Effect of Acacia nilotica on selected soil properties, sorghum and teff yield in parkland agroforestry, Kewot district, Amhara, Ethiopia

Abstract

The effects of Acacia nilotica on Sorghum bicolor and Eragrostis tef yield as well as selected soil properties were evaluated under traditional parkland agroforestry system in the lowlands of Kewot district, North Shewa Zone in order to contribute to understanding of this tree effects on selected soil properties, sorghum and teff yield. A total of ten Acacia nilotica trees were purposively selected based on similar canopy width, height and diameter at breast height. Treatments were laid down on sorghum and teff fields and replicated five times under Randomized Complete Block Design. Soil samples were collected at distances of 2.5m, 5m and 12m from the tree trunk with a depth of 0-10 cm, 10-20 cm and 20-30 cm for soil chemical and physical properties analysis. Soil texture and bulk density were not affected significantly (p>0.05) with distance from the tree trunk while bulk density significantly varied with soil depth (p<0.05). Soil organic carbon, total nitrogen, organic matter and phosphorus concentration increased significantly with decreasing distance from the tree base (p<0.05) and significantly declined with increasing soil depth (p<0.05). The highest soil organic carbon, soil organic matter, total nitrogen and Available Phosphorus concentrations were found under the tree canopy and in surface soil. Soil pH and C/N ratio were least affected by the presence of Acacia nilotica and not significantly varied (P>0.05) with soil depth and distance. Sorghum grain yield reduction (61%) and (32%) was found in the mid canopy and canopy edge respectively. Similarly, Teff grain yield reduction (55.72%) and (33.76%) was found at mid canopy and edge of the tree canopy, respectively. This study revealed that Acacia nilotica negatively affected the grain yield and biomass production of sorghum and teff however, improves soil organic carbon, total nitrogen, organic matter and phosphorus concentration of the soil under its canopy.