The Residue Recommendation System (RESREC), a decision support system, was used to predict levels of crop residue in crop rotations containing canola. Effects of decomposition and tillage on canola residue were simulated in conventional F-C-W-B and C-P-FL-B, and zero-till C-P-FL-B to provide estimates of temporal changes and formulate statistical hypotheses for field research currently conducted on the later two rotations at Melfort. Crop residue in the fallow phase of the FC-W-B rotation was less than that required to control soil erosion. Canola residue in conventional C-P-FL-B was rapidly reduced to less than 100 kg ha-1 by the combined effects of decomposition and tillage, but was maintained at a minimum level of 500 kg ha-1 in zero-till. Total minimum crop residue in zero-till C-P-FL-B was estimated at 3000 kg ha-1 but was near zero kg ha-1 in conventional tillage.