How Does Tile Drainage Work? Crop Benefits and Environmental Impacts

Tile drainage is a system of pipes installed below ground to remove excess water from farmland soil. Just as irrigation is often necessary to deliver water to soil and crops, drainage is important in many agricultural systems to prevent the soil from becoming oversaturated with water, which can damage crops and farm machinery.

This network of pipes placed at varying depths helps farmers maintain a consistent level of soil moisture, increase crop productivity, and avoid losses from extreme weather. However, tile drainage may carry pollutants into streams and groundwater as well as change the hydrology of watersheds. It can also be detrimental to wetland habitat and interfere with the natural flood control that wetlands provide.

History and Evolution of Tile Drainage

Various types of subsurface drainage systems have been employed in the United States during the past two centuries. Vast areas, including many parts of the Midwest, Southeast, and Gulf Coast, were originally wetlands. As the country grew and more land was converted by settlers for farming, subterranean drainage systems became common. 

Originally, farmers installed clay piping—and later, concrete pipes—to remove excess water. In the early 20th century, federal and local governments began creating drainage districts to manage these efforts. Accompanying innovations in drainage technology further advanced the practice.

Today, however, wetlands are protected as important habitats for wildlife and because they provide ecosystem services like flood control and water quality. This means tile drainage systems must adhere to regulations in order to avoid wetland damage.

Installation

Most drainage pipes are no longer made from clay piping but from polyethylene tubing; the word “tile” or “tiling” is a holdover from the materials and design previously employed. The artificial pipes are placed at a slope just below the crop root area. Through perforations in the pipe, excess water enters and can then be directed into a ditch or other means of conveying water away from the field. 

Farmers who install subsurface drainage systems must understand the land’s soil characteristics. They must also make calculations about the best size of pipe to use and the optimal slope at which to place the pipe for effective drainage. Accurate assessments ensure that sediment won’t build up and cause pressure problems at vulnerable pipe joints or compromise the pipes in other ways. It’s also important to design the system so that the underground pipes have correct spacing and depth for the soil and precipitation conditions; this ensures uniform, effective drainage. 

An experienced installer will dig trenches in which to place and connect the pipes carefully so that the system avoids damage and erosion over time. An installer must also take care to follow state and local regulations pertaining to the local watershed and wetlands.

A tile drainage system also requires periodic inspection and maintenance to minimize environmental impacts and ensure the system’s longevity, and the farmer must ensure that the soil is managed properly over the long term to prevent damaging the subterranean pipes.

Crop Benefits

Once installed, a crop drainage system provides a variety of potential benefits for farmlands. These include effective soil aeration, less plant stress, greater crop productivity, more flexibility with planting time and crop varieties, more efficient harvesting, and less wear and tear on farm machinery.

Tile drainage helps crops adapt to changing climatic conditions, including extreme rainfall that leads to flooding. Well-drained fields tend to experience less erosion. In some areas, farmers with drainage systems may be able to implement additional conservation practices like cover crops because they can access fields earlier and later in the season. In addition, drainage may save on labor costs associated with working wet fields, which make for more challenging soil conditions.

Environmental Impacts

Tile drainage systems also have significant environmental impacts, in part because water drained from agricultural land often contains pesticides and fertilizers like nitrogen and phosphorus, which can end up in rivers, streams, wetlands, and groundwater, impairing water quality.

Additionally, excess nutrients like nitrogen and phosphorus in fertilizer have been shown to cause algal blooms capable of producing toxins that harm people, fish, and other wildlife, as well as impact fishing and recreational activities on water. Large algal blooms reduce oxygen levels in water, called hypoxia, which leads to dead zones when aquatic species like fish, coral, and seagrass cannot survive the low-oxygen conditions. Agricultural runoff is the biggest culprit in nutrient pollution, and tile drainage is a significant contributor to that runoff as it directs nutrients into waterways that then flow into bays, lakes, and coastal waters from upstream farms.

The Great Lakes and the Chesapeake Bay have both been plagued by serious nutrient pollution and algal blooms in recent years. According to the Environmental Protection Agency, the largest dead zone in the United States is in the Gulf of Mexico, where masses of aquatic organisms die each year because of nutrient pollution coming from the Mississippi River Basin.

Tile drainage can also affect hydrology in a watershed by changing streamflows and increasing erosion, which has the potential to alter a stream’s course and lead to flooding and wetland damage. These changes can affect the habitats of aquatic species, and flooding may also end up impacting other farmlands along rivers and streams. 

Interestingly, climate change is leading to increased use of tile drainage in some regions. For example, many Midwest farmers whose crops are inundated by extreme rainfall events have opted to install tile drainage systems to cope with such changing, unpredictable weather conditions. In Illinois, over 10 million acres have been tiled, amounting to 35% of its croplands. In Indiana and Ohio, a whopping 50% of croplands are tiled.

Given the potential for environmental damage, it is becoming all the more important to understand and regulate the use of tile drainage systems across a watershed, including identifying areas where tile drainage would lead to serious environmental impacts.    

Can Tile Drainage Work for Gardens and Small Farms?

Today, tile drainage is popular not just on large farms, but among small farmers and even homeowners seeking to avoid waterlogged yards and backyard gardens. Tile drainage systems are promoted by landscapers and can be purchased at home improvement stores.

However, amateurs beware: There is good reason to proceed cautiously with the decision to invest in tile drainage—or any kind of drainage—for a backyard garden or even a small farm. The internet is full of how-to videos about installing these systems yourself. Don’t be seduced into thinking that anyone with DIY savvy alone is equipped to build a successful drainage system. 

It’s important to first know all laws and regulations regarding the installation and maintenance of these systems in order to assess whether it’s feasible and legal to do so. And just as for larger farms, finding a qualified installer is necessary to ensure such a system doesn’t cause legal or financial headaches—or lead to unintended environmental damage. Once the unknowns, including costs, regulations, and land conditions, are thoroughly explored, you're ready to make a feasibility assessment.