A prototype of decision support system entitled Residue Recommendation System (RESREC) has been developed to predict changes of crop residue with time in cropping systems typical of Western Canada. The system uses the Douglas/Rickman model to simulate decomposition, and tillage coefficients to
calculate the effects of field operations on residue levels. Decomposition is simulated by calculating the loss based on an empirical relationship to long-term means for air temperature, the nitrogen content of the crop residue, and placement of the residue. Overall, the nitrogen content was correlated with decomposition rates of spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.),
canola (Brassica napus L.), and flax (Linum usitatissimum L.) straw and alfalfa (Medicago sativa .L.) hay. Overwinter loss of crop residue varied considerably between crops and further research is required to quantify these rates.