Yield and water use of guayule grown in Arizona

Abstract

<abstract> <bold>Abstract.</bold> Guayule (Parthenium argentatum) is being produced for high-quality, domestic rubber in Arizona, U.S.A, desert areas, where irrigation requirements are high. Past guayule irrigation research was mostly conducted over two to three decades ago and provided some insight on irrigation water management for rubber production. However, improved irrigation management practices are now needed to increase guayule yield productivity and reduce its water use. In 2012, irrigation field experiments were initiated in Maricopa, Arizona using a guayule cultivar (Yulex-B), currently under production in the area. The objectives are to advance understanding of biomass and rubber yield responses to irrigation method, water application, and soil water status. The experiments are being conducted with subsurface drip irrigation (SDI) and blocked-furrow irrigation in Maricopa, Arizona, on two nearby 1.4-ha fields. Guayule seedlings were transplanted in both fields in October, 2012, at a 0.35-m spacing, along 100-m rows, with row spacing of 1.02 m. Each field consists of 15 plots (5 treatments x 3 replicates). Each plot consists of 8 and 5 rows in the SDI and furrow-irrigated fields, respectively. In the spring of 2013, 5 irrigation treatments were imposed on plots in a randomized complete block design. Irrigation treatment levels replaced 25%, 50%, 75%, 100% and 125% of estimated crop evapotranspiration (ET) for the SDI field and 40%, 60%, 80%, 100% and 120% of estimated ET for the surface irrigated field. The crop ET replacements for all treatments were based on that determined for the 100% treatment from soil water balance calculations using soil water content, irrigation, and rainfall measurements. The fields were irrigated when ≈65% and ≈35% of available soil water of the root zone remained for the 100% ET treatments for the SDI and surface fields, respectively. The final harvest of fields are planned to occur in the fall of 2014, two years after transplanting. However, pre-final-harvest destructive samplings of plants were made in each plot in between July and November, 2013. Measurements of the samples included canopy heights and widths, fresh and dry biomass weights, and rubber and resin contents. Experimental results for the first year of guayule growth indicate increased biomass, dry matter, plant height, and canopy cover with irrigation water amount for both irrigation methods. The relationships obtained between rubber yield and water applied are presented.