Roots in Subsurface Drains
Larry Brown
  

Each year we receive dozens of calls about plant roots getting into agricultural subsurface drains. If not corrected in a timely fashion, these problems may grow into very large problems. Even 16-inch tile can get plugged.

The primary reason why plant roots grow through the slots between clay tile, and through the perforations in corrugated plastic tubing, is that they seek water. If there is standing water or flow of water (even a small flow) in the drain, producing an available water supply, plant roots will seek it out when the upper layers of the soil are dry. For the most part, there has to be some water there for the plant roots to seek it out, but most non-hydrophytic plants will not grow into total saturated soil conditions. Also, most non-hydrophytic plants will not send roots out into large, open voids, like a drain pipe. Hydrophytic plants are water loving plants that can grow in saturated soils. So, if a little constant wet spot in the drain is present at the right stage of the crop, or even a little trickle that is somewhat constant, the plant will seek the water.

Why does water stand in a drain pipe? Poor drainage system installation and the deterioration of an old tile system are two obvious reasons. Also, there might be a situation where spring water or pond water overflow containing algae, aquatic weeds, or plant seeds enters the drain. These problems become worse when there is water flow, even a trickle, during the growing season, particularly during very dry periods.

Also, consider conditions where a small constant water flow in the drain occurs (including high water vapor conditions), and the plant may send out numerous small roots. The water source dries up and then there are bunches of small roots extending into the drain. At any one point along the drain there may be no problem. If small roots grew into a very long stretch of drain, for example, and then there was a large rainfall event and subsequently drain flow, these roots would most likely be sheared off and flushed downstream in the drain. At some point downstream in the drain there may be enough accumulation of these sheared-off roots that they start to settle out in the drain, and then a blockage occurs.

Sewage drain no-no's
Another possible contributor to plugging may be connecting an overflow or outlet from an on-site sewage disposal system to agricultural drains. Besides providing a near constant water supply (daily water use from household equals constant water supply), this partially treated wastewater contains plant nutrients. Outflows from a septic system, including curtain drains, should not be tied into agricultural subsurface drains. Agricultural drains are not designed for this purpose.

Excavation or high-pressure cleaning
To identify and correct these types of problems, a drain may have to be excavated. It is important to determine if there is a somewhat constant stream of water that runs through the drain, and/or if there is a dip in the drain where water and sediment collect. If there is septic system discharge into the drain, this wastewater overflow should be removed from the agricultural drain and routed elsewhere. Sometimes reinstallation of a portion of the drainage system may be required.

In other cases the drain may just need to be cleaned. I do not suggest any type of chemical cleaning. Copper sulfate, and other chemicals, may harm some aquatic species in streams and ditches if the concentrations are large enough. Although this may work temporarily, I do not believe is is worth the environmental risk.

For cleaning, I suggest contacting a high-pressure, drainage pipe/sewer cleaning company. These companies have tools that cut through large root masses and sprayers to wash out the drains. Drain cleaning will be demonstrated at the August 4th Field Day at OSU's OARDC North Central Research Station, near Fremont, Ohio.

Larry Brown, Professor and Extension Agricultural Engineer, can be reached at 614-292-3826, or brown.59@osu.edu

 

 

This column is provided by the OSU Department of Food, Agricultural, and Biological Engineering.