Effect of homegarden and parkland agroforestry practices in Ethiopia on selected soil properties

Abstract

Ethiopian agricultural lands are fragile due to inherent unfavourable soil properties, over-exploitation, mismanagement (deforestation, over-grazing and inappropriate land use systems) and harsh weather conditions. These factors are worsened by changing climatic conditions, leading to significant problems in terms of soil erosion and loss of soil fertility. The consequences of such processes can be detected at the economic (agricultural production is currently being jeopardized) and biological (risks of biodiversity loss and habitat fragmentation) levels. However, the use of tree/shrub species in various agroforestry practices can increase soil nutrient supply through nitrogen fixation, improve soil structure, reduce soil erosion and nutrient losses. A study was carried out in the Amhara region, Ethiopia to evaluate the effect of homegarden and parkland agroforestry practices on selected soil chemical properties. Soil samples were taken from 20x20m square plots established in homegarden agroforestry and adjacent agricultural land without trees (control). In parkland agroforestry practice, two dominant tree species in each of the five villages were chosen. Soil samples were taken from the tree at the midpoint of the canopy projection, at 0-15 and 15-30 cm depths. The collected soil samples were air-dried, homogenized and passed through a 2 mm sieve for subsequent soil chemical analysis. The results indicated that all soil chemical properties except total nitrogen were significantly (P ≤ 0.05) affected by the agroforestry practices. Higher soil organic carbon, organic matter, available phosphorus, and exchangeable potassium were found in the homegarden agroforestry practice, while the lowest values were recorded in without-tree fields (control). All soil chemical properties except soil pH decreased as the soil depth increased. Higher value of organic carbon, available phosphorus, and exchangeable potassium were found in the homegarden agroforestry likely because of a higher proportion of deep-rooted tree/shrub species and species belonging to the legume functional group. Therefore, the homegarden agroforestry practice can be used as an ecologically friendly and sustainable alternative to maintaining soil fertility.