Short-term effects of bench terraces on selected soil physical and chemical properties: landscape improvement for hillside farming in semi-arid areas of northern Ethiopia

Abstract

Land degradation such as declining soil fertility is the main cause for poverty in rural areas of developing countries due to reduced land productivity. To tackle the effect of soil degradation on agricultural production, soil and water conservation (SWC) measures such as bench terraces have been installed at large scale in Ethiopia highlands. However, the effects of such bench terraces on the evolution of selected soil properties are less studied. Thus, the overall objective of this study is to evaluate short-term effects of bench terraces on soil properties. Four terraced hillside farming sites and four adjacent control sites were purposely selected at Teshi, Ruba Feleg, Mechael Emba and Enda Chena of the Tigray region. For each selected site, three representative hillslope classes at foot slope, middle slope, and upslope positions were identified for soil sampling. Soil physico-chemical properties were analyzed using standard laboratory procedures at regional soil laboratory research center. The results revealed remarkable effects of bench terraces on rehabilitation of the degraded soils. However, its installation can also induce considerable negative impacts on soil fertility during the first few years due to soil translocation and exposure of subsoils. The results indicated that aggregate stability and soil pH values for most of the hillside farming sites have shown a significant difference (p ≤ 0.05) among upslope, middle and foot slopes positions and control sites which would be explained by erosion and leaching in the upslope and enrichment of base forming cations and clay at foot slope positions. High proportion of large aggregates size is observed at both Teshi and Ruba Feleg hillside farming sites compared to their corresponding control sites. The soil organic matter (SOM) content, total nitrogen (TN) and available phosphorous (Av.P) at Teshi site, TN at Ruba Feleg site, TN and Av.P at Michael Emba site and SOM and Av.P at Enda Chena hillside farming site are significantly different (p < 0.05) among the three slope classes of the sites and the corresponding control site. Moreover, mean SOM content and Av.P at Ruba Feleg site and SOM content at Michael Emba site have shown a significant difference (p < 0.05) among the three slope classes and the control sites except between upslope and middle slopes. Generally, the installation of bench terrace combined with soil fertility management practices such as application of organic manure and compost are important positive operation for changing most unproductive mountains and hillslopes into productive landscapes while contributing towards a sustainable land management in the area. This study provides important evidences on the effects of bench terraces on soil physical and chemical properties of the area to land managers and decision makers to aid sustainable land management practices in similar environments.