Juvenile Forest Trial 


To evaluate the impact of sludge application without incorporation on juvenile pine stands and soil quality.


The Juvenile Forest Trial was located at NW-32-58-18-W5 on an experimental site adjacent to the existing forest cut block experimental site.  The experiment included:

  • 11 plots in 3 locations
  • Sludge was applied with the Aero-Spread® unit in 1998 at applications rates ranging from 26 to 63 t/ha
  • Baseline soil samples were collected in 1998
  • Post sludge application samples were collected annually until 2002 
  • 300 trees were tagged in the sludge amended areas and 250 trees were tagged in the control areas. 
  • Baseline measurements for tree diameter and height were taken prior to sludge application and measured annually from 2001 to 2007 and again in 2010.


  • Tree volume, heights and diameters in the sludge amended areas were substantially greater than the control.
  • Tree height and diameter age shift and growth multipliers indicate that sludge treatment has a significant effect on vegetative performance, for example, trees growing in the control treatment will require an additional 4.9 years to reach the same height as trees growing in the sludge amended plots.  

Results and Conclusions

  • The Juvenile Forest Trial Area 3 was compared to the 50 t/ha sludge application treatment (D5) in the Forest Cut-Block Trial (located approximately 60 m apart) and the results demonstrate that spreading sludge in juvenile stands can be more effective in achieving long-term productivity than spreading prior to tree planting. 
  • The physical size of the trees in the juvenile stands and the established root systems can effectively utilize the available nutrient pool.
  • A greater portion of the available nutrients is likely used by the established trees than by the competing understory.  
  • In the case of newly planted seedlings, their capacity to utilize the nutrients in the sludge would be limited, thus a larger portion of the nutrients are available to competing species, especially grasses.    
Area Application Rate (t/ha) Age Shift Growth Multiplier
 Height Diam Height  Diam 
 ANC Juvenile Forest Trial 58 4.9 8.3 1.19 1.40