Riverine nutrient concentrations respond to upgradient greenhouse agriculture
Timothy Maguire, Great Lakes Institute for Environmental Research, University of Windsor, [email protected]
Katie Stammler, Essex Region Conservation Authority, [email protected]
Scott Mundle, Great Lakes Inst. for Environmental Research, [email protected]
Christopher Wellen, Ryerson University, [email protected]
Abstract
Greenhouse vegetable production is a globally significant sector that generates a billion dollars in produce annually from the United States and Canada. Limited information is available differentiating dissolved nutrients delivered from greenhouses and regional agricultural sources through riverine systems into Lake Erie. Water from 14 predominantly agricultural rivers were sampled bimonthly over 5-years in southwestern Ontario. Five river watersheds were subject to traditional agricultural practices of the area (soy, wheat, and corn), the remaining nine had some proportion of their watershed used for greenhouse agriculture. Nutrient regime is significantly different between river types. Rivers with greenhouse activities had mean annual concentrations of nitrate (NO3), phosphate (PO4), total phosphorus (P), and potassium (K) at 8, 28, 20, and 6 times higher than rivers without greenhouses, respectively. Greenhouse river NO3, P, and K concentrations significantly decreased during the 5-years of sample collection while concentrations in rivers without greenhouses remained constant. Decreases in greenhouse rivers are attributed to precipitation and dilution and not within watershed nutrient source changes. The Great Lakes Water Quality Agreement calls for 40% reduction in P loadings to the Lake Erie western basin, our work shows that greenhouse are a missing facet of regional nutrient export budget.
1. Keyword
nutrients
2. Keyword
pollution sources
3. Keyword
Lake Erie
4. Additional Keyword
riverine
5. Additional Keyword
agriculture
6. Additional Keyword
greenhouses