Surface irrigation management for guayule rubber production in the US desert Southwest

Agricultural production of the desert shrub, guayule (Parthenium argentatum G.), requires judicious management of irrigation water for achieving economic yields and high water productivity. This study expands existing, but limited and dated knowledge on irrigation management of guayule. A 29-month guayule surface irrigation study (Oct. 2012-Mar. 2015) in Maricopa, Arizona, US, imposed five irrigation treatments whose irrigation amounts were 40, 60, 80, 100, and 120% of irrigation applied to the 100% treatment, based on the soil water depletion (SWD) of the 100%. Irrigation treatments and soil water balance measurements began in Apr. 2013, ≈ 6 mos. after plant establishment. Measured SWD percentage prior to irrigation for the 100% treatment averaged 59%. The total water applied (TWA), irrigation and rain from planting to final harvest, varied from 2370 to 4720 mm. Cumulative ETc measured only over the final 23 months of the study (Apr. 2013 through Mar. 2015) varied from 1740 to 3720 mm. At final harvest, dry biomass (DB) varied from 15.7 to 27.9 Mg/ha, rubber yield (RY) from 1220 to 1680 kg/ha, and resin yield from 1290 to 2720 kg/ha. The study confirms that both DB and RY respond linearly to TWA. For maximum rubber yield using surface irrigation, it is recommended to use a SWD of 50% for irrigation scheduling and apply ≈2000 mm/year of total water. However, guayule water productivity (yield per unit TWA) can be significantly increased by reducing TWA by 25% (i.e., 1460 mm/year). This irrigation rate achieved 92% of the maximum RY in this study.