Context: Introducing legumes into grass-based forage systems may increase herbage nutritive value while reducing the need for inorganic nitrogen fertilisation. Grass–legume intercrops may also enhance herbage yield stability.

Aim: We evaluated agronomic and nutritional traits of elephant grass (Cenchrus purpureus Schum.) genotypes grown as monocrops and mixed with butterfly pea (Clitoria ternatea L.).

Methods: Elephant grass genotypes, two tall (Elephant B and IRI-381) and two dwarf (Mott and Taiwan A-146 2.37), were grown as monocultures or intercropped with butterfly pea in a 2-year trial. Herbage accumulation, yield stability, botanical composition and chemical/bromatological variables were evaluated.

Key results: Herbage accumulation was highest (P < 0.001) in Elephant B under monocropping (21.9 t/ha.year); however, this treatment revealed the lowest yield stability over harvest times (σ_i² 5.59). All intercrops were more stable than grass monocrops (mean σ_i² 0.66 vs 2.55). Higher (P < 0.001) concentrations of herbage crude protein were found in intercrops than monocrops (mean 113 vs 90 g/kg). Intercrop herbage lignin contents (mean 57 g/kg) and protein fraction C (mean 61 g/kg) were higher than those in monocrops. Dwarf Mott had higher (P = 0.001) digestible dry matter concentration than dwarf Taiwan (755 vs 745 g/kg).

Conclusions: Dwarf Mott genotype has outstanding nutritive value because of its higher leaf:stem ratio. Butterfly pea legume added to elephant grass crop in cut-and-carry systems improves herbage yield stability by reducing seasonal effects.

Implications: Intercropping butterfly pea in grass-based systems enhances yield stability, allowing herbage harvest with good nutritive value.