| | Nutrients such as nitrogen and phosphorus are essential for plant growth. But when excess nutrients from decaying plants, soil, fertilizer and manure enter streams and waterways through runoff from snowmelt and rainstorms, they can reduce water quality. These nutrients feed aquatic weeds and algae, which can cause taste and odor problems and can deplete the vital oxygen reserves needed by other aquatic organisms.
To increase our understanding of how these processes vary across Alberta, a team of scientists, engineers, agronomists and technologists with Alberta Agriculture, Food and Rural Development, in cooperation with Alberta farmers, are conducting a three-year field study to compare in-stream nutrient levels to nutrient levels of surrounding cropped fields. "Through this study, we are extending previous phosphorus mobility research that was completed using a rainfall simulator and enough field data to interest us in finding out more." explains Sheilah Nolan, Research Agronomist, who is coordinating the provincial study with Water Quality Specialist Joanne Little. "We’re studying more real field conditions to fine-tune our understanding of the factors that influence how phosphorus enters streams in different Alberta conditions."
The researchers have ‘nested’ this study within watersheds that are currently being monitored for nutrient levels through the AESA (Alberta Environmentally Sustainable Agriculture) Water Quality Monitoring Program. "We’ve established six of our planned 12 'micro-watershed' field locations in uniformly managed fields within the monitored AESA watersheds," says Nolan. Two other sites were established outside of the monitored AESA watersheds to continue previous water quality studies. "We hope to relate our field data back to the watershed scale by also instrumenting intermediate-sized watersheds of multiple land use" adds Nolan. The 12 sites will represent different Alberta conditions, from the Peace region to Lethbridge. The study sites range in size from 30 to 200 hectares and were selected based on their runoff potential, ease of access for instrumentation. and uniform crop management. So far, only one site is irrigated, the others are all dryland.
A number of measurements will be recorded at the study sites including: rainfall, temperature and humidity, and detailed soil tests for nutrient levels. Soil samples will be taken by excavating a slice of soil, rather than collecting cores, to capture the wide range in nutrient levels caused by banding fertilizer and applying manure. Samples will also be taken at different landform positions in the field (e.g. knolls, midslopes and low lying areas), to measure the variation of phosphorus and nitrogen within the field. "Our objective is to understand how landform and climate affect levels of phosphorus and nitrogen moving off of the fields," says Nolan. "We know that nitrogen levels vary by landform, and we expect that phosphorus does as well. We also want to know how much each nutrient moves in the run-off."
"We’re quite excited about the instrumentation of the micro watersheds. We're using a ‘circular flume’ to measure water volumes," says Nolan. "These new state-of-the-art flumes are inexpensive, accurate and easy to use." Once the water level reaches a certain point in the flume, an automatic water sampler kicks in. Wireless Rom Comm technology then notifies the researchers by email or pager that samples have been taken. The water samples are then brought back to the lab and analyzed for nutrients. Funding for the automatic water sampling equipment was provided by AESA.
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| Circular flume installed in field |
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| Closeup of circular flume inlet |
"We’re using these innovative approaches to characterize the specific site and climate conditions in which different levels of phosphorus enter streams. We hope to use this information to move ahead on concerns such as identifying environmentally sound rates of manure and fertilizer that will maintain or improve water quality in Alberta, rates that vary according to landform and climate condition."
For more information, contact:
Sheilah Nolan
Joanne Little
Alberta Conservation Connection - Issue 18, Fall 2002 |
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