ABSTRACT

The study on the stabilizing effect of Bambusa vulgaris , Vernonia amygdalina and Vetiveria zizanioides on some developing guiiy slopes was carried out in Abia State, Nigeria. The aim was to determine whether the selected plants could combine with the naturally —growing vegetation to prevent the slopes from further destabilization. Three farming communities were systematically selected for the study and included Azuiyi Oloko (Site 1) in Ikwuano Local Government Area and Ebem Ogugu and Ogboko Road (Sites 2 and 3) respectively ,both in Bende Local Government Area. In each site, developing gully slopes averaging 450,600 and 750 in steepness were measured and marked out within 100 sq.m. (0.Olha) on both sides of the slope. These were planted with Bambusa vulgaris, Vernonia amygdalina And Vetiveria zizanioides, one meter apart, in three planting densities. An equivalent site was measured, adjacent to the planted plot and left as control. Soil tests were conducted at two depths to ascertain the condition of the soil, on planting and four years later. Studies were also done on gully floor sedimentation rates, and on the ability of the plants used for erosion control to survive and to produce stems, roots and tillers .The investigation also involved enumeration of common flora in each site. The research was done with a 3 x 3x 3x3 factorial based randomized complete block design. The factors were site, slope,species and density. Results vi' showed that four years after planting ,Barnbusa vulgaris had stabilized the slopes more than Vetiveria zizanioides and Vrnonia amygdalina, irrespective of the planting density adopted. Following B. vugaris in stabilizing capacity was V. zizanioides. Steeper slopes exhibited more severe erosion. Slope erosion was most severe in the control plots. The length of the roots of the planted species played an important role in interlocking and holding the soil together. Also the survival rates of the three plants used and their ability to reproduce stems and tillers were high, and gully floors were found to retain more sediments as the plants grew and established. Soil conditions were found to be favourable for the survival and growth of both the planted species and the naturally-growing vegetation, even four years later. However, the pH levels of Azuiyi Oloko (Sitel) and Ebem Ogugu (Site 2) needed to be raised by at least 1.0. Recommendations included the adoption of the Rural Participatory Approach, where farmers would be incorporated into soil erosion control efforts. Enlightenment, training and adequate compensations could help in realizing this. Governments should encourage Agroforestry, which enhances both ecological and economic interactions between the trees and other ecosystem components above and below ground, and transfers of biomass by the addition of litter and pruning to the soil. It would also be appropriate to plant more of B. vulgaris on the gully floors to trap more sediments. These could go a long way VIII to help de-emphasize some unnecessary engineering approaches to soil erosion control, which are very capital intensive and, in some cases, environmentally unfriendly.