Can degraded soils be improved by ripping through the hardpan and liming? A field experiment in the humid Ethiopian Highlands

Abstract

Land degradation in developing countries is exacerbating hardpan development that causes the formation of perched watertable, which in turn results in increased runoff and erosion. To reduce overland flow and erosion, percolation through the hardpan needs to be improved. One successful way to achieve this is ripping off the hardpan and plausibly liming. However, in the highlands of Ethiopia, there is little information available on these two techniques. The objectives of this study were, therefore, to determine the effects of ripping off degraded soils on runoff and erosion rates and whether liming would improve the effectiveness of ripping. A field study was conducted in the Anjeni watershed. Thirty‐two experimental runoff plots were installed across the watershed. Conventional tillage at 15 cm depth and ripping to 30, 45, and 60 cm depths were applied with and without lime amendments. Results showed that ripping to 60 cm depth resulted in a significant reduction of runoff. However, liming increased runoff response, on average by 10%. In contrast to the reduction in runoff amounts, an increase in ripping depth increased the amount of soil loss especially during the first storms at the beginning of the monsoon rainy season. Liming significantly decreased soil loss by up to 35%. Although plots with deep ripping plus liming had greater runoff production than other plots, soil loss was less. Overall, the findings suggest that deep ripping has promise but more research is needed before widely implemented.

Hydrogeology of Volcanic Highlands Affects Prioritization of Land Management Practices

“…The current study was carried out in the Ethiopian Highlands, which are similar to volcanic highlands elsewhere with highly conductive topsoil, subsurface interbasin transfers of water, and a large population that depends on the natural resource base for ecological services, both in the highlands and downstream. The land in the highlands is becoming increasingly degraded with the shift to continuous cultivation of crops to feed the rapidly increasing population, resulting in a loss of organic matter and subsequent hardpan formation affecting the recharge and surface runoff processes [26][27][28]. This, in turn, is threatening the natural resources base and the associated ecological services [29][30][31][32][33].…”

Improving Hydrologic Simulations of a Small Watershed through Soil Data Integration

“…Land and water management is at a critical junction in the Ethiopian highlands. Traditional land management practices (e.g., fallowing, shifting cultivation) are becoming less common due to shortage of arable land [1][2][3][4][5]. This is primarily due to the increased population and the need for more farmlands and/or animal grazing [6].…”