Effect of plant density on yield and rubber accumulation in guayule (Parthenium argentatum) in south-eastern Queensland

Abstract

Guayule (Parthenium argentatum) was grown as a rainfed and an irrigated crop on an oxisol in south-eastern Queensland for 36 months, to assess its potential as a source of rubber. The rainfed experiment consisted of 3 cultivars (N565, 11591, 11619) grown at 4 densities (0.9, 1.8, 3.6, 5.2 plants/m2). The irrigated experiment compared cultivars N565 and 11591 at densities of 1.8, 3.6, and 5.2 plants/m2. In both trials, harvests were taken at 4-monthintervals. Dry matter yields of stems and roots, and rubber concentration in stems and roots, showed a near linear increase with time. Stem dry matter yields at 36 months approached 8.0 t/ha, with a rubber concentration of 13%. Rubber concentration and rubber yield increased with plant density. Total rubber yield in stems plus roots after 36 months was about 1.2 t/ha. The low productivity of this crop was associated with poor root development in the soil profile, a low leaf area index, and subsequent low light interception. A main inhibitor to root growth was the high incidence of a Fusarium sp. root pathogen.