Supplemental spreadsheet for "Evaluation of Canopy Temperature based Crop Water Stress Index for Deficit Irrigation Management of Sugar Beet in Semi-Arid Climate"

Use of canopy temperature for deficit irrigation (DI) scheduling of sugar beet was evaluated in a 3-year plot study in a semi-arid climate. Four irrigation treatments were evaluated; full irrigation and three deficit irrigation treatments where an irrigation application of 25 mm was applied when an average daily crop water stress index (CWSI) threshold of 0.2, 0.35, and 0.55 was exceeded. There were significant irrigation treatment differences in seasonal evapotranspiration, soil water extraction, seasonal average CWSI, root yield, estimated recoverable sugar (ERS) yield, and water use efficiencies. Seasonal soil water extraction of the full irrigation treatment was significantly less than for the DI treatments in all study years. In 2021 and 2022, soil water balanced based evapotranspiration was significantly less for the DI treatments compared to the full irrigation treatment. However, there was no significant difference in root yield, ERS yield, and water use efficiencies between the full irrigation treatment and irrigating when daily CWSI exceeded 0.2 in any study year. The results indicate that irrigating when average daily CWSI sugar beet exceeds 0.2 is an effective means for mild deficit irrigation scheduling to reduce seasonal irrigation requirements with no significant effect on root and ERS yield.

Calculation of sugar beet CWSI was an integral part of this study. A neural network model was used to estimate non-water stressed canopy temperature. Documentation of the neural network model and its use to estimate non-water stressed canopy temperature are demonstrated in a Microsoft Excel spreadsheet. Calculation of non-transpiring canopy temperature is also demonstrated in the spreadsheet. The spreadsheet computes CWSI based on five inputs: solar radiation, air temperature, relative humidity, wind speed, and measured canopy temperature.