Performance of Some Agroforestry Trees in Reclamation of Salt-affected Soils in the Lowlands of Ethiopia

Abstract

To determine the performance of some agroforestry trees in the reclamation of salt-affected soils in the lowlands of Ethiopia, we studied the effects of a series of soils with differing levels of salinity on three indigenous tree species, Balanites aegyptiaca, Tamarindus indica, and Acacia tortilis. We found that salinity had a significant effect on seedling performance. Increasing the soil salt levels caused a significant reduction in the height and in the dry stem and dry root weights of the three species tested. Based on seedling growth parameters, B. aegyptiaca was salt-tolerant even at a high level of salinity (12 dS m−1), while T. indica was moderately salt-tolerant. Salinity had a significant effect on soil compared with control soil in the trees’ response to soil chemical properties. At the seedling stage, B. aegyptiaca and T. indica were found to be the most efficient salt cleansers compared with A. tortilis. Salinity and the interaction between species and salinity level had a significant effect on all seedling growth parameters and soil chemical properties, indicating that salinity was a limiting factor for plant growth. Salinity had a significant effect on the productivity index. A. tortilis and B. aegyptiaca contributed more to soil productivity improvement than T. indica. Further, at the top (0–50 cm) soil depth, the base of the trees had a higher soil productivity index than other soil radii. A. tortilis was found to be the most salt-tolerant and this species showed the most potential for the improvement of soil productivity, followed by B. aegyptiaca and T. indica. Therefore, we suggest that A. tortilis and B. aegyptiaca are suitable for reclamation in arid and semi-arid areas where salinity affects crop development, in both agroforestry systems and strip tree plantings.