First- and second-generation agrometeorological models for the prairies and simulated water-demand for potatoes

Abstract

On the Canadian prairies, moisture is usually the limiting factor in crop production. Occasionally, the thermal regime limits yields. At the Winnipeg Climate Centre, Environment Canada, a root-zone water-balance model simulates crop development, water-demand and water-use with daily climatological observations from across the agricultural portion of the Canadian Prairie Provinces. Simulations are used for regional-scale monitoring of the prairie's major crops (spring wheat, barley and canola) and they have been used to quantify climatological risks. This agrometeorological model is termed a first-generation model as potential evapotranspiration is estimated empirically from Baier and Robertson's simplest regression equation. A coupled atmosphere-crop-soil agrometeorological model has also been developed for crop monitoring on the prairies. This model generates atmospheric boundary layer profiles at climatological-sites using upper-air analyses and surface characteristics. The crop-soil boundary layer consists of the growing crop, and the top, root and sub-zones of the soil. Evapotranspiration is calculated deterministically from the air's water vapour density deficit. The calculation is modulated by aerodynamic, canopy and soil resistances. The coupled approach is termed a second-generation model. The re-formulation of the coupled model to simulate the phenology and water-demand of a newly significant crop, potatoes, is described. Comparison with 1994 and 1995 test-plot observations of fractional leaf area and rooting depth suggests that the potato phenology simulation requires further development. Estimates of daily crop water-demand are similar but show greater day-to-day variation than values generated by a first-generation Baier and Robertson procedure.