Response of selected indigenous dryland agroforestry tree species to salinity and implications for soil fertility management

摘要

Salt-tolerant plants are known to remove excess soluble salts from the soil and thus may be used in land reclamation. We studied the responses of the trees, Balanites aegyptiaca L. (Zygophyllaceae), as well as the Fabaceae, Acacia tortilis (Forssk) Hayne, and Tamarindus indica L. to salinity. Three experiments were conducted on germination, in the laboratory; seedling performance in a lath house; and the impact of the tree species on soil productivity in the field in Afar regional state along the Awash river, eastern Ethiopia. Mixtures of salts, composed of chlorides and sulfates, were tested at different concentrations in both germination and lath house experiments in randomized complete block designs. Seedling root collar diameter and height were measured every 2 weeks. Soil samples were collected from randomly selected pots to examine the effect of salinity on soil properties. The effects of trees on in situ soil productivity were studied by collecting 72 soil samples at different distances from the tree and different soil depths. The soil productivity index was calculated by summing the products of sufficiency of available water capacity, aeration, bulk density, pH, electrical conductivity, and the weighting factor for each layer. The study revealed that germination percentage and rate decreased significantly with increasing salt concentrations. The effects of the three tree species on soil properties were significantly different at 12.2 dS m(-1) salinity level compared to the control. A. tortilis was the least salt sensitive. Balancing the key requirements of adequate germination and growth and the ability to reduce the salt concentration of the soil solution, B. aegyptiaca is the species with the most potential. Therefore, the study suggests to use B. aegyptiaca as agroforestry trees in the form of parkland in arid and semi-arid areas where salinity problems are prominent.