Crop ET Monitoring and Impact of Deficit Water Supplementation.

The development of modern cultivars coupled with weather variability necessitate local quantification of crop evapotranspiration (ETc). Local ETc linked to crop growth and development will provide a basis for prioritizing irrigation supplementation with the goal of deficit supplementation. The objectives were to 1) characterize ET of hard red spring wheat (HRSW), barley, and canola, and 2) increase water use productivity of responsive wheat cultivars with deficit irrigation. Eddy covariance towers were used to monitor water and CO₂ fluxes from 2015-2017 on farmer fields. Research plots for HRSW water productivity were also investigated in 2014 (average rainfall) and 2015 (a drought year). We investigated six water regimes including 1) rainfed check, 2) 100% ET, 3) 66% ET, 100% ET with final irrigation applied at 4) flower, 5) early milk, and 6) medium milk. Eight HRSW cultivars were used to screen for consistent productivity response in each of the contrasting growing seasons. Results showed that deficit irrigations of 66% ET and the final irrigations applied at early milk and medium milk did not negatively impact wheat yield as compared to 100% ET. These treatments increased water productivity. Results indicate at least one irrigation event needs to be applied within the grain-fill period. Peak crop ET using eddy covariance seems to follow with the critical crop development. Analysis with the crop ET in relation to the less critical end-of season irrigation omission will be presented.