Influence of indigenous parkland agroforestry trees on soil physicochemical properties in the Baskura Watershed, Northwest Ethiopia

Abstract

Abstract Soil fertility degradation has become a major challenge resulting in low crop productivity and food insecurity in sub-Saharan Africa. Indigenous scattered trees such as Acacia abyssinica, Albizia schimperiana, Croton macrostachyus and Olea africana are purposively maintained on farmlands to improve soil fertility and crop productivity. However, there has been limited evidence on the effects of those trees on soil properties. Hence, the study aimed to examine effects of A. abyssinica, A. schimperiana, C. macrostachyus and O. africana trees and radial distances on soil physicochemical properties in Baskura Watershed, Northwest Ethiopia. Soil samples were collected from 0–20 cm depth at three radial distances (under canopy, canopy edge and outside the canopy) of each tree trunk. The collected data was analyzed using analysis of variance. Results revealed significant ( p < 0.05) differences in soil pH, soil organic carbon (SOC), total nitrogen (TN), available phosphorus (Av P), cation exchange capacity (CEC) and exchangeable potassium (Ex K) among tree species and radial distances. The average values of soil pH (6.36 and 6.25), SOC (3.46 and 2.93%), Av P (10.42 and 8.66 mg kg −1 ), CEC (38 and 36.66 cmol kg −1 ) and Ex K (2.34 and 2.31 cmol kg −1 ) were higher under the canopies of C. macrostachyus and A. abyssinica , respectively. However, the highest TN (0.46%) was recorded under the canopy of A. abyssinica . Moreover, soil nutrients decreased with increasing distance from the tree trunks. The contribution of tree species to soil properties improvement follows the order C. macrostachyus > A. abyssinica > A. schimperiana > O. africana . Hence, integrating indigenous trees such as C. macrostachyusand and A. abyssinica on croplands can improve soil properties and nutrient availability. However, further study need to be conducted to examine effects of tree species on soil properties, litter quality and decomposition dynamics under different agroecological conditions.