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Although the Living Lab – Atlantic project ended in 2023, its legacy continues as positive research results continue to pour in, highlighting how farmers and researchers are working together to improve water quality. Soon after, a second Living Lab launched on Prince Edward Island as part of a network of 14 living labs under the Agricultural Climate Solutions – Living Labs program at Agriculture and Agri-Food Canada (AAFC).
When you’re surrounded by the ocean, soils tend to be sandier than more inland provinces. Water can enter groundwater more quickly in sandy soils and then migrate to nearby waterways. Because of this, farming practices can have a direct impact on the water quality of the limited freshwater streams and rivers that feed into brackish estuaries and eventually the ocean.
While there are many important practices that farmers already use to help maintain healthy waterways, AAFC research scientist Dr. Yefang Jiang, based at the Charlottetown Research and Development Centre, set out to use soil and water modelling data to find out how various in-field beneficial management practices could help reduce nitrogen from entering groundwater and improve surface water quality in streams, lakes, and coastal areas. This research work involved Prince Edward Island farmers along with collaborators from the Canadian Food Inspection Agency, Fisheries and Oceans Canada, Environment and Climate Change Canada, and the Prince Edward Island Department of Agriculture.
“Ecologically, the whole Island is a living lab, and what happens on land affects what happens in the water. When we can also connect and collaborate with broader partnerships through living labs, we can understand how even small changes to farming practices can improve water quality.”
- Dr. Yefang Jiang, research scientist, Agriculture and Agri-Food Canada
Modelling for every season
Dr. Jiang and the team focused on farms in the Dunk River watershed in central Prince Edward Island as this region holds much of the province's farmland. Where water sampling typically occurs in summer months, the team used a model to simulate the sampling data from the fall, winter, and spring to determine the annual effects of nitrogen on waterways.
To understand how different crops contribute to nitrogen levels throughout the year in the Dunk River watershed, researchers adapted the Soil and Water Assessment Tool (SWAT) to local conditions to estimate how water, nutrients, and land use interact with the landscape over the course of a given year. This public domain model helps researchers across various government departments and academia estimate data more accurately to support land management decisions. It is useful in situations where large-scale watershed sampling is not practical due to logistics, cost, and the sometimes-long timelines needed to detect land use change effects on water quality.
“We applied the SWAT model that uses samples collected during the summer to predict what the nitrogen loading or excess nitrogen results would be in fall, winter, and spring. This provides a more accurate representation of annual nitrogen loading than the estimates based on summer sampling alone; while better reflecting the way farming practices are affecting water quality,” says Dr. Jiang.
How farmers can maintain healthy waterways
Researchers used the SWAT model, which was adapted using real-world local data, to serve as a virtual watershed, to test the effects that various on-farm beneficial management practices would have on water quality. It included studying the various crops used in farmers’ 3-year rotation with potatoes such as red clover, soybean, timothy (a perennial grass), and buckwheat.
Dr. Jiang found that red clover and other forage legume crops can result in excess nitrogen in soils that can enter groundwater and receiving waterways if it’s not utilized by the next crop. Forage legumes, such as red clover and alfalfa, are commonly planted as rotation crops to improve soil organic matter, break pest cycles, control weeds, and provide nitrogen for future cash crops.
Red clover is used on Prince Edward Island in potato–cereal–clover rotations. However, because red clover adds large amounts of nitrogen to the soil, applying fertilizer without properly accounting for this natural nitrogen source can provide more nitrogen than the following crop, in this case, potatoes, needs. This excess nitrogen can enter groundwater, eventually reaching rivers and estuaries. Previous research by Dr. Jiang also advises farmers to test their nitrogen levels in their soil to account for the nitrogen added by plowed-down red clover, helping to avoid over-fertilizing potatoes.
A promising alternative solution? Substituting red clover with soybeans in the rotation. Soybeans recycle less nitrogen into the soil, which in turn reduces the risk of it entering waterways. Soybeans offer farmers a dual benefit: environmental stewardship and economic return.
“Soybeans, timothy, or buckwheat are great alternatives to red clover and leave little nitrogen in the soil after harvesting. Through our SWAT model, we found that replacing red clover with soybean can help reduce excess nitrogen in the Dunk River watershed by as much as 17%. Soybeans can also give farmers a second cash crop with potatoes.”
- Dr. Yefang Jiang, research scientist, Agriculture and Agri-Food Canada
Researchers from Fisheries and Oceans Canada found that the nitrogen reduction in the watershed when replacing red clover with soybean in the rotation reduced levels of nitrates, a common form of nitrogen, in estuaries further downstream from the Dunk River by up to 8%. Additionally, the reduction in nitrogen can lead to a 24% decrease in average sea lettuce biomass in the upper estuary. Sea lettuce growth can cause harm to aquatic animal life when it decomposes and uses up dissolved oxygen, known as anoxic events.
This research highlights the complexity of the movement of nutrients in modern agriculture, and the importance of data-driven decision making. Red clover remains a valuable tool for soil health and productivity, but like all tools, it works best when used with precision. Many potato farmers, Dr. Jiang notes, are now reducing their fertilizer use, along with other beneficial management practices to help protect waterways, while also maintaining yields.
It’s not just land and waterways that are interconnected on the Island, the living labs project continues to connect farmers with researchers through Living Lab – Prince Edward Island to co-develop and test innovative beneficial management practices that reduce greenhouse gas emissions, as well as improve soil and water quality, and biodiversity.
Key benefits and discoveries
- AAFC research scientist Dr. Yefang Jiang along with researchers from the Canadian Food Inspection Agency, Fisheries and Oceans Canada, Environment and Climate Change Canada, and the Prince Edward Island Department of Agriculture applied the Soil and Water Assessment Tool (SWAT model) to find out how various on-farm beneficial management practices could reduce nitrogen from entering groundwater and affect surface water quality in streams, lakes, and the ocean.
- The model helps researchers across various government departments and academia estimate data more accurately to support land management decisions in situations where large-scale watershed sampling is not practical due to logistics, cost, and the sometimes-long timelines needed to detect land use change effects on water quality.
- With SWAT, Dr. Jiang found that replacing red clover with soybean can help reduce nitrogen in waterways by as much as 17%. Soybean can also give farmers a second cash crop with potatoes.
- Researchers from Fisheries and Oceans Canada found that replacing red clover with soybean in the rotation also reduced levels in estuaries downstream from the Dunk River by up to 8%.
- The reduction in nitrogen can lead to a 24% decrease in average sea lettuce biomass in the upper estuary. Sea lettuce growth can cause harm to aquatic animal life when it decomposes and uses up the dissolved oxygen, known as anoxic events.
Photo gallery
AAFC research scientist Dr. Yefang Jiang sampling in one of the many waterways near agriculture fields on Prince Edward Island.
Using the newly developed SWAT model, researchers found that replacing red clover with soybeans in the crop rotation with potatoes can reduce nitrogen levels in rivers, streams and estuaries.