Fall vs. Spring Transplanting of Guayule Germplasm.

Guayule (Parthenium argentatum Gray) is a perennial shrub native to the Chihuahuan Desert. While guayule traditionally has been grown for rubber, more recently it is being grown for its hypoallergenic latex. Other uses such as termite resistant wood products and as an energy source have also been identified. However, the effects of various agronomic practices such as transplanting and harvesting dates, plant spacing, cutting height and frequency, irrigation frequency, and herbicide application, on newly developed germplasm and the effects of these agronomic practices on latex concentration and yield have not been reported. The objectives of this study were to determine the yield and concentration of latex, rubber, and resin of four guayule lines transplanted in the spring and fall. Four guayule lines (AZ-1, AZ-3, AZ-5, and 11591) were transplanted at two dates (28 November 2000 and 7 June 2001) and two plant populations (27,000 and 54,000 plants/ha). Treatments were replicated four times. Each treatment plot was subdivided into six subplots for harvesting at six month intervals beginning one year after transplanting. Results showed that transplanting date did not consistently affect plant size or latex concentration or yield. Instead, it appeared that time of harvest (fall vs. spring) was more important. The last harvest (sixth) in the fall transplanting date and the fifth harvest date in the spring transplanting date were the optimum for plant biomass and latex, rubber, and resin concentrations and yields.