Maintaining Acacia polyacantha trees in farmlands enhances soil fertility and income of farmers in North Western Tigray, Northern Ethiopia

摘要

Acacia polyacantha is a fast growing indigenous tree legume that can be integrated with crops as parkland agroforestry system. Farmers keep Acacia polyacantha on their farmlands mainly for fuel wood, animal fodder, farm tools and construction. However, quantitative information on the effect of Acacia polyacantha on soil fertility improvement and socioeconomic benefits is lacking. The effect of Acacia polyacantha on soil fertility and its contribution to household income was evaluated in La'ilay Adiyabo district, northern Ethiopia. At three radii distances, 36 soil samples were collected from two soil depths from 24 trees in cultivated and uncultivated land using a 3 x 2 x 2 x 3 factorial arrangement in randomized complete block design (RCBD) replicated three times. The effect of planting Acacia polyacantha trees on household income was estimated using Ordinary Least Squares based on data collected from a sample of 120 randomly selected farm households. Total N, OC, OM, CEC and exchangeable K levels were significantly higher under the canopies of Acacia polyacantha than outside (p < 0.05). The nutrient levels decreased significantly with increasing soil depth. Planting Acacia polyacantha trees was found to positively and significantly influence household income, in which case the aggregated monetary value of the different products from Acacia polyacantha contributed 13.7% to total household income, which is significant. However, land size was also found to be crucial; and the role that Acacia polyacantha trees play can be further increased through efficient use and management of agroforestry land.