Hierarchical ranking of Urochloa mosambicensis (Bushveld herringbone grass) and Urochloa panicoides (Herringbone grass) competitiveness in four soil environments

Abstract

Knowledge of the competitive ability of weeds provide a better understanding of the requirements for weed control. The competitive ability of Urochloa mosambicensis (Hack.) Dandy. (Bushveld herringbone grass) and U. panicoides P. Beauv. (Herringbone grass) was investigated during 2017/18 in four soil environments under glasshouse conditions: (1) 16% clay, dry; (2) 16% clay, wet; (3) 35% clay, dry; and (4) 35% clay, wet. The two grass species were planted in five treatment combinations at proportions of 100:0, 75:25, 50:50, 25:75 and 0:100. Root and shoot biomass were used to calculate competitive indices (aggressivity [A] and competitive ratio [CR]) and root:shoot ratios. Urochloa mosambicensis generally competed best in 16% clay soil, whilst U. panicoides preferred the 35% clay soil. Urochloa mosambicensis demonstrated greater plasticity than U. panicoides by adjusting root:shoot ratios in changing environments in the 35% clay soils, which suggested U. mosambicensis to be the more successful species.