UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Influence of sewage sludge application on hydraulic and physical properties of a silty clay loam subsoil Kodsi, Elias G.


Turf growers have been farming the Ladner soil in the Boundary Bay area for the last decade. At each harvest, approximately a 2cm layer from the A horizon is taken out with grass. Consequently, the cultivation layer is becoming thinner year after year and the growers are already cultivating the B horizon. The possible improvement of the B horizon structure through sewage sludge application will benefit the fanners in the area. A greenhouse experiment was conducted using a Ladner subsoil. Treatments included application rates of 0, 33, and 100 t/ha of composted sewage sludge. The effect of sludge application on the soil structural stability in relation to the destructive action of water was evaluated. Soil columns were subjected to periodic 24-hour simulated ponding events. Adding sewage sludge increased the ponding tolerance of the soil. This was reflected by statistically significant differences in satiated hydraulic conductivity ('Ks') between the sludge-amended columns and the control columns. The significant decrease of 'Ks' of the control treatment as a result of ponding was responsible for widening the gap between 'Ks' of the control columns and 'Ks' of the sludge-treated columns. The incorporation of sewage sludge slowed down the decrease of 'Ks' but could not stop it. The most plausible explanation is that the addition of sewage sludge was effective in increasing the resistance of aggregates to breakdown when subjected to ponding. Fifty days after the last ponding event, the percent stable aggregates averaged 13.7, 26.9, and 48.1% for the 0, 33, and 100 t/ha treatments respectively. In no case was a significant difference in bulk density observed between the treatments. The soil structure deterioration as a result of ponding was not reflected by the bulk density measurements. Thus, it was concluded that hydraulic conductivity and aggregate stability are better idices of soil structural deterioration than bulk density. A side investigation was carried out to illustrate trends of essential nutrient and heavy metal uptake by bermuda grass. Sludge incorporation at 33 t/ha did not seem to increase nutrient and metal uptake by bermuda grass. However N, Cd, and Zn uptake appeared to increase at 100 t/ha.

Item Media

Item Citations and Data


For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.