Tile Drain Study
The tributaries to the St. Lawrence River within the Raisin Region Conservation Authority (RRCA) watershed have been identified as significant contributors to elevated pollutant levels in the littoral zone of the river, primarily as a result of the heavy nutrient loading from agricultural inputs. Following discussions with local landowners, the RRCA embarked on a study in 2001 with the voluntary participation of a group of environmentally friendly landowners to examine the nutrient loss from cropped land through the tile drain outlets. It was felt that by adjusting farming practices to reduce nutrient loss from the fields, there may be an economic benefit to the landowner in fertilizer costs and an environmental benefit with reduced nutrient loadings in the waterways.
The objectives of the project are threefold:
- Confirm that drainage effluent from the tile drains is contaminated with nutrients from applied fertilizers and manure
- Determine how the nutrient and bacteria concentrations in the drainage effluent compare with recreational guidelines using the Provincial Water Quality Objectives (PWQO) as a measure.
- Develop a simple and effective technique to reduce nutrient loss from the landowner’s fields.
The landowners participating in the study were located throughout the RRCA watershed and provided detailed site information in the initial design and have been recording relevant information including crop yields and fertilizer application rates. The RRCA has been conducting the data collection and providing analysis.
Water quality data was obtained on a weekly basis when the tiles were running and analyzed for a range of parameters. Observations have been that tile outflow is generally restricted to the spring runoff period and wet weather during the fall. Summer storm events must be of sufficient intensity and duration before tiles are observed to be running. Some difficulties have been experienced at some sites with the submergence of the tile outlet within the drain flow, preventing the collection of effluent samples.
Soil samples were taken before fertilizer and manure application in the spring. If the manure was to be spread, a sample was taken to be analyzed to determine the nutrient concentrations present. Soil sampling was undertaken again in the late fall after harvesting. Sampling data and some interpretation of the results were summarized into a report and distributed to the participating landowners annually providing them an opportunity to make adjustments to their application rates based on parameter levels measured in the soil and water. Valves were installed at the tile drain outlets at some sites to investigate their ease of installation and operation.
Data collection over the years confirms that the drainage effluent from the tile drains generally contains elevated levels of a number of nutrients including Total Phosphorous and Nitrates and bacteria such as E. Coli with levels often exceeding the PWQO recommendations. These nutrients and bacteria tend to enter the watercourse during the high flow periods in the spring and fall and occasionally following severe summer storm events.
Although close monitoring of nutrient levels in the soil provides a feedback mechanism to the landowner for adjusting application rates, the installation of a valve at the outlet of the tile drain affords additional opportunities to manage flows from tiles to the adjacent watercourse. Between spring and fall when soil moisture is low enough for machinery to be on the fields, is a period where the water and the component bacteria and nutrients within the soil can be retained within the cropped land if a valve at the drain outlet is in place.
Recommendations from the Tile Drain Study include continuing the monitoring of tile outlets and soil values to capture data during diverse conditions and including Tile Management as a component of the Beneficial Management Practices to be considered for landowner assistance under the Tributary Restoration program.
Information on Tile Drain Management is available for download. For additional information, please contact: Normand Genier - Soil and Water Conservation Specialist. firstname.lastname@example.org or Chris Critoph - Manager of Environmental Services. email@example.com.