Response of guayule biomass and rubber yield to variable water inputs using subsurface drip irrigation

Abstract.

Abstract. Guayule (Parthenium argentatum) is being produced for natural rubber in Arizona, U.S.A, desert areas, where irrigation requirements are high. Improved irrigation management practices are required to increase guayule yield productivity and reduce its water use. A subsurface drip irrigation (SDI) field experiment was initiated in 2012 in Maricopa, Arizona using a guayule cultivar (Yulex-B). The objective was to increase understanding of guayule biomass and rubber yield response to water application rate and soil water status under SDI. The experiment was conducted in Maricopa Agricultural Center (MAC), Maricopa, Arizona, USA. Guayule seedlings (≈95 day old) were transplanted in the field in October, 2012, at a 0.35-m spacing, along 100-m rows, with row spacing of 1.02 m. The field consisted of 15 plots (5 treatments x 3 replicates), 8 rows each. In the spring of 2013, 5 irrigation treatments were imposed on plots in a randomized complete block design. Irrigation treatment levels were 25%, 50%, 75%, 100% and 125% of irrigation applied to the 100% treatment, based on measured soil water depletion (SWD). The field was irrigated when SWD reached 30-35% for the 100% treatment using soil water content measurements applied in a soil water balance model. Pre-final harvest destructive samples were taken from each plot in between April and November of each year until the guayule was harvested in March 2015. Results indicated increased dry biomass, rubber yield, plant height and percent cover with irrigation water amount, which varied from 860 to 2030 mm annually for treatments. Final biomass and rubber yield of 61.2 Mg/ha and 3430 kg/ha, respectively, was achieved with the highest irrigation treatment level (125%) and these were significantly higher than those under all other irrigation levels.