Greenhouse Trials


To assess the effect of applying different rates of sludge on soil and plants and to determine the appropriate application rates for the field trials. 

Materials and Methods

Experimental variables included:

  • Two sludge types (de-ink and conventional)
  • Four application rates (2.5, 5, 10, 20 cm)
  • Three species (brome grass, lodgepole pine, white spruce)

Activities and Measurements:

  • Single application of fertilizer at time of seeding to equalize nutrients in all treatments
  • Moisture content maintained at 80% of field capacity
  • Four harvests, each after a 90 day growth period
  • Yield assessments and tissue analysis for each harvest
  • Extraction and analysis of soils from pots at completion of experiment


  • Increased grass yields and tree growth with sludge application
  • Soil loading limiting factors for sodium and nitrate leaching concerns reached at 20 cm application
  • Obvious differences between treatments and control in terms of height, root development, plant vigor, and leaf/needle colour 


  • Sludge is beneficial for enhancing plant growth
  • Field trials should be established with the highest application rate of 10 cm.