Assessing the Impacts of Future Climate on Cotton Production in the Arizona Low Desert

Cotton is an important crop in Arizona with a total cash value (cotton seed only) of approximately $32 million in 2018.  In recent years, heat stress from increasing air temperature has reduced cotton productivity in the Arizona low desert (ALD); however, the effects of future climate on ALD cotton production have not been studied. In this study, the DSSAT-CSM CROPGRO-Cotton model was used to simulate the effects of future climate on cotton growth, yield and water use in the ALD area. The projected climate forcings for the ALD were obtained from 9 global climate models under two representative concentration pathways (RCP 4.5 and 8.5).  Cotton growth, yield, and water use were simulated for mid-century (2036 to 2065) and late-century (2066 to 2095) and compared to the baseline (1980 to 2005). Results indicated that seed cotton yield was reduced by at least 40% and 51% by mid-century and late century, respectively, compared to the baseline. Of all the weather variables, the seasonal average maximum (R² = 0.72) and minimum (R² = 0.80) temperatures were most correlated with yield reductions. Under the future climatic condition of the ALD, cotton growth or biomass accumulation slightly increased compared to the baseline. Irrigation requirements in the ALD increased by at least 10% and 14% by mid-century and late-century, respectively. Increases in irrigation requirement were due to an increase in crop water use; hence, higher pressure on freshwater withdrawal for agricultural purposes is anticipated in the future. Therefore, cotton cultivars that are tolerant to long periods of high temperature and improved management practices that promote efficient crop water use are critical for future sustainability of cotton production in the ALD.