Survival and growth analysis of multipurpose trees, shrubs, and grasses used to rehabilitate badlands in the subhumid tropics.
Vegetation plays a vital role for sustainable rehabilitation of degraded lands such as badlands with active gully erosion. However, the establishment of plant species on badlands remains a long-lasting challenge in most regions, including the subhumid tropics. To address this challenge, 18 multipurpose plant species (six trees, three shrubs, and nine grasses), which were preselected from the regional species pool in Southwest Ethiopia, were planted in a badland and monitored from July 2011 to June 2014. The experiment had a split-plot design with farmyard manure (FYM) application as main plot and plant species as subplot factors repeated in three blocks. The study revealed that grasses were the most successful to survive and rehabilitate the gully within the monitoring period compared with trees and shrubs. The survival rate of the four most successful grass species, Chrysopogon zizanioides, Pennisetum macrourum, Pennisetum polystachion, and Pennisetum purpureum ranged from 61% to 90% with FYM application and from 20% to 85% without FYM, while most of the well-known indigenous and exotic trees and shrubs failed to survive. For the grass P. purpureum, shoot height, shoot, and root biomass were enhanced by 300%, 342%, and 578%, respectively, due to FYM application, with a remarkably higher response to FYM compared with all the other studied species. The overall results demonstrate that badlands can be effectively restored by using early successional species such as locally adapted and selected grasses before the plantation of trees and shrubs.