Harvest Height Effects On Yields of Five Guayule Lines.

Guayule (Parthenium argentatum Gray) is a perennial shrub native to the Chihuahuan Desert. The commercialization of guayule for hypoallergenic latex and other products has renewed interest in production practices such as harvesting height and frequency. The objectives of this study were to determine yield and concentration of latex, rubber, and resin of five guayule lines harvested at two cutting heights over three years and four harvesting schedules. The five lines with variable plant height used were AZ-2, AZ101, AZ-1, 11591, and N9-3 (tallest to shortest). Each treatment was replicated four times. Yields were compared for each of the three harvest years and for total production across all four years. Harvesting at 100% of plant height gave higher yields than harvesting at 50% of plant height independent of the harvest schedule. Harvesting at 100% after four years of growth gave the highest yields, but more research is needed to determine if harvesting on a two year schedule may be easier for harvesting and extraction equipment. We did notice some plants did not regrow well when cut at 100% for three years consecutively. AZ-2 and AZ101 were the largest plants, while N9-3 and 11591 were smaller with AZ-1 intermediate. The results for these lines were similar to previous studies when they were harvested at 100% of plant growth. There were significant interactions among lines and treatments. However, the interaction effects were smaller than the main effects of line and harvest schedule treatment due mainly to the much smaller plant size of N9-3 compared to the other liens. As indicated in previous studies, the environment plays a large role in determining biomass, latex, rubber, and resin yields in guayule. In the future, optimum harvesting schemes at 100% of plant height may need to be developed for each line and environment.