GRAIN-YIELD PREDICTION - EXTENDING THE STRESS-DEGREE-DAY APPROACH TO ACCOMMODATE CLIMATIC VARIABILITY

Combination of the stress-degree-day concept of plant water stress assessment with the growing degree-day concept of plant phenological development leads to a new approach to the prediction of grain crop yields that accounts for climatic effects of light, temperature, and water. The model requires knowledge of the dates of plant emergence and heading, maximum and minimum air temperatures through the growing season, and midafternoon canopy-air temperature differentials from the time of heading to physiological maturity. Its utility is illustrated by development of the predictive relationship for a specific cultivar of wheat grown at Phoenix, Arizona, and a test of its predictions for the same cultivar grown at Davis, California. Both final yield and the time of cessation of crop growth are adequately predicted. © 1979.