National Pollutant Discharge Elimination System (NPDES)

A provision of the Clean Water Act that regulates point sources that discharge pollutants into US waters.

Point sources of pollution are regulated by the National Pollutant Discharge Elimination System (NPDES) to allow discharge of treated materials, such as wastewater. Point sources include municipal, industrial, and commercial sites. Non-point sources are not regulated by the NPDES and include farm tiles, fields, storm sewers, and drainage ditches.”

City of Ames Water Pollution Control Authority
Ames, IA

IF WE DIDN’T HAVE the Haber-Bosch process, 3 billion people would be without food, claimS professor john sawyer of iowa state univeRsity. It’s the chemical reaction that feeds the world.

John Sawyer specializes in soil fertility and nutrient management at ISU, where he works with producers and crop advisors in researching the best management methods of nitrogen fertilizer. Co-ops like like Key Cooperative in Story City, Iowa are prevalent in the Midwest; they make it simpler for large amounts of nitrogen fertilizer to be applied across the nation. Fertilizer accounts for 80% of the ammonia produced in the US, with the rest used in household cleaners and other nitrogen compounds, like nitric acid.

“An advantage of using ammonia fertilizer is a yield increase corn and other crops. A disadvantage of the application is higher amounts of excess nitrogen in the soil that is added to the local water system.”

Professor in Agronomy
Iowa State University
Ames, IA


An industrial method that produces ammonia from bonding nitrogen and hydrogen with an iron catalyst under high pressure and heat.

“It’s a complicated issue,” GREG SAYS. “I don’t like the way the media paints farmers. We’re not the bastards we’re made out to be.”

by Frank and Molly

“Plants need nitrogen to grow and they get that nitrogen by absorbing either nitrate or ammonium through their roots. With a corn-soybean rotation, like most Iowa farms, some of that nitrate has to come from fertilizer. Here, we’re very exact with our application and, generally speaking, the amount farmers apply has been going down each year.

“Corn takes a pound of nitrogen per bushel, and on a good year we get 250 bushels per acre. About 20-30 pounds of nitrate comes from decaying plant matter. The remaining amount is mostly covered by the 4000 pounds of liquid manure once the ground is steadily below 50°F, with extra ammonia added in the spring.

“We don’t want to spend any more on fertilizer than we have to. We know the timing and movement in the soil profile affects leaching more than the amount of nitrate put on the fields. As a result we’re considerate of things like when waves of rain are coming in because nitrate is water soluble; where the water goes so too does nitrate. We keep three feet of ground between where we inject the manure and where our tile line is. Overall, as technology becomes available it will get utilized. We’ll get better.”


A molecule that consists of one nitrogen atom and three oxygen atoms.


A soluble mineral or chemical that drains away from soil by the action of a percolating liquid, especially rainwater.


by Alec, Jake and Maxwell

In fields where the water table is close to the surface, tile drainage is used to remove excess water from the soil. This contributes significantly to nitrate (N) contamination of Iowa surface waters and ultimately the Mississippi River.

At Iowa State University, scientists use sump pits to collect water samples from three fields using different farming practices. Then they calculates the concentration and volume of nitrate in this subsurface drainage water. Nitrate testing in these fields shows that organic farming leaches less nitrogen than more conventional methods.


The downward movement of nitrate through the soil. Nitrogen is a main component in fertilizer, and nitrogen leaching occurs when excess fertilizer is placed on crops.


The excessive enrichment of a waterway (lake, river or ocean) by dissolved nutrients (such as phosphates) that stimulate the growth of aquatic plant life, usually resulting in harmful algal blooms (HAB) that deplete dissolved oxygen and lead to rapid fish die offs and loss of safe drinking water.