Slave Lake Pulp Site

Field plots were established in 1992 to evaluate the impact of land application of sludge and ash materials from SLP on soils and vegetation. The experiment included:

  • 6 x 12 m plots
  • 3 replicates
  • 6 treatments: control (0 cm), 1 cm (16 BDT/ha), 3 cm (48 BDT/ha), 5 cm (80 BDT/ha), 5 cm/yr for 3 years (multiple application treatment) and a combination of 5 cm sludge and 0.5 cm wood ash (50 t/ha)
  • Sludge incorporated by rototilling to 15 cm depth
  • Plots seeded to Brome Grass and fertilized in 1992 (35-15-0)
  • Pre and post sludge application soil samples were obtained to determine pH, carbon (TC, TOC, TIC), nitrogen, C:N, CaCO3 equiv, exchangeable cations, CEC, EC, SAR, soluble ions (HCO3, CO3, Cl, NO2, NH4, Sr, Ba, P, S, Mg, As, Si, V, Na, Mo, Se, Al, Ca, Zn, Cu, Pb, Li, Ti, Cd, Co, Ni, B, K, Mn, Fe, Cr)
  • Yield assessments and plant tissue analyses (DTPA extractable and total elements) on Brome Grass


  • Original soil was a Luvisolic soil: LFH, Ahe, Ae, Bt
  • Soil analyses indicated soil-sludge mixtures rated fair to good relative to soil quality criteria guidelines
  • Slightly ↑  pH one year after application, subsequently decreased
  • ↑ SAR with increased application rate
  • Total N ↑ slightly after sludge application and remained elevated for up to 3 years
  • TOC ↑ in all treatments after sludge application up to 3%
  • 50% ↑ in P with 5 cm sludge application
  • 50% ↑ in Ca with ash application


  • The sludge had a strong fertilizing effect on the grass, especially at the 3 cm and 5 cm application rates.
  • No statistical difference between 1 cm sludge application and control.
  • Sludge fertilizer effect diminished 4-5 years after application, warranting reapplication.
  • Number of reapplications should be limited based on SAR
  • Several soil chemical parameters initially increased in the first year after sludge application and subsequently decreased.
  • The sludge had no impact on tissue concentration with the exception of B and Na which were elevated to normal levels for grasses.