Greenhouse Trials

Objective:

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

Results

  • 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 

Conclusions

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