EFFECTS OF Eucalyptus camaldulensis Dehnh AND Croton macrostachyus Del ON SELECTED SOIL CHEMICAL AND PHYSICAL PROPERTIES IN NITSOILS IN BISHO WATERSHED, SOUTHERN ETHIOPIA

In the past, Ethiopia was rich in natural resources. As population pressure increased, resources have been exploited greatly. In the study area the need to expand cultivated has led to the removal of well-adapted, nutrient additive indigenous trees. The study was conducted in Bisho watershed, Southern Ethiopia, to evaluate the Effect of Eucalyptus camaldunesis Dehnh. and Croton macrostachyus Del. and distance away from tree trunk on selected soil chemical and physical properties in Nitisols. Soil samples were collected from four different distances (1, 3, 6, and 10 meters) away from tree trunk. A total of 8 composite soil samples were collected from both Eucalyptus camaldunesis and Croton macrostachyus stands from the surface (0-20 cm) soil depth and replicated three times. Except particle size distribution, bulk density, available phosphorus and exchangeable sodium, all the other soil properties were significantly (P < 0.05) affected by tree species. All the other soil properties, except particle size distribution, bulk density, available phosphorus, exchangeable potassium and sodium, all the other soil properties studied showed significant (P < 0.05) differences due to variations in horizontal distance from tree trunk of both species. Among soil parameters that were significantly different, except exchangeable acidity, the mean values of all the other properties were higher in soil under Croton macrostachyus than Eucalyptus camaldunesis and near the tree trunk than away from the tree trunk of both trees. The results showed that the quality of the soil under the indigenous Croton macrostachyus was much better than that under the exotic Eucalyptus camaldunesis tree. Regardless of the positive influence of the indigenous tree on most soil properties, the soils are strongly to moderately acidic, low in organic matter and total nitrogen content, available P, Ca, Mg, Fe and Cu and therefore require integrated soil fertility management in order to improve crop productivity. The finding of this study implied that croton macrostachyus significantly improve soil chemical properties as compared to Eucalyptus camaldunesis.