Does the presence of tall or dwarf elephant grass genotypes change the nutritive value of butterfly pea in grass-legume intercrops?

Adding tropical legumes into grass-based forage systems may increase the nutritive fodder value, but competition may decrease legume quality. We evaluated the nutritional values and agronomic responses of tall and dwarf elephant grass genotypes (Cenchrus purpureus (Schumach.) Morrone.) and butterfly pea (Clitoria ternatea L.) grown as binary intercrops. Two tall (Elephant B and IRI-381) and two dwarf elephant grass genotypes (Mott and Taiwan A-146 2.37) were the grass components of intercrops in a two-year trial. Higher acid detergent fibre (ADF) and lignin contents were found in tall than dwarf elephant grass genotypes (p < 0.0001), while lower coefficients of in vitro digestible dry matter (IVDDM) were recorded in tall than dwarf elephant grass genotypes (p < 0.0001). There was no intercrop effect on the herbage accumulation (p = 0.1278), dry matter (DM) contents (p = 0.2338), neutral detergent fibre (NDF) (p = 0.2022), lignin (p = 0.7179) and condensed tannins (p = 0.1699) of the butterfly pea. The butterfly pea grown with tall genotypes had higher crude protein (CP) concentrations (p = 0.0001) and coefficients of IVDDM (p = 0.0086) than when intercropped with dwarf genotypes. The study showed that tall elephant grass genotypes improved the butterfly pea's nutritional value in grass-legume intercrops through increases in leaf/pod ratio. Intercropping with butterfly pea may compensate for the lower nutritive fodder value of tall elephant grasses compared to dwarf genotypes.