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.
- 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.