Malt barley yield and quality response to crop water stress index

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

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2024
Publication Date: 12/4/2024
Citation: King, B.A., Rogers, C.W., Tarkalson, D.D., Bjorneberg, D.L. 2024. Malt barley yield and quality response to crop water stress index. Applied Engineering in Agriculture. 14(12):1-16. https://doi.org/10.3390/agronomy14122897.
DOI: https://doi.org/10.3390/agronomy14122897

Interpretive Summary: Irrigated barley production in the intermountain region of the western U.S. (ID, CO, WY and UT) represents 30% of total U.S. production acreage and 92% of total U.S. irrigated production acreage with seasonal water use ranging from 400 to 650 mm. About three-quarters of barley production is used for malt production and must meet specific quality parameters established by the brewing industry based on the end-use. Crop water stress from drought or inadequate irrigation adversely affects malt barley quality. Precision irrigation management is required to malt barley industry standards. Irrigation management based on the thermal crop water stress index (CWSI) may be an effective tool to meet malt barley quality requirements under drought conditions. The specific objectives of this research were to use canopy temperature measured on fully irrigated and deficit irrigated plots with data driven models to estimate CWSI reference temperatures, correlate CWSI with malt barely seed yield and quality measures and use the results to assess applicability of CWSI for malt barley irrigation scheduling in a semi-arid climate. The three-year field study used five irrigation rates: full irrigation (FIT), 75, 50 and 25% of FIT and no irrigation. There were significant differences in daily average CWSI between irrigation treatments. Relative evapotranspiration, relative malt barley seed yield, seed test weight and percent plump kernels were negatively correlated with season average CWSI. Malt barley seed protein 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 CWSI to irrigated spring malt barley in a semi-arid environment and demonstrate malt barley yield response to thermal crop water stress.

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°C and mean absolute error 0.70°C. There were significant differences in calculated daily average CWSI between irrigation treatments. Relative evapotranspiration, relative malt barley seed yield, seed test weight and percent plump kernels were negatively correlated with season average CWSI. Malt barley seed protein 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.