By upgrading field drainage and incorporating conservation structures, such as wetlands, bioreactors and saturated buffers, farmers in Iowa and other parts of the Corn Belt have an opportunity to both increase crop yields and significantly improve water quality, according to new study led by Iowa State University (ISU) agronomists.

“If we upgrade drainage the right way and incorporate water quality, it really can be a win-win situation that benefits both the farmers and the environment,” said Michael Castellano, an ISU professor of agronomy and lead author of the study.

The study was done by ISU agronomists in cooperation with researchers from the University of Kentucky and Swiss Federal Institute of Technology ETH-Zurich and was published recently in the academic journal Nature Sustainability.

The researchers, who based their finding both on field experiments and computer simulations, found that much of the field drainage installed in Iowa and around the Corn Belt about a century ago is deteriorating, obsolete or in dire need of an upgrade.

Changing conditions

Old drainage systems have become inadequate because the Corn Belt, overall, is getting wetter and rain events of several inches at a time are far more frequent, Castellano said. Farmers also farm differently today than they did when the older drainage was first installed, he said. In the early 20th century, Corn Belt farmers planted more fields to forage crops that are not as dependent on drainage, the ISU agronomy professor noted.

Improving drainage systems would both increase yields and create more resilient production systems, the study’s authors said. Better drainage would also reduce delays in planting, harvesting and other field work because fields would dry faster and would support machinery, they said.

“We know that we need to upgrade these drainage systems and increase the capacity of the field tile and the mains to handle a larger volume of water,” Castellano said. “So, while we do that, we need to add edge of field water quality practices, such as wetlands, bioreactors and saturated buffers.”

The water quality structures, Castellano said, can positioned to take little to no land out of production. The structures, and especially wetlands, would also add diversity to the landscape and could even offer landowners opportunities to earn money selling or leasing land for hunting or other outdoor activities, he said.

Boosting water quality

At the same time, Castellano said, the added conservation structures could give a big boost to the continuing efforts of farmers in Iowa and other states to improve water quality and wildlife habitat.

Strategic planning is necessary to successfully upgrade drainage while improving water quality, the ISU agronomist said. It will be important to take a watershed approach, and install wetlands and other structures where they can do the most good in a watershed, he said.

“Each watershed is different and will need different structures,” Castellano said. “We will have to look at one drainage district at a time.”

A big investment

The researchers admit that upgrading draining would require a big investment and would also likely require approval from the U.S. Department of Agriculture’s Natural Resources Conservation Services to remain in compliance with wetland conservation requirements or other federal agencies to assure there are no Clean Water Act wetland violations.

In addition, it’s sometimes difficult to get a consensus among all landowners in a drainage district to make the investment in mains and other infrastructure at a time of low commodity prices, they said.

But, as Castellano said, “we have this enormous infrastructure investment that’s deteriorating. If we update it the right way, we can benefit crop production and the environment. If we don’t, it will be extremely difficult to meet agriculture’s water quality goals and retain our crop production potential.”