Winter Applied Slope Trial
To assess the environmental impact of land application of sludge without incorporation in terms of soil quality and surface water quality in areas with slopes >5%, and on frozen, and frozen and snow covered soils
The Winter Applied Slope Trial was initiated by SLP in 2000 at NE and SE 27-71-4-W5. The trial included:
- Operational plots which received sludge in non-frozen, frozen and frozen – snow covered conditions
- 3 sludge application rates: 0, 30 or 60 t/ha.
- Extent of suckering, tree growth performance, and growth of understory cover were assessed
- Aspen suckers were tagged and measured in each of the sludge amended and control areas in 2000
- Measurements were obtained from 2001 to 2007 and in 2010.
Results and Conclusions
- Visual observations of the vegetation growth indicated that sludge application resulted in significant increases in vegetative cover.
- There was no indication of erosion or sludge loss after application as it was held on the soil surface by the vegetative cover.
- The largest difference in volume between the control trees and treatment areas occurred in the 60 t/ha snow and frozen application area, mainly as a result of the large difference in diameters.
- All other treatments showed greater volumes than the control, however were similar to each other.
- Soil samples indicated that the increases in EC, sodium content, and SAR levels were similar for all of the sludge amended plots.
- The largest change occurred in the surface (0 to 15 cm depth) and the underlying 15 to 30 cm depth intervals.
- Some leaching of sodium was evident down to the 1 m depth based on the SAR values ranging from 3.5 in the 15 to 30 cm interval, to 1.7 in the 75 to 100 cm interval.
- No observed increase in NO3-N levels or evidence of any leaching resulted from the sludge application.
- 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.
|Area||Application Rate (t/ha)||Age Shift||Growth Multiplier
|SLP Winter Applied
|Not Frozen 30||4.8||4.9||1.20||1.20|
|Not Frozen 60||-0.8||4.3||0.96||1.17|