Picture transitioning from a rural setting that includes woodlands, wildlife habitat and farms, to urban areas that consist of concrete, parking lots, streets and buildings. Rural land in a more natural state has the ability to soak up water in the soil more efficiently than urban areas with impervious surfaces that can lead to more runoff.
“Soil has a wonderful filtering capacity,” said Stacy Hutchinson, professor of biological and agricultural engineering at Kansas State University. “As water moves through the soil, pollutants such as heavy metals and excess nutrients bind to the soil’s surface and are removed from the water.”
Many of the pollutants that soil filters out of water are resources that can be used in other environments, Hutchinson said. For example, plants and microorganisms can use excess nutrients filtered out of the water and into the soil as a food source.
“The pollutants themselves tend to be similar between the rural and urban landscape, but what we see in the urban landscape is an increased amount of runoff that can generate more soil erosion,” she said. “Urban stream channels tend to be highly degraded due to excess water in the channel flowing at a much quicker pace.”
Studying landscapes in rural and urban areas is necessary to determine how soil and water—two required resources to sustain life—work together. Scientists know that soils serve as a natural remedy to purify water, and educating the public about this ties into the April theme for the 2015 International Year of Soils, “Soils Clean and Capture Water.”
Soils benefit all areas
Hutchinson currently serves as interim director for K-State’s Urban Water Institute, which was formed in 2011 to examine water issues in urban and urbanizing areas. She said because of changes to the landscape and the population density of urban areas, people here tend to manage water a bit differently.
“The Urban Water Institute was founded on the concepts of innovation, education and collaboration,” Hutchinson said. “We research handling water in the urban environment and educate small children to our campus students. We have 60 faculty across our K-State campuses that collaborate with K-State Research and Extension to get this information out further across the state to protect our water system.”
A majority of the education surrounds understanding the development of economies based on the availability of water, she said, in addition to appreciating various treatment technologies for drinking water, storm water and wastewater.
DeAnn Presley, a K-State Research and Extension soil scientist, works with local health departments across Kansas in wastewater management. She said most Kansans are on municipal wastewater treatment systems, where a home’s sewer pipe connects to a sewer main on the street. But, individual wastewater treatment systems such as septic systems or lagoons are in place for an estimated 200,000 to 250,000 homes in Kansas.
“Soils are a critical part of on-site wastewater treatment systems,” Presley said. “The systems are all designed and sized based on soil characteristics.”
The main characteristics include the composition of the soil, or how much sand, silt and clay are available, as well as the structure of the soil.
“If the soil is well-structured, it can accept water,” Presley said. “For heavier textured soils, soils that have more clay, either a lagoon or alternative evaporation-based or drip system will be designed.”
“Lots of new subdivisions, for example, aren’t on a municipal wastewater treatment system,” she added. “It costs millions of dollars to create those municipal systems. Under-sizing an onsite wastewater treatment system, or putting the wrong system in that eventually fails, is costly to a homeowner.”
On the rural side, Presley also works with farmers to improve the soil’s ability to capture water. One way is using cover crops, which are grown between cash crops such as wheat, corn, sorghum or soybeans.
Cover crops are destroyed at or before the cash crops are planted. Cover crops might include legumes such as alfalfa, red clover or cowpeas that tend to fix nitrogen composition in the soil. Others might include various grasses or vegetables such as turnips.
“Kansas can be a hot, dry place,” Presley said. “(Cover crops) shade the soil surface during our long summers, can reduce evaporation and keep moisture at the ground for cash crops.”
Another advantage of cover crops is they provide more organic matter for the soil, which helps improve soil quality, and they often attract wildlife and beneficial insects.
“Farmers have to consider how much they can spend on cover crop seeds and which seeds to buy,” Presley said. “Cover crops can be hard for farmers to monetize, but for citizens of Kansas and the Great Plains in general, they are definitely a win. Cover crops used for grazing cattle have been economically favorable. Many farmers also take environmental stewardship seriously and have a lot of pride in it.”
To watch a video interview with Hutchinson and Presley, log on to the K-State Research and Extension YouTube page (https://www.youtube.com/watch?v=ExB0W85Zo1w&feature=youtu.be&list=PLAD45744D5128C8EB). The Soil Science Society of America has numerous resources for the public, teachers and children about soil and each monthly theme for the International Year of Soils. Log on to www.soils.org.