Experiments conducted by Alberta Innovates: Technology Futures show very positive results for spreading sludge in forest settings.

The Forest Cut-Block Trial determined that

  • Sludge treated plots have increased heights, diameters and stem volume compared to the control treatments.
  • It is predicted that at age 25, Pine tree volume in the sludge application will nearly double the stem volume in the control treatment.  Spruce trees show similar results.

The Cut-block Seedling/Sucker Trial showed that

  • Tree volumes for Aspen, Balsam and Spruce were greater in sludge treated areas.
  • An application rate of 50 t/ha (BDT) is recommended as opposed to the 85 t/ha to reduce the effect of competition from competing species, increase seeding survival rates and growth and minimize the risk of nutrient losses due to leaching.

The Juvinile Forest Trial found that

  • Spreading sludge in juvenile stands can be more effective in achieving long-term productivity than spreading prior to tree planting.

The Spread Without Incorporation on a Slope Trial found that

  • Seedlings that were planted in more dense grass covers demonstrated less vigor than those in open areas.

The Winter Applied Slope Trial found that

  • Surface water sampling conducted indicated that the applied sludge had no effect on surface water quality in the small temporary depressional areas downslope from the treated areas. 
  • The stream samples collected indicated that there was no impact on water quality below or downstream from the sludge treatment areas.

The Operational Suckering Trial reasserted that

  • Sludge application resulted in a substantial change particularly in diameter and the resultant stemwood volume.

The Operational Spreading Trials at Block 1018 and Block 1047 showed that

  • Although there was a difference between the sludge treated areas and the control, there was very little difference between treatments, which was likely impacted by the application process.
  • Field observations indicated that pine trees in the sludge amended treatments were a deeper green color and showed better growth than those in the control plots.