Irrigation effects on seasonal growth and rubber production of direct-seeded guayule

Authors: WANG, GUANGYAO - Bridgestone Americas Tire Operations; ELSHIKHA, DIAA ELDIN - University Of Arizona; KATTERMAN, MATTHEW - University Of Arizona; SULLIVAN, THERESA - Bridgestone Americas Tire Operations; DITTMAR, STEFAN - Bridgestone Americas Tire Operations; CRUZ, V - Bridgestone Americas Tire Operations; Hunsaker, Douglas - Doug; WALLER, PETER - University Of Arizona; RAY, DENNIS - University Of Arizona; DIERIG, DAVID - Bridgestone Americas Tire Operations

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2021
Publication Date: 12/30/2021
Citation: Wang, G., Elshikha, D.M., Katterman, M.E., Sullivan, T., Dittmar, S., Cruz, V.M., Hunsaker, D.J., Waller, P.M., Ray, D.T., Dierig, D.A. 2021. Irrigation effects on seasonal growth and rubber production of direct-seeded guayule. Industrial Crops and Products. 177. Article 114442. https://doi.org/10.1016/j.indcrop.2021.114442.
DOI: https://doi.org/10.1016/j.indcrop.2021.114442

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. Obtaining profitable and sustainable guayule in this region requires understanding of guayule growth responses to irrigation. A critical goal is developing irrigation strategies that maximize plant rubber accumulation throughout the two-year growing period. To meet this goal, irrigation studies of direct-seeded guayule in Arizona were conducted on two different soil types by ARS scientists in Maricopa, Arizona. The research found that reducing irrigation decreased guayule biomass yield, but also significantly increased the plant’s rubber content. It was shown that rubber yield increased linearly with time, indicating that rubber is accumulated year-round. A major finding was that irrigation water amount can be reduced by half the recommended rate on a clay soil without a significant reduction in rubber yield. 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: Understanding guayule’s response to environmental factors, such as location, soil type, drought stress, and seasonal growth variation is critical for irrigation management to maximize and estimate rubber and resin accumulation throughout the growing seasons. A study was conducted at two sites with different soil types (sandy loam soil at Maricopa, AZ and a clay soil at Eloy, AZ) to compare plant growth and rubber accumulation among different irrigation treatments during a two-year growing season. The above- and below-ground biomass, biomass growth, rubber/resin content, and rubber/resin accumulation were measured every other month from establishment to final harvest in well-watered treatments, which received 100% replacement of crop evapotranspiration (ETc) and irrigated with subsurface drip and furrow (denoted as D100 and F100, respectively), and compared to reduced irrigation treatments (D50 and F50), which received 50% replacement of ETc. Drip irrigation with high water input (D100) decreased root mass partition, but leaf, stem, and flower partitions were not significantly affected by irrigation treatment. Biomass yield was higher in the well-watered treatments as expected, while rubber and resin content were lower, indicating rubber and resin dilution by higher biomass. For all treatments, rubber and resin yield increased linearly over the two-year growing season. However, the rates of increase were different among the irrigation treatments. The D100 treatment had a higher rubber yield increase rate compared to F100 and D50 in sandy loam soil at Maricopa, while the D100 treatment had the lowest increase rate compared to the F100, F50, and D50 treatments in clay soil at Eloy. Top branches of guayule plants in the D100 treatment at Eloy lodged in the second year and likely contributed to lower rubber content and rubber yield in the treatment. The drip irrigation treatments D50 and D100 had higher water productivity for rubber yield at Maricopa. However, the D50 and F50 treatment had the highest water productivity for guayule rubber yield, while the D100 treatment had the lowest due to low rubber content at Eloy. Root rubber content was 31% to 39% lower than stem at the two locations. This study indicates that rubber biosynthesis occurred in guayule year-round and that it is possible in clay soils to reduce irrigation without a significant loss in rubber yield.