Allelopathic effects of bankrupt bush (Seriphium plumosum) on the germination ability of specific plant species

Abstract

Seriphium plumosum is a declared indicator of bush encroachment, and poses a serious threat to the management of sustainable utilization in all grasslands. The successful invasiveness of S. plumosum is attributed to its competitive ability and high allelopathic potential. A trial was established at the University of Limpopo to investigate the interference between S. plumosum and four plant species, namely: Eragrostis curvula, E. tef, Panicum maximum and Lactuca sativa. Plant material of S. plumosum were collected and used to make infusions which were used on the receiver species. The infusion inhibited the germination of all the receiver species, and it was highly significant (P ≤ 0.01), compared to control treatments where no inhibition occurred. All receiver species were sensitive to roots and shoots infusions, but the effect of shoots infusion differed significantly (P ≤ 0.01) from those of roots infusion. All receiver species were sensitive to both summer and winter collected materials, but plant material collected in winter had a bigger effect (P ≤ 0.01) than plant material from summer. All receiver species were sensitive to both fresh and stored plant material, but inhibition effects were not statistically significantly different (P ≥ 0.05). All receiver species were sensitive to both fresh and stored soils collected in infested areas, but effects were not significantly different (P ≥ 0.05), while the effects of infested and un-infested soils differed significantly (P ≤ 0.01). All receiver species were sensitive to soils collected during summer and winter. Where infested soils were concerned, all receiver species were sensitive to infested soils, compared to control treatments where no effects occurred. Where stored infested soils were concerned, all receiver species were sensitive to both fresh and stored infested soils. It was concluded that both plant material of S. plumosum and soils from areas encroached by S. plumosum have a negative effect on seed germination of the four receiver species. Should a farmer control this species by means of cutting, it should be quickly removed to allow the gass to recover. The farmer must not expect quick recovery of grasses due to the presence of allelopathic substances in the soil.