Variable thermal crop water stress index reference temperatures for irrigated spring malt barley in a semi-arid climate

Authors: King, Bradley - Brad; Rogers, Christopher; Tarkalson, David; Bjorneberg, David - Dave

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/1/2023
Publication Date: 7/20/2024
Citation: King, B.A., Rogers, C.W., Tarkalson, D.D., Bjorneberg, D.L. 2024. Variable thermal crop water stress index reference temperatures for irrigated spring malt barley in a semi-arid climate. Meeting Proceedings. 2400163; 1-27. https://doi.org/10.13031/aim.202400163.
DOI: https://doi.org/10.13031/aim.202400163

Interpretive Summary:

Technical Abstract: Application of canopy temperature-based crop water stress index (CWSI) for monitoring plant water stress and scheduling irrigation requires reliable estimation of well-watered (TLL) and non-transpiring (TUL) canopy temperatures under identical climatic conditions. A 3-year field study was conducted to develop and evaluate the use of data driven models to estimate TLL and TUL of irrigated spring malt barley. Five irrigation rates with four replicates each were used: full irrigation (FIT), 75, 50 and 25% of FIT and no irrigation. Three replicate continuous canopy temperatures measurements were taken in each irrigation treatment starting the first week in June ending in mid-July along with meteorological conditions. A feed forward neural network (NN) model was used to predict TLL between 13:00 and 15:00 MDT based on model inputs: solar radiation, air temperature, relative humidity, and wind speed for the same period. A physical model calibrated to the data set was used to estimate TUL. The NN model predicted TLL was well correlated with measured TLL (R2 = 0.99) with root mean square error 0.89 degrees C and mean absolute error 0.70 degrees C. There were significant differences in calculated daily average CWSI between irrigation treatments. Relative evapotranspiration, relative malt barley seed yield and percent plump kernels were negatively correlated with season average CWSI. Malt barley seed test weight was positively correlated with season average CWSI. The relationship between daily average CWSI and fraction available soil water was well described by a two-parameter exponential decay function (R2 = 0.72). These results indicate applicability of data driven models for computing CWSI of irrigated spring malt barley in a semi-arid environment and demonstrate malt barley yield response to crop water stress.