Dominant glacial landforms in the lower Great Lakes region exhibit different soil chemistry and potential risk of phosphorus loss

Transcription

1 Dominant glacial landforms in the lower Great Lakes region exhibit different soil chemistry and potential risk of phosphorus loss J. Plach, M. Macrae, M. Williams, B. Lee, and K. King JANINA PLACH University of Waterloo

2 Water Quality in the Great Lakes Region Lower Great Lakes Region Phosphorus (P) losses economic & environmental concern crop productivity & water-quality Photo: NASA Cyanobacteria blooms Lake Erie Agricultural tile-drain Landscapes Eutrophication - harmful algae blooms & hypoxia; P -limiting nutrient Management evaluate processes controlling soil P mobility predict risk of P losses & design best management practices (BMPs) Tile Drainage Algae P Edge-of-field P lake Down-stream

3 Tile drain P losses in the Great Lakes Region Particulate P Lake Erie Lake Erie August 2017 Soluble Reactive (SRP) Photo: NOAA Why regional differences? 1. Management (e.g., P application)? 2. Landscape variability in soil type? Tile Drains Tile Drains

4 Soil types in the Great Lakes Region Clay soils Loam-soil (hummocky, coarse textured glacial till) Clay-soil (flat, fine-textured till) Source: Photo: NOAA Matrix flow P Preferential Flow Tile Drainage Soil Type 1. Water flow paths 2. SoilTile P retention Drains

5 Risk of P loss from soils 1. Storage of soil inorganic-p (P i ) P i 2. Mobility potential of soil P i Reactive substrates e.g., Minerals (abundance, type) Solubilize P under changing soil conditions: Grain size (soil texture), Composition (organic, carbonates, oxides), ph Hydrology (e.g., matrix, macropore, soil erosion) organics P mobility & fate, availability to crops & runoff

6 Project Objectives Photo: V. Lam Are there natural differences in landscape sensitivity to P losses? 1. Storage of P 2. How tightly is P held in different soil types? Comparing agricultural croplands in lower Great Lakes region of Ontario, Canada & USA

7 Study Sites Hummocky, coarse-textured till landform Hummocky Ilderton ONT Lake Ontario Hummocky St Mary s ONT Flat, fine-textured landform 8 Fields Similar management, C-S-W rotation up to 36 inches (tile depth) Flat, clay Essex, ONT

8 Soil Analysis Soil P i Fractionation Homogenize Soil Key Parameters Composition, ph Texture (sand%, silt%, clay%) Soil test, STP (Olsen, Bray, Mehlich) Soil P i fractionation LOI, Carbonates Soil- Fe

9 Soil Analysis Soil P i Fractionation Homogenize Soil Loosely-bound Reducible-bound Calcium-bound Total Soil-P i Residual-bound LOI, Carbonates Soil- Fe

10 Soil Texture Hummocky, coarse-textured landform loam low shrink-swell matrix flow clay high shrink-swell preferential flow Flat, fine-textured landform Higher shrink-swell

11 Soil inorganic P (P i ) pools Loosely-bound Reducible-bound Calcium-bound Hummocky, coarse-textured landform Residual-bound 1. Silt loam Silt Loam 2. Depth (inches) Clay Clay Clay Flat, fine-textured landform Clay

12 Soil Composition Hummocky, coarse-textured landform Calcareous alkaline low-carbonate slightly acidic Flat, fine-textured landform

13 Up-slope Ca-P i Slope Patterns Ontario- Silt Loam Mid-slope Down Up-slope Photo: R. Carlo Photo: R. Carlo Mid-slope Down-slope Loosely-bound Reducible-bound Calcium-bound Residual-bound

14 Manitoba Soils Ca-P i Slope Patterns Ontario- Silt Loam AWF: Dr. Henry Wilson Agriculture and Agri-Food Canada Up-slope Porewater: soil-water interactions Mid-slope Down-slope Loosely-bound Reducible-bound Calcium-bound Residual-bound

15 Summary and Implications 1. Clear difference in water quality between landscapes 2. No difference total soil P i, BUT different soil P speciation 3. Mid-western Ontario, P bound more tightly Ca-P Higher natural buffer capacity (carbonate, alkaline) Potential for matrix flow in subsurface Tile P loss- landscape driven? Design region-specific management Photo: V. Lam

16 THANK YOU! Funding: Grain Farmers of Ontario (GFO), Agricultural Adaptation Councils (AAC) and LICO Logistical Support: K. Nixon, L. Taylor, B. McIntosh Field & Lab Support: V. Lam, K. Grant, M. Morison, K. Hanke, J. Cober

17 QUESTIONS? Janina Merrin