EFFECTS OF HEIGHT AND FREQUENCY OF CUTTING ON YIELD, QUALITY AND PERSISTENCE OF DESMANTHUS-VIRGATUS

Desmanthus virgatus has demonstrated potential as a pasture legume, pa rticularly on tropical and subtropical clay soils that are neutral to alkaline. To increase understanding of its responses to defoliation, a factorial combination of 5, 25 and 100-cm stubble heights and 2, 4 an d 12-week harvest intervals was imposed on field plots of D. virgatus accession IRFL 1857 over 2 years. Leaf and stem yield, in vitro digest ibility, crude protein and number of growing points following defoliat ion were determined. Total non-structural carbohydrate (TNC) concentra tions in roots and stems were also measured following each of 2 growin g seasons of defoliation. Both total dry matter harvested and leaf yie ld were greatest when plants were harvested every 2 weeks at a stubble height of 100 cm. TNC levels were highest and leaf digestibility was among the lowest in 1990 with this treatment combination. Close and fr equent harvesting resulted in low yields, low TNC concentrations, very few shoots, and stand loss following 1 year of defoliation. These res ults indicate that frequent but light defoliation will maximise produc tivity. However, leaf digestibility can be lower under such utilisatio n, perhaps due to high tannin levels. No plants survived into the four th year.