Kensington North Watersheds Association
(2013-07-09) Last fall, with funding from the Environment Canada Eco-Action Program and techical support from Agriculture and Agri-Food Canada and PEI Dept. of Agriculture and Forestry, KNWSA constructed a bio-reactor to capture nitrates from tile drainage in a small tributary to Darnley Basin. We had previously planted trees in this same small riparian zone on the property of Hickey Farms in Darnley and thought the location would be a good site to demonstrate this new technology.
The bio-reactor is essentially a 40 ft. long trench, 4 ft. wide and 4 ft. deep, lined with polyethylene plastic and filled with wood chips. Water from the field tile enters and exits the pit via special control structures that regulate the water level in the bio-reactor. The wood chips, nourished by nitrates in the water, are host to a microbial population that consumes up 50 to 80% of the nitrates. The water leaves the bio-reactor and enters the riparian zone in a cleaner state.
The graph to the right shows the results of seven months of testing. The trend lines appear to show the effect of temperature on microbial action with generally higher test results and a smaller spread in the colder months and a marked increase in effectiveness in the warmer months.
The bio-reactor installed in this watershed is a demonstration of how wetlands play a significant role in recycling lost nutrients from agricultural lands within our watershed. By mimicking a wetland's ability to filter out excess nutrients from the water that flows through the wetland, the bio-reactor acts as a demonstration of the purifying role wetlands have within our water ecosystems and provides the ability to quantify the amount of nitrates that are reduced within the system at the same time. As water flows through a wetland, plant material is actively decomposing into nutrients required to make new plant material and organic matter. Wetlands are able to slow down the movement of water throughout the system, allowing more nutrients to be used for living organisms and new plant matter within the wetland before excessive nutrients can be lost to surface and groundwater sources. In this capacity, wetlands provide a valuable service in recycling lost nutrients from nearby agricultural lands by reducing the potential of surface and groundwater contamination within our watershed.
Maintenance of wetlands within this watershed can aid in reducing excess nitrates within our system, and will be necessary in order for us to achieve our goal of reducing nitrate levels in our ground water and surface water. The obvious nutrient benefit that wetlands add to these systems is but another important role that wetlands play in a farm operation.
Nitrates have been identified as major contributors towards the growth of excessive blooms of sea lettuce in our estuaries (where the salt and fresh water meet) which in turn leads to harmful anoxic events. Sources of nitrates include septic systems, manure, chemical fertilizer, industry, and residential waste management systems. Kensington North has a Nitrates Stakeholder Committee, made up of residents, farmers, and developers, that are thoroughly reviewing all things concerning nitrates in the upper Southwest River watersheds. The Committee has completed an Adaptive Plan to Reduce Nitrates in the Upper Reaches of the Southwest River. The plan can be read by clicking here.
One part of the plan called for the assistance of an agronomist to help local farmers with nutrient management. KNWSA along with the PEI Federation of Agriculture applied for funding from the PEI Adapt Council. An agronomist, Harvey Cairns, is now working part time and has several nitrate reducing initiatives underway. Updates on Harvey's contribution will be posted from time to time on his blog, Nutrient Management Planning.
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|Last updated: 2013-07-09|
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