Agricultural Tile Drainage in the US Corn Belt: Past, Present, and Future

by Rwit Chakravorty, Hongli Feng, David A. Hennessy, and Michael J. Castellano

Vast networks of drains, pipes, and tiles that support food production on some of the world’s most fertile farmland, such as the US Corn Belt, are in need of expansion and renewal amidst the growing challenges posed by climate change.

What is tile drainage?

Agricultural subsurface drainage systems, or tile drainage, consists of networks of perforated pipes installed beneath croplands to remove excess water. The primary benefits of drainage systems are twofold: (a) they protect soil and crop health; and, (b) they enable earlier planting (Pavelis 1987). By alleviating waterlogging and enhancing soil aeration, subsurface drainage systems promote stronger root growth and improve nutrient uptake (Castellano et al. 2019), leading to increased crop yields, increased nitrogen use efficiency, and reduced nitrous oxide emissions. Another key advantage of drainage is in allowing for timely field operations, such as planting, which is a strong predictor of yield. This principle has long been recognized, where Cato in De Agricultura (200 BCE) advises: "See that you carry out all farm operations betimes, for this is the way with farming: if you are late in doing one thing you will be late in doing everything."

Figure 1 shows the county-level extent of tile drainage as a fraction of cropland in the Midwestern US according to the 2017 US Census of Agriculture.

Figure 2 is a Lorenz curve visualization of the relationship between crop production and the share of county cropland tiled. The curve's convexity and position below the 45-degree line indicate that a disproportionate share of agricultural production (y-axis) comes from counties with higher drainage intensity (x-axis). As we move from counties with little or no drainage to those with higher levels of tiling the cumulative share of production increases rapidly, suggesting that heavily drained counties contribute significantly more to total crop output than do their less drained counterparts, which highlights the importance of tiling in driving agricultural productivity at the county level.

Tile drainage in the context of climate change in the United States

The US Midwest is grappling with growing challenges linked to climate variability. Studies show that the region is experiencing shifting precipitation patterns, including wetter winters, drier summers, and more frequent intense rainfall events (Bowling et al. 2018). Projections from the US Global Climate Change Research Program suggest that climate change will lead to a further increase in intense rainfall events throughout the year, along with prolonged summer droughts during the growing season. Excess precipitation can lead to significant crop losses. Most field crops can endure heavy rainfall without suffering long-term damage as long as the water table drops to six inches below the surface within a day and continues to fall to 18 inches within three days (Hofstrand 2016). This underscores the importance of swiftly draining excess water from fields to maintain the reliability of food production. Meyer and Keiser (2016) argue that tile drainage is an adaptation tool in regions prone to extreme precipitation, especially in poorly drained areas. Drained croplands, while comprising a small portion of total US farmland, contribute disproportionately to food and feed production. While every state has some drained cropland, more than 50% of cropland acres in the northern Corn Belt are drained. However, states installed much of this infrastructure over a century ago, for a different agricultural era, when pastures and forage crops, which require less drainage than today's grain crops, were more prevalent. These drainage networks need improvement to adapt to modern crop production.

Policy background

Tile drainage in the United States began in the nineteenth century, driven by federal policies like the Swamp Land Acts (1849, 1850, 1860), which transferred wetlands to states for development. At the time, states viewed wetlands as obstacles to land development, often seen as breeding grounds for mosquitoes. The primary objective of the act was to allow states to reclaim these areas by constructing levees, ditches, and drainage systems to make the land more usable. However, inadequate funding led to a shift in responsibility from states to counties and ultimately to private landowners. For landowners, the decision to invest in tile drainage is complex due to coordination challenges (Edwards and Thurman 2022). Drainage systems consist of networks of pipes on individual farms that feed into a shared, community-managed main drain. The effectiveness of this setup depends on both the on-farm infrastructure and the main drain working together to remove excess water. Main drain maintenance and operation rely on collective action, requiring coordination between individual farmers and the community's drainage districts, which can introduce potential sources of friction.

To address coordination challenges in drainage projects, some states established drainage districts—special districts with local taxing authority and the power of eminent domain to facilitate collective investments. In Iowa, for example, following passage of drainage district legislation in 1884 (Sherman 1924) much of Northern Iowa was drained. In Story County, Iowa, drainage districts covered 197,633 acres (58% of all land) by 1920, financing improvements through land taxes (Hewes and Frandson 1952). From a modern governance perspective, drainage districts are a form of special district established with local authority parallel to county and municipal governments but subordinate to state governments. Drainage districts were typically formed through landowner petitions and governed by elected boards, which coordinated drainage investments for public benefit (Prince 2008). Although drainage districts provide legal structure to support coordinated drainage investments, disputes are common as vertical location within the watershed, land quality, tenancy issues, and intended land use create heterogeneous incentives to pay among participants.

Negative externalities and their solutions

Most of the early artificial drainage infrastructure, while beneficial for agricultural productivity, came with significant environmental drawbacks, primarily through depleting wetland and moving nutrients from fields to nearby water systems without benefit of natural filtration processes. For instance, research in northeast Iowa demonstrates that tile drainage was responsible for over 50% of the nitrogen load in watersheds during the growing season (Arenas Amado et al. 2017). Elevated nutrient levels in water bodies contribute to increased phytoplankton growth, which can lead to hypoxic or "dead zones" with low oxygen levels, negatively impacting aquatic ecosystems.

Technological advances aim to mitigate these environmental impacts. Controlled drainage (CD) controls the volume of water leaving the field by using adjustable structures (e.g., weirs or gates) installed in a drainage system outlet. Wang et al. (2020), show CD can increase yields while reducing both outflow and nutrient loss when compared to conventional drainage systems. Denitrification wetlands are an edge-of-field technology that reduces nitrate runoff by naturally filtering drainage water before it enters larger bodies of water. Edge-of-field nutrient-loss reduction practices, which are only applicable to drained acres, are among the most cost-effective methods in terms of dollars per pound of nutrient loss reduced, as well as in terms of percentage reduction in nutrient loss per acre. The Conservation Drainage Network (see https://conservationdrainage.net/), a nationwide collaboration to promote drainage practices that strike a balance between reducing negative environmental impacts and sustaining future crop production, provides resources on how to implement long-term conservation practices, such as denitrification wetlands, bioreactors and saturated buffers.

Farmers and communities face a growing need to modernize and expand drainage systems to protect productivity under climate change. Recent drainage technology developments emphasize both profitability and environmental conservation. These innovative drainage technologies may become increasingly important to agriculture in the upper Midwestern US.

Barriers to adoption and potential solutions

The high upfront costs of installing both drainage systems and accompanying innovations like wetland structures can act as a barrier to widespread adoption. In order to delve deeper into farmers’ tile drainage adoption behavior, we conducted a farmer survey between March and May 2024 across 870 counties in the US Corn Belt. The study area spanned 12 Midwestern states, focusing on heavily tile-drained regions and neighboring counties with potential for drainage expansion. Out of a sample of 3,000 farm operators, we received a response rate of 20% with 520 usable responses for analysis. Figure 3 depicts respondents’ perceived barriers to tile drainage investments. Payback period is reported as the most important factor, indicating that the majority of respondents consider financial impacts, as embodied by the length of time needed to recoup the upfront costs, to be the most significant barrier.

Green bonds, a type of fixed-income security issued to finance projects that have positive environmental or climate benefits, could bridge this gap by providing financing for drainage upgrades that integrate denitrification wetlands. The environmental benefits generated from such projects, such as reduced nitrate levels in runoff, align well with the goals of green bonds, which are often designed to support measurable environmental outcomes. Green bonds could be designed with performance-based incentives—for instance, if the reduction of nitrates in water runoff surpasses a predetermined threshold, the bond issuer (likely a government or cooperative) would pay a lower coupon rate. This creates a financial incentive for all stakeholders, including farmers, investors, and environmental agencies, to prioritize effective water management practices. See https://enviroaccounting.com/green-bonds-and-pay-for-performance/ for more details about green bonds.

Figure 4 offers another key insight—21% of respondents feel that specifications in the rental contract are a significant barrier to investment. This can also relate to concerns regarding payback period. The impact of land tenure on adopting tile drainage depends on the distribution of costs and returns. For non-farming landowners, one strategy is to make the tiling investment and then recover the costs by charging tenants a higher cash rental rate. In contrast, tenants who make the tile drainage investment typically receive the additional net returns without an increase in rent since the landowner incurs no upfront costs. However, a tenant’s major concern is whether they will have access to the land long enough to justify this capital expenditure. Approximately half of the farmland in the Midwest is rented under short-term leases, which can discourage tenants from investing in practices that offer long-term returns. This issue is becoming increasingly prevalent—in 2017, only 37% of farmland in Iowa was owner-operated, a 13 percentage-point decrease since 1982 (Zhang, Plastina, and Sawadgo 2018). One solution is to maintain the standard one-year lease while establishing a separate contract that specifically addresses tile drainage investments. Under this agreement, the tenant would receive a pro-rata buyout from the landowner for their tiling investment if they stop renting the farm before the end of the tile’s useful life (Hofstrand 2016). Thus, rental contract terms, including lease length and payment arrangements, are critical in shaping incentives for tile drainage investment.

Our survey also finds that the majority of respondents are unfamiliar with conservation drainage infrastructures like CD and wetlands. This knowledge gap suggests opportunities for problem mitigation. The policy implications are clear—there is a need for more education and outreach to farmers and landowners about these innovative drainage solutions, ensuring they have the knowledge and resources to assess and possibly implement them effectively.

US agriculture's reliance on drainage has expanded from an early focus on productivity to a modern understanding that also includes its environmental implications. Despite the vital role of subsurface drainage in making much of the Midwest’s land arable, our survey reveals persistent barriers to wider adoption of modern drainage systems. Key challenges include rental contract terms that discourage long-term investments and a lack of awareness about conservation drainage practices. Addressing these issues may require policy interventions that promote innovative rental agreements, and increased education and outreach. Such efforts will help in enhancing drainage adoption, mitigating environmental impacts, and supporting agricultural resilience in the face of climate change.

References

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Edwards, E.C., and W.N. Thurman 2022. "Creating American Farmland: Governance Institutions and Investment in Agricultural Drainage." Working paper 30081. National Bureau of Economic Research.
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Prince, H. 2008. Wetlands of the American Midwest. University of Chicago Press.
Sherman, J.J. 1924. Drainage Districts in Iowa: A Study in Local Administration. University of Iowa.
Wang, Z., G. Shao, J. Lu, K. Zhang, Y. Gao, and J. Ding. 2020. "Effects of Controlled Drainage on Crop Yield, Drainage Water Quantity and Quality: A Meta-analysis." Agricultural Water Management 239:106253. https://doi.org/10.1016/j.agwat.2020.106253.
Zhang, W., A. Plastina, and W. Sawadgo. 2018. "Iowa Farmland Ownership and Tenure Survey 1982-2017: A Thirty-five Year Perspective." PM 1983. Iowa State University Extension and Outreach, Iowa State University. https://store.extension.iastate.edu/product/6492.

Suggested citation

Chakravorty, R., H. Feng, D.A. Hennessy, and M.J. Castellano. 2024. "Agricultural Tile Drainage in the US Corn Belt: Past, Present, and Future." Agricultural Policy Review, Fall 2024. Center for Agricultural and Rural Development, Iowa State University. https://agpolicyreview.card.iastate.edu/fall-2024/agricultural-tile-drainage-us-corn-belt-past-present-future.