Adapting the CATIMO grass model to meadow bromegrass grown in western Canada

The Canadian Timothy Model (CATIMO) simulates the growth and nutritive value of timothy grown in eastern and western Canada, Norway, and Finland, but has not been parameterized for meadow bromegrass (Bromus riparius Rehm.) grown under Canadian prairie conditions. We parameterized and evaluated the CATIMO model to simulate the dry matter (DM) yield and N concentration of meadow bromegrass grown in western Canada with data from sequential sampling in primary growth and regrowth from two field experiments for a total of 5 yr of observation. Primary growth DM yield was simulated well [R2=0.95; normalized root mean square error (NRMSE)=16%; model simulation efficiency (EF)=0.93]. Simulations of the regrowth DM yield (R2=0.49, NRMSE=39%, EF=0.47) were not as successful as that of the primary growth, but they were within expected ranges for regrowth DM yields in western Canada. Forage N concentration was poorly simulated in primary growth (R2=0.32, NRMSE=38%, EF=-0.95) and regrowth (R2=0.27, NRMSE=30%, EF=-2.43). Plantavailable soil moisture down to 30 cm was simulated well (R2=0.74, NRMSE=19%, EF=0.50). The parameterized model for meadow bromegrass expands the use of the CATIMO model to drier geographical areas where timothy may not be common, and it represents a first attempt to provide DM yield assessment of meadow bromegrass under Canadian Prairie conditions for whole-farm modeling.