Soil and water

How does tile drainage work? Benefits for crops and environmental impacts

Underground drainage is a system of pipes installed underground to remove excess soil water from agricultural land. Just as irrigation is often required to provide water to soil and crops, drainage is important in many farming systems to prevent the soil from becoming supersaturated with water, which can damage crops and farm machinery.

This network of pipes placed at different depths helps farmers maintain a constant level of soil moisture, increase crop productivity and prevent losses from extreme weather conditions. However, subsurface drainage can transport pollutants into streams and groundwater and alter 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 underground drainage

Various types of underground drainage systems have been used in the United States over the past two centuries. Large 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 agriculture, underground drainage systems became common.

Originally, farmers installed clay pipes, and later concrete pipes, to remove excess water. At the start of the 20th century, federal and local governments began to create drainage districts to manage these efforts. Associated innovations in drainage technology have further advanced the practice.

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


A drainage pipe releases water from a paddy field.

Nugroho Ridho / Getty Images

Most drainage pipes are no longer made from terracotta pipes but from polyethylene pipes; the word “tiling” or “tiling” is a holdover from the materials and design previously employed. The artificial pipes are placed on a slope just below the root zone of the crop. Through the perforations in the pipe, excess water enters and can then be directed to a ditch or other means of draining water from the field.

Farmers who install underground drainage systems need to understand the soil characteristics of the land. They also need to make calculations on the best size of pipe to use and the optimum slope on which to place the pipe for effective drainage. Accurate assessments ensure that sediment will not build up and cause pressure issues at vulnerable pipe joints or otherwise compromise pipes. It is also important to design the system so that the underground pipes have the correct spacing and depth for the soil and precipitation conditions; this guarantees uniform and efficient drainage.

An experienced installer will dig trenches in which to place and connect the pipes with care so that the system prevents damage and erosion over time. An installer should also be sure to follow national and local regulations relating to the local watershed and wetlands.

A subsurface drainage system also requires periodic inspection and maintenance to minimize environmental impacts and ensure the longevity of the system, and the farmer must ensure that the soil is properly managed over the long term to avoid damaging the pipes. underground.

Benefits of crops

Once installed, a crop drainage system offers a variety of potential benefits to farmland. These include efficient soil aeration, less plant stress and disease, greater crop productivity, more flexibility with planting time and crop varieties, more efficient harvesting and less wear and tear on the crops. agricultural machinery.

Subsurface drainage helps crops adapt to changing climatic conditions, including extreme precipitation 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. Additionally, drainage can save labor costs associated with working wet fields, making soil conditions more difficult.

Environmental impacts

Algae blooms occur after agricultural runoff enters a stream.

David Pardoe / Getty Images

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

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

The Great Lakes and Chesapeake Bay have both been plagued by severe nutrient pollution and algae 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 from nutrient pollution from the Mississippi Basin.

Subsurface drainage can also affect the hydrology of a watershed by altering flows and increasing erosion, which has the potential to alter the course of a stream and lead to flooding and damage. to wetlands. These changes can affect the habitats of aquatic species, and flooding can also end up impacting other agricultural lands along rivers and streams.

Interestingly, climate change is leading to increased use of subsurface drainage in some areas. For example, many Midwestern farmers whose crops are inundated by extreme rainfall have chosen to install underground drainage systems to deal with such changing and unpredictable weather conditions. In Illinois, more than 10 million acres have been tiled, accounting for 35% of its cultivated land. In Indiana and Ohio, as much as 50% of cropland is tiled.

Given the potential for environmental damage, it becomes all the more important to understand and regulate the use of subsurface drainage systems in a watershed, including identifying areas where subsurface drainage would cause serious environmental impacts.

Can tile drainage work for gardens and small farms?

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

However, beware of hobbyists: there are good reasons to be cautious in deciding whether to invest in tile drainage – or any type of drainage – for a backyard garden or even a small farm. The Internet is full of how-to videos on how to install these systems yourself. Don’t be fooled into thinking that anyone with a DIY background is equipped to build a successful drainage system on their own.

It is important to first know all the laws and regulations regarding the installation and maintenance of these systems in order to assess whether it is possible and legal to do so. And just like with large farms, it is necessary to find a qualified installer to ensure that such a system does not cause legal or financial headaches, or result in unintentional environmental damage. Once the unknowns, including costs, regulations, and field conditions are carefully explored, you are ready to make a feasibility assessment.

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