Four solum and subsoil materials from Alberta were treated to determine if soil aggregation and aggregate strength could be
increased to reduce succeptibility to soil compaction. Each soil was treated with organic amendments of manure or a control, chemical amendments of gypsum, bottom ash or a control, and cropping treatments of smooth brome grass (Bromus inermis), quack grass (Agropyron repens) or a control. Four replicates were used for each treatment. The grasses were grown in the amended soils for 23 weeks. The percentage of coarse, medium and fine aggregates in each treatment was measured, as well as the force required to crush large granular aggregates at moisture tensions of 1/3 bar, 1 bar, 3 bars and 15 bars.
All treatments favoured the development of fine aggregates at the expense of coarse aggregates. Across all moisture tensions only quack grass cropping significantly increased aggregate strength while bottom ash and manure amendments significantly decreased aggregate strength.
At 1/3 bar tension, at which aggregates have low strength and are easily crushed, all treatments significantly increased aggregate strength except the manure amendment wh i eh decreased strength. The results indicate that it may be possible to reduce the risk of soil compaction through effective land management.