Guayule biomass and rubber yield under variable water inputs using surface irrigation

Abstract. Interest in agricultural production of guayule (Parthenium argentatum G.) in Southwestern USA deserts is spurred by a goal of attaining a domestic natural rubber supply. Limited and dated information on guayule irrigation management exists but advanced knowledge is needed for today‘s growers. In this paper, guayule growth, rubber, yield, and crop evapotranspiration (ETc) responses to irrigation were evaluated for a present-day cultivar, Yulex-B, during a 29-month surface irrigation study in Maricopa, Arizona USA. Seedlings were transplanted within a 1.4-ha field in October 2012, at 0.36-m spacing, along 1.02-m by 100-m rows. Five irrigation treatments were imposed in three block replicates from April 2013 through 2015, prior to final harvest in March 2015. Treatment irrigation amounts were 40, 60, 80, 100, and 120% of irrigation applied to the 100% treatment, based on measured soil water depletion (SWD) for the 100%. Measured SWD percentage prior to irrigation for the 100% averaged 59%. The total water applied (TWA), including rain, from transplanting to final harvest, varied from 2370 to 4720 mm. Cumulative ETc measured from April 2013 through March 2015 varied from 1750 to 3660 mm. At final harvest, dry biomass (DB) varied from 15,700 to 27,900 kg/ha and rubber yield (RY) from 1220 to 1680 kg/ha. The study confirms that both DB and RY respond linearly to irrigation input, thus, maximizing DB maximizes rubber yield. For maximum rubber yield using surface irrigation, it is recommended to use SWD of 50% for irrigation scheduling and apply ≈1950 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 application achieved 92% of the maximum RY in the study.