Evaluation of Potential Allelopathic Relationship between Velvet bean (Mucuna cochinchinensis (Lour.) A. Chevand Speargrass (Imperata cylindrical (L.) Raeushel) with Selected Methods

Abstract

Velvet bean [Mucuna cochinchinensis (Lour.) A. Chev] has been reported to smother the growth of Speargrass [Imperata cylindrical (L) Raeushel.] through competition and potential allelopathic effect on speargrass. Greenhouse experiments involving three methods were conducted at International Institute of Tropical Agriculture (IITA), Ibadan Nigeria in 2009. The aim of the trials was to establish if mucuna exhibits allelopathic effect on speargrass, besides smothering effect. These methods included: (1) Mucuna fresh parts[(Leaves (L), leaves + vine (L+V), vine(V) and roots (R)] incorporation into pot planted to speargrass rhizome and a control pot without mucuna part incorporation; (2) Mucuna plant part extracts (of leaves, leaves +vines, vines and roots) and control with ordinary water; and (3) Mucuna seed and speargrass rhizome interplant (One mucuna seed-interplant, Two mucuna seeds interplant and Three-mucuna seeds interplant). Results showed that every mucuna part has the potentials of being allelopathic to speargrass. Incorporating mucuna parts into pot with speargrass reduced both speargrass shoot height and number by ≥ 20% and ≥ 50% respectively. Similarly mucuna parts extract on the average, reduced shoot and rhizome biomass by ≥ 60% and ≥ 50% respectively when compared to the control. The pot interplant method on the average showed a reduction of speargrass shoot and rhizome biomass by ≥ 20% and ≥ 16% respectively. The effect of speargrass and mucuna interplant on speargrass shoot height was not variable between the speargrass-mucuna interplant and the sole speargrass control except at 12 WAP. This investigation revealed that mucuna also exhibits allelopathic effect on speargrass, and this could serve as a bio-control method for speargrass. All the mucuna parts studied have the potentials of exhibiting allelopathy effect on neighboring and susceptible plants. The allelopathy effect appears to be greater with the leaves or the vines or both.