Performance of direct-seeded and transplanted guayule

Abstract

The commercialization of guayule ( Parthenium argentatum, Gray) depends on economical plant production. Direct seeding has been successful and can reduce establishment costs when compared with seedling transplanting. Most economic and yield analyses have been based on transplants. The performance of direct-seeded and transplanted shrubs grown under the same field conditions has never been compared. The objective of this study was to evaluate various production parameters (biomass, rubber and resin content, rubber and resin yield) of five guayule lines established by direct seeding and transplanting. An experiment was initiated on a Delnorte very gravelly loam on 17 and 18 May 1994 at the Texas Agricultural Experiment Station near Fort Stockton, TX. Guayule selections AZ-R2, AZ-R3, 11 605, CAL-6, and UC-101 were direct-seeded and transplanted on raised beds spaced 1 m apart. Six plants from each line/replication were harvested on 6 March 1996 and 11 March 1997. Each plant was divided into branch (clipped 10 cm above the soil surface) and root (10 cm of lower branches plus approximately 15 cm of roots) sections. Guayule branch biomass was greater than root biomass at both harvests. Direct-seeded branch, root and total biomass was significantly lower than transplanted biomass in 1996. After 34 months at the 1997 harvest, no significant differences were observed between direct-seeded and transplanted shrubs. Resin and rubber content (%), and resin and rubber yield (kg/ha) were significantly greater in transplants versus direct-seeded shrubs in 1996, but not in 1997. Thus, direct seeding would be a viable system for commercially establishing guayule stands. Line AZ-R3 exhibited the least potential of the five lines to overcome the initial growth advantage of the transplants. Lines AZ-R2, 11 605, and CAL-6 are recommended for cultivation in west Texas and southern New Mexico.