Final report on crop coefficient development for canola and dry bean in Saskatchewan to improve yield and water use efficiency.

A three-year study was initiated in the 2018 growing season to determine the crop evapotranspiration (ETc) of canola (Brassica napus L.) and dry bean (Phaseolus vulgaris L.) and to develop the crop coefficients (Kc) for the two crops in Saskatchewan (SK). Field data were collected on two private farms each year, one for canola and the other dry bean. In 2018, both fields were located northeast of Outlook, SK. In both the 2019 and 2021 growing season, the canola fields were located southeast of Outlook SK, while the dry bean fields were southwest of Riverhurst, SK. A Bowen Ratio Energy Balance System (BREBS) was used on each field to collect data for determining daily crop evapotranspiration of each crop at all sites. The FAO56 Penman-Montieth equation was used to calculate the reference evapotranspiration (ETo) using data collected from the Environment and Climate Change Canada (ECCC) meteorological station at Outlook. A seasonal evapotranspiration of 320, 313 and 307 mm was determined in the 2018, 2019, and 2021 growing season, respectively for the dry bean. The range of daily evapotranspiration for the dry bean was 1.3 to 7.9 in 2018, 0.6 to 8.3 in 2019, and 0.6 to 9.3 mm in 2021, and the mean daily values were 3.9, 3.4, and 3.7 mm, respectively. The grass-reference crop coefficient, Kco, and alfalfa-reference crop coefficient, Kcr, values developed for the dry bean ranged from 0.14 to 1.44 and 0.11 to 1.17, respectively, in the three-year study. Mean values of 0.35, 0.74, 1.16 and 0.69 were developed as the initial, development, mid-season and late-season stage Kco values, respectively, while 0.27, 0.59, 0.91, and 0.51 were developed as the initial, development, mid-season, and late-season stage Kcr values, respectively, for dry bean in Saskatchewan. Fourth-order polynomial equations were developed for estimating Kco and Kcr in terms of cumulative growing degree days (CGDD), and power function equations were developed for estimating Kco and Kcr in terms of leaf area index (LAI) for dry beans. The seasonal evapotranspiration determined for canola was 399 and 420 mm in 2019 and 2021, respectively (the crop in the study area failed in 2018). The daily evapotranspiration for canola ranged from 0.4 to 7.2 mm and 0.9 to 9.4 mm in 2019 and 2021, respectively, with the mean being 4.0 and 4.7 mm respectively. The canola Kco and Kcr values developed using the last two-year data ranged from 0.10 to 1.38 and 0.07 to 1.19, respectively. Mean Kco values of 0.35, 0.91, 1.17, and 0.78 were developed as the initial, development, mid-season and late-season stage value for canola, while 0.27, 0.71, 0.91, and 0.56 were respectively developed as the canola Kcr value for initial, development, mid-season and late-season stage, respectively. Based on multiple regression analysis, third-order polynomial equations were developed for estimating Kco and Kcr in terms of CGDD for canola.