Vetiver forage yield and nutritive value affected by water irrigation regimes and plant density under Mediterranean climate conditions

Climate change constitutes a threat for the sustainability of fodder crops production. With the aim of introducing vetiver grass as a resilient forage alternative in the Mediterranean basin, a field trial was set up at three-consecutive-year field experiments (2015, 2016, and 2017) in the North of Tunisia. The effects of irrigation regimes and planting density on the growth parameters, fodder yield, and quality of vetiver grass (Chrysopogon zizanioides L.) ‘Sunshine’ were assessed. The experiment was arranged in a split-plot factorial design with four irrigation regimes: optimum (Ir75), moderate (Ir100), severe (Ir125) and very severe (Ir150) combined with three plant densities (D1: 10,000, D2: 20,000 and D3: 40,000 plants ha−1). The findings showed that a short (Ir75) and moderate (Ir100) irrigation intervals improved production mainly influenced by the number of tillers. Additionally, the medium (D2) and the highest (D3) densities gave the best results in terms of DMY (14.7 and 14.6 T ha−1) and PY (1638.3 and 1540.3 kg ha−1) for all water regimes. Multiple linear regression analysis revealed that PY was explained by the DMY and crude protein content under Ir × D interaction. The optimal combination for maximizing PY (1978.46 kg ha−1) appears to be the result of the interaction between a moderate irrigation regime (Ir100) and average plant density (20,000 plants ha−1).These results highlight that the vetiver’s grass potential to cope with water scarcity conditions by enhancing the DMY and PY, might be provided by the use of a specific planting density and irrigation dose.