Agricultural Phosphorus by Watershed
Available phosphorus load for land application and soil saturation by watershed zone (ZGIEBV) in Quebec. Source: MELCCFP (~2018).
Agricultural phosphorus balances from Quebec's Ministry of Environment (MELCCFP) cover 40 watershed management zones (ZGIEBV) across the province, representing approximately 1.87 million hectares of farmland. The weighted average phosphorus load stands at 54.2 kg P2O5 per hectare, but variation across watersheds is extreme: from 8.5 kg/ha in the Duplessis basin (northern Côte-Nord, marginal agriculture) to 71.1 kg/ha in the Jacques-Cartier basin near Quebec City. This represents a sevenfold range between the most and least affected regions.
Quebec's agricultural heartland - Montérégie, Centre-du-Québec, and Chaudière-Appalaches - bears the heaviest pressure. The four highest-volume watersheds (Yamaska: 11,278 t P2O5, Nicolet: 8,168 t, Richelieu: 8,165 t, Saint-François: 7,491 t) account for 35% of the provincial load estimated at roughly 101,000 tonnes. Soil phosphorus saturation (% P/Al) - an indicator of long-term accumulation in topsoil - peaks in the Yamaska basin (8.9%), which is also the largest monitored agricultural watershed at 202,000 ha.
This dataset is a statistical snapshot published around 2018 by MELCCFP. The reported load represents phosphorus from animal manure available for land application - mineral fertilizers and other sources are excluded. Annual trend tracking and sub-provincial breakdowns are not available from the accessible data. The source dataset contains annual series (2012-2018) at the MRC level but these are not programmatically accessible.
71,1 kg/ha
The Jacques-Cartier watershed records Quebec's highest phosphorus load (71.1 kg P2O5/ha), 31% above the weighted provincial average of 54.2 kg/ha. Its agricultural area (8,735 ha) represents less than 0.5% of the total monitored zone.
8,9 % P/Al
The Yamaska watershed, Quebec's largest monitored basin (202,000 ha, 11% of total area), shows the highest soil phosphorus saturation (8.9% P/Al) despite a per-hectare load (55.7 kg/ha) lower than 8 other watersheds. Its estimated total load (11,278 t) represents 11% of the provincial balance.