Predicting consumptive use of water by irrigated crops in Manitoba
Prediction equations were developed for daily latent evaporation (evaporation from the black Bellani plate atmometer) and evaporation from a U.S.W.B. Class A pan from meteorological data (observed at the experimental station) and astronomical data. Multiple regression analysis showed the correlation coefficients for latent evaporation equations are considerably more reliable than those from the Class A pan. Prediction equations for daily latent evaporation were selected for this study. These equations were compared with those of Baier and Robertson (1965) and it was found that only one of their equations (Method VII) can be applied meaningfully to the Carberry area. The ratios of consumptive use to evaporation for various crops grown at Vauxhall, alberta and reported by Sonmor (1963) were investigated and it was found that they can be transferred to some areas in Manitoba. The seasonal consumptive use in inches for four major crops estimated using black Bellani plate ratios developed for Vauxhall was as follows: alfalfa, 20.6; sugar beets, 15.6; potatoes,14.1; and wheat, 14.0. These figures are much lower than the values reported for Vauxhall by Sonmor (1963) and at Swift Current by Pohjakas (1966). This is probably due in part to the unusual 1969 summer weather which was slightly cooler than normal years.