Utilization of the Neighborhood Design to Evaluate Suitable Pasture Crops and Their Density for Navua Sedge (Cyperus aromaticus) Management

Abstract

Navua sedge (Cyperus aromaticus), a perennial plant native to Africa, poses a significant weed concern due to its capacity for seed and rhizome fragment dissemination. Infestations can diminish pasture carrying capacity, displacing desirable species. Despite the burgeoning interest in integrated weed management strategies, information regarding the efficacy of competitive interactions with other pasture species for Navua sedge management remains limited. A pot trial investigated the competitive abilities of 14 diverse broadleaf and grass pasture species. The results indicated a range of the reduction in Navua sedge dry biomass from 6% to 98% across these species. Subsequently, three broadleaf species—burgundy bean (Macroptilium bracteatum), cowpea (Vigna unguiculata), and lablab (Lablab purpureus), and three grass species—Gatton panic (Megathyrsus maximus), Rhodes grass (Chloris gayana), and signal grass (Urochloa decumbens) were chosen for a follow-up pot trial based on their superior dry biomass performance. These six species were planted at three varying densities (44, 88, and 176 plants/m2) surrounding a Navua sedge plant. Among the grass pasture species, Gatton panic and Rhodes grass exhibited high competitiveness, resulting in a minimum decrease of 86% and 99%, respectively, in Navua sedge dry biomass. Regarding the broadleaf species, lablab displayed the highest competitiveness, causing a minimum decrease of 99% in Navua sedge dry biomass. This study highlights the increasing efficacy of crop competition in suppressing weed growth and seed production, with the most significant suppression observed at a density of 176 plants/m2.