Growth, water use, and crop coefficients of direct-seeded guayule with furrow and subsurface drip irrigation in Arizona

Authors: ELSHIKHA, DIAA ELDIN - University Of Arizona; WALLER, PETER - University Of Arizona; Hunsaker, Douglas - Doug; DIERIG, DAVID - Bridgestone Americas Tire Operations, Llc; WANG, SAM - Bridgestone Americas Tire Operations, Llc; CRUZ, VON MARK - Bridgestone Americas Tire Operations, Llc; Thorp, Kelly; KATTERMAN, MATTHEW - University Of Arizona; Bronson, Kevin; Wall, Gerard - Gary

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2021
Publication Date: 7/14/2021
Citation: Elshikha, D.M., Waller, P.M., Hunsaker, D.J., Dierig, D., Wang, S., Cruz, V.V., Thorp, K.R., Katterman, M.E., Bronson, K.F., Wall, G.W. 2021. Growth, water use, and crop coefficients of direct-seeded guayule with furrow and subsurface drip irrigation in Arizona. Industrial Crops and Products. 170. Article 113819. https://doi.org/10.1016/j.indcrop.2021.113819.
DOI: https://doi.org/10.1016/j.indcrop.2021.113819

Interpretive Summary: In recent years, US tire companies and others have increased efforts to develop and commercialize guayule in the arid US Southwest for domestic supplies of natural rubber. A critical matter in making guayule both profitable and sustainable in this region is ability to grow guayule by directly seeding it in the soil because costs of transplanting guayule are about ten times more than direct seeded. Since no information is currently available on irrigation management of direct-seeded guayule, irrigation research was conducted by ARS scientists in Maricopa, Arizona. The research found that guayule rubber yield generally increased with higher irrigation water use in soils that are sandy but decreased with higher irrigation in clay soils. The studies provide recommended irrigation management practices for direct-seeded guayule for both sandy and clay soils. The research will also 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: Guayule (Parthenium argentatum A. Gray) commercialization depends on economical plant production. Crop establishment costs can be reduced significantly with direct seeding compared to the traditional method of transplanting seedlings. However, current soil and water management strategies for guayule are almost entirely based on transplants using furrow irrigation. Since direct-seeded and transplanted guayule plants may develop different root architecture, they likely will differ in crop water use requirements and soil water management. The objectives of these studies were to evaluate the growth and yield responses (biomass, rubber, and resin) of direct-seeded guayule to water application rate and to formulate optimum irrigation management criteria for two different soil types. Field studies were conducted using five irrigation rates applied with subsurface drip irrigation (SDI) in 25% increments ranging from 50 to 150% replacement of crop evapotranspiration (ETc) denoted as the D50 to D150 treatments, respectively. One additional treatment in the study used furrow irrigation at 100% ETc replacement, denoted as F100. ETc was calculated using soil water content measurements applied in a root zone soil water balance. The experiment was replicated in two fields at the: (1) Maricopa Agricultural Center, Maricopa, Arizona on a sandy loam soil and; (2) Bridgestone Americas Guayule Research Farm, Eloy, Arizona on a clay soil. The experiment was planted in Apr. 2018 at each location. Guayule variety AZ-2 was direct-seeded in a single row on raised beds spaced 1.02 m apart. After planting, plots were sprinkler-irrigated daily for two weeks at both fields. Then, all plots received equal amounts of irrigation water for the next three months until irrigation treatments were initiated in late-July (Maricopa) and early-Aug. (Eloy). Plants were harvested for yield in early Mar. and mid-Apr. 2020 at Maricopa and Eloy (˜23 and 24 months after planting), respectively. The total irrigation applied to treatments at harvest ranged from 1830-1910 mm for D50 to 5090-5470 for D150 and averaged 3560 and 3310 mm for the 100% treatments (D100 and F100) at Maricopa and Eloy, respectively. Location average biomass for direct-seeded guayule at Eloy (28.6 Mg ha-1) was higher than at Maricopa (24.0 Mg ha-1) but average rubber and resin contents, and rubber and resin yields were all significantly higher at Maricopa. At each location, rubber content was significantly higher for the F100 and the two lowest SDI rates (D50 and D75) than in other treatments. The highest mean rubber yield and resin yield at Maricopa (sandy loam) and Eloy (clay) were achieved by the D100 and D75 treatments, respectively. In addition, these two treatments had significantly greater water productivity (WP, yield per unit total water applied) than those at higher SDI rates and the F100 treatments. Irrigating direct-seeded guayule using SDI with rates above D100 (in sandy loam) and D75 (in clay) was not effective in increasing yield and reduced WP. However, water savings may be attained on these soil types by reducing these SDI irrigation rates by 25% and accepting 12-15% lower rubber yields. Yield and WP benefits were seen using SDI rather than furrow at the 100% irrigation rate in the sandy loam but not in the clay soil. Therefore, for direct-seeded guayule in heavier soils with higher water holding capacity, furrow irrigation at 100% estimated ETc may be a reasonable option in terms of increasing yield and WP potential and would eliminate the high costs associated with installing and managing SDI.