Massive networks of drains, pipes and tile lines that enable food production on much of the world’s most productive cropland are due for expansion and replacement to meet the demands of agricultural intensification and climate change. How that infrastructure is updated will have enormous consequences on food production and the environment, according to a new study.

The study outlines the need for an overhaul of ag drainage infrastructure. Such an update would require major investment and widespread consensus from policymakers, taxpayers and producers, says Mike Castellano, an Iowa State University agronomy professor and lead author of the study.

But the effort would be a sound long-term plan with a range of benefits, he adds. ISU agronomists collaborated with scientists at the University of Kentucky and the Swiss Federal Institute of Technology on the study. The researchers based their findings on field experiments and computer simulations.

“We have this enormous infrastructure investment that’s deteriorating and needs to be updated,” Castellano says. “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.”

Aging infrastructure

Cropland has been drained for millennia, but technology invented in the mid-1800s enabled widespread installation of drainage systems, which rapidly spread from Europe to North America. Miles of strategically placed tiles and pipes allow water to flow away from farm fields, which keeps soils dry enough for farmers to cultivate crops. Without that drainage, many temperate humid croplands, such as the northern U.S. Corn Belt, would be too swampy to farm.

But much of the drainage infrastructure has outlived its design life and was built for a different era in agriculture, when pastures and forage crops that require less drainage than grain crops were more commonly grown. Climate change has increased precipitation, further taxing the aging drainage infrastructure, Castellano says.

An overhaul of ag drainage would require the installation of higher-capacity pipes, as well as implementing long-term conservation practices, such as denitrification wetlands, bioreactors and saturated buffers. For instance, converting between 1% and 6% of Iowa farmland to wetlands can reduce nitrate loads by 25% to 78%. 

Forging the consensus and raising the tax dollars for such a major undertaking would pose a serious challenge. In Iowa alone, there are 3,700 drainage districts, and they make independent infrastructure maintenance decisions. Much of Iowa’s drainage infrastructure was built during the 1920s or earlier. 

Benefits of updating

The study reports that a range of benefits would result from an update to drainage infrastructure. For instance, implementing conservation practices near the ends of drainage pipes would reduce the runoff of nitrogen fertilizer. That would improve water quality and reduce the amount of nitrogen that flows downstream and contributes to hypoxic zones, such as in the Gulf of Mexico.

Better drainage also would cut down on agricultural greenhouse gas emissions by reducing the optimal amount of fertilizers used by farmers. Dryer soils also release less nitrous oxide, a greenhouse gas. 

“Overall, drainage increases crop yield and nitrogen fertilizer use efficiency — a win-win for the farmer and the environment,” says Sotirios Archontoulis, an ISU agronomy professor and co-author of the study.

Drainage systems built to address modern realities would allow for better yields and more resilient production systems. The study notes that wet and poorly drained fields experience more disease and suboptimal root growth. Wet fields also make it difficult for farmers to get machinery into their fields to plant, harvest and take care of their crops. 

“Delayed planting has a direct negative effect on yield potential due to a reduction in growing degree days,” Archontoulis says. “Higher-capacity drainage may have helped farmers in spring 2019 when rainy weather kept farmers out of fields for weeks.” 

The study is available online. 

Drainage faces a fork in the road

About two-thirds of Iowa’s crop acres benefit from field drainage. “Without it, we wouldn’t be producing the crops we are today,” says ISU agronomist Mike Castellano. “On the other hand, field drainage is contributing to the water quality challenges we have in Iowa. Many of the drainage systems were installed by our grandfathers and great grandfathers, and need to be updated. If we do it the right way, we can benefit both our state’s crop production and the environment.”

Each farmer is responsible for maintaining the tile lines in their fields. But the large drainage pipes and ditches at the ends of fields that carry water to streams and rivers are a community resource managed by drainage districts. The districts are made up of groups of farmers and landowners.

“There is real opportunity to make these drainage district systems bigger, to install larger drainage pipes and higher-capacity systems,” Castellano says. “It’s something that needs to be done in the face of climate change where we are receiving more and heavier volume rain events.”

Spring 2019 was one of the most difficult Iowa has ever had dealing with rain delays and late planting. “Improved drainage would be one way to avoid or certainly minimize these challenges in the future,” he says. “It’s not just making the drainage pipes bigger, but also coupling that with installing conservation practices such as denitrification wetlands, bioreactors and saturated buffers.”

Iowa has 3,700 drainage districts, all operating independently. It can be a challenge to get everyone in a drainage district to agree that an upgrade is necessary and worth the amount of money it takes to make an upgrade in the district’s system to drain water away. Each farmer in the district pays taxes so the district can maintain and upgrade its system. The Iowa Drainage District Association has information at iowadrainage.org.

The districts provide a legally organized way to construct and maintain adequate drainage outlets and levees. Land within an established drainage district can be assessed for construction, maintenance and repair of drainage district facilities. Assessments are based on relative benefits received and may be spread over several years. The process of determining the relative amount each landowner pays when an assessment is made is called classification.

Source: ISU, which is responsible for information provided and is owned by source. Informa Business Media and subsidiaries aren’t responsible for content in this information asset.