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K-State Research and Extension News

Researchers eye cover crops, fertilizer to boost water quality

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Released: Dec. 18, 2015

MANHATTAN, Kan. – Steady rains that peppered much of Kansas in early December may have caused inconveniences for travelers and shoppers, but they were a blessing of sorts for Nathan Nelson.

Nelson, an associate professor of agronomy at Kansas State University, oversees the Kansas Agricultural Watershed field laboratory, an expansive project south of Manhattan to measure the effects of agricultural production systems on surface water.

The approximately 30 acres of research land is dissected into 18 field plots, each about the size of a football field. Researchers are learning more about what happens to phosphorus and nitrogen – two nutrients common to agricultural crop fertilizers – when rainwater snakes it way to local streams and rivers.

“A lot of phosphorus use in Kansas is in agriculture,” Nelson said. “We are looking at ways to continue using that phosphorus to grow crops, maintain our agricultural and economic competitiveness, but minimize potential impact of those nutrients on water quality.”

Kansas’ reservoirs have recently felt the pain of poor water quality, many due to chronic algal blooms. Over the last 15 years, city and state officials have increasingly been forced to close public waterways to recreation and fishing due to health concerns.

Nelson noted that poor water quality also affects nearby land values, and when cities pay more to clean up that water, it ultimately means a bump in the homeowner’s water bill. All of these issues affect the local economy.

“We want to be able to reduce those algal blooms,” Nelson said. “It’s important to realize that we put nutrients like nitrogen and phosphorus on our crop fields because plants need them to grow. The same thing happens when you put them in the water; the algae, like a plant, responds to these nutrients, and they grow more. You can reduce the growth if you reduce the inputs.”

The project that Nelson leads aims to do just that, so long as Mother Nature cooperates with rainfall that allows his research team to replicate field conditions. Currently, his team is testing corn and soybean fields in which fertilizer was applied in spring, fall or not at all; and with or without a cover crop planted after the main crop.

Cover crops are often planted as a winter crop to manage soil erosion and improve soil fertility. They may also help decrease weeds, pests and diseases in the field.

“The land we’re using is small enough to manage it from an experimental standpoint, but large enough so that all of the natural processes that are occurring in a producer’s field are occurring in these plots,” Nelson said.

Just in its first year, the project’s results are promising, he said.

“We did see that cover crops significantly reduced phosphorus and sediment loss in runoff,” Nelson said, adding that cover crops cut those losses by more than 50 percent.

The early research also leaned favorably toward the value of cover crops as a best management practice to reduce phosphorus loss from broadcast-applied fertilizer.

“Although fall broadcast fertilizer increased soluble phosphorus loss compared to fertilizer injected in the spring, the use of cover crops cut that loss by 60 percent,” Nelson said.

Even so, data is sparse, and Nelson continues collecting data to determine long-term impacts of these practices. The research team also is working to determine the effects of tillage systems and rainfall events at different times of year, and how these findings vary across the state.

“There are a lot of questions related to the effects of agricultural systems on water quality,” he said. “In order to evaluate and improve our agricultural practices and models, we need more data. Eventually, we hope to make recommendations on best management practices and where those might fit. It looks promising after one year.”


K‑State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well‑being of Kansans.  Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K‑State campus in Manhattan.

Story by:
Pat Melgares
K-State Research and Extension

For more information:
Nathan Nelson – 785-532-5115 or nonelson@k-state.edu