Guayule growth and yield responses to deficit irrigation strategies in the U.S. desert

Authors: ELSHIKHA, DIAA ELDIN - University Of Arizona; WANG, GUANGYAO - Bridgestone Americas Tire Operations; WALLER, PETER - University Of Arizona; Hunsaker, Douglas - Doug; DIERIG, DAVID - Bridgestone Americas Tire Operations; Thorp, Kelly; Thompson, Alison; KATTERMAN, MATTHEW - University Of Arizona; Herritt, Matthew; Bautista, Eduardo; RAY, DENNIS - University Of Arizona; Wall, Gerard - Gary

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2022
Publication Date: 12/12/2022
Citation: Elshikha, D.M., Wang, G., Waller, P.M., Hunsaker, D.J., Dierig, D., Thorp, K.R., Thompson, A.L., Katterman, M.E., Herritt, M.T., Bautista, E., Ray, D.T., Wall, G.W. 2022. Guayule growth and yield responses to deficit irrigation strategies in the U.S. desert. Agricultural Water Management. 277. Article 108093. https://doi.org/10.1016/j.agwat.2022.108093.
DOI: https://doi.org/10.1016/j.agwat.2022.108093

Interpretive Summary: Guayule is a perennial shrub native to the Chihuahuan Desert that produces high quality natural rubber, appropriate for manufacturing commercial-grade tires. US tire companies and others seek to commercialize guayule in the US Southwest to provide domestic supplies of this natural rubber. However, severe water shortages in the region require guayule deficit irrigation strategies that can maintain rubber yields, while also greatly reducing irrigation water use. In this field experiment, research conducted by ARS scientists in Maricopa, Arizona, explored a number of different deficit irrigation strategies to see if such approaches could attain high rubber yields comparable to a fully-irrigated treatment. The research found that guayule plant size increased at the full irrigation amount, however, the rubber content in plants generally increased in deficit irrigation treatments. Notably, one particular deficit irrigation strategy was able to attain a rubber yield like that of the fully-irrigated treatment and reduce irrigation amount by 36%. The research provides new knowledge on guayule deficit irrigation management to sustain yields with significant water savings. The research will be of interest to the US Rubber Industry, including Tire Manufacturers, irrigation consultants, water district water managers, and other research investigators of guayule.

Technical Abstract: Deficit irrigation can maximize the water productivity (WP) of guayule and increase the percent rubber (%R) in shrubs compared to irrigation meeting full crop evapotranspiration (ETc). In this study, we hypothesize that certain deficit irrigation strategies that impose soil water deficits during specific periods of growth or throughout the growing season might produce higher %R and equivalent rubber yield (RY), thereby, increasing WP compared to full irrigation. Herein, growth and yield responses of direct-seeded guayule to different water deficit schemes were evaluated in an experiment on a 1.6-ha field in Arizona using furrow irrigation. Two guayule cultivars (AZ2 and AZ6) were grown for 22.5 months (Apr. 2020-Mar. 2022) in a split-plot design, with six irrigation treatments in whole plots and cultivars in split-plots. After homogeneous irrigation for two months, irrigation treatments were begun as follows: I1, irrigation meeting full ETc (control); I2, same as I1, then imposed deficit seven months before harvest; I3, same as I1, then imposed deficit during the second-year summer; I4, every other I1 irrigation; I5 and I6, two and one irrigations in the first and second years, respectively. Measurements included plant height (h), cover fraction (fc), soil water contents, and harvest of dry biomass (DB), RY, resin yield (ReY), %R, and percent resin (%Re). Total water applied by irrigation and precipitation varied from 2780 to 1084 mm and DB varied from 20.5 to 9.1 Mg ha-1 for I1 and I6, respectively. The h and fc were significantly greater at higher irrigation levels, while they were significantly greater in AZ6 than AZ2. The DB, RY, and ReY were not significantly different among the I1, I2, and I4 treatments, whereas they were significantly lower than I1 for I3, I5, and I6. The %R generally decreased with irrigation, while %Re was not affected by irrigation. However, DB, %R, and %Re were significantly greater for AZ2 than AZ6, as were RY, ReY, and WP. Among deficit strategies, every other irrigation (I4) offers the best strategy to significantly increase guayule WP without causing a yield penalty.