Influence of cutting frequency on forage productivity, quality and root growth of vetiver ( <i>Chrysopogon zizanioides</i> (L.) Roberty)

Appropriate harvesting management is critical for ensuring sustainable forage production and enhancing the nutritional quality of forage. This study aimed to determine the optimal cutting interval for maximising both yield and forage quality of vetiver grass (Chrysopogon zizanioides (L.) Roberty) under semi-arid conditions in Tunisia. A field experiment was conducted using four cutting intervals (3, 5, 7 and 9 weeks), and their effects on selected agromorphological and quality parameters were evaluated. Results showed that longer intervals significantly improved fresh and dry biomass yield, with maximum yields recorded at the 9-week interval (11.19 t ha-1 dry matter). Root biomass and depth also increased progressively with longer regrowth periods. Conversely, shorter cutting intervals, particularly at 3 weeks, improved crude protein content, although overall biomass was lower. These findings indicate a trade-off between forage quantity and quality. In conclusion, vetiver grass demonstrates promising potential as a sustainable forage resource in semi-arid regions of Tunisia. However, to optimise its use in ruminant feeding systems, it should be integrated with higher-quality forage species to balance nutritional value.