Ozone Dosage-Crop Loss Function for Alfalfa: A Standardized Method for Assessing Crop Losses from Air Pollutants

Ozone dose-crop loss conversion functions for alfalfa (Medicago sativa, L. var. Moapa 69) yield reduction and defoliation were developed using standardized field plots within an ambient O₃ gradient in the South Coast Air Basin. Seasonal yields and defoliation values were tested with O₃ dose, average daily maximum temperature, average daily minimum temperature, and average daily relative humidity in regression analyses to determine significant functional relationships. Only the ambient O₃ dose variable was found to have a significant effect on alfalfa yield or defoliation (yield, r = –0.827, t-slope = 3.900**; defoliation, r = –0.890, t-slope = 5.190**). The ozone dose-crop loss conversion functions were calculated by converting the dose-response functions to dose-percent reduction functions.