Hardpan is a major cause of land degradation that affects agricultural productivity in developing countries. However, relatively, little is known about the interaction of land degradation and hardpans. The objective of this study was, therefore, to investigate soil degradation and the formation of hardpans in crop/livestock‐mixed rainfed agriculture systems and to assess how changes in soil properties are related to the conversion of land from forest to agriculture. Two watersheds (Anjeni and Debre Mewi) were selected in the humid Ethiopian highlands. For both watersheds, 0–45 cm soil penetration resistance (SPR, n = 180) and soil physical properties (particle size, soil organic matter, pH, base ions, cation exchange capacity, silica content, bulk density and moisture content) were determined at 15 cm depth increments for three land uses: cultivated, pasture and forest. SPR of agricultural fields was significantly greater than that of forest lands. Dense layers with a critical SPR threshold of ≥2000 kPa were observed in the cultivated and pasture lands starting at a depth of 15–30 cm but did not occur in the undisturbed forest land. Compared with the original forest soils, agricultural fields were lower in organic matter, cation exchange capacity, and exchangeable base cations; more acidic; had a higher bulk density and more fine particles (clay and silt); and contained less soluble silica. Overall, our findings suggest that soil physical and chemical properties in agricultural lands are deteriorated, causing disintegration of soil aggregates, resulting in greater sediment concentration in infiltration water that clogged up macro‐pores, thereby disconnecting deep flow paths found in original forest soils. Copyright © 2016 John Wiley & Sons, Ltd.

Gully erosion reduces agricultural productivity by destroying valuable land resources, increases sediment concentrations, reduces water quality, and fills up reservoirs. Gully rehabilitation has proven to be challenging especially in the high-rainfall areas of the Ethiopian Highlands and has therefore had limited success. This paper describes a successful low-cost gully rehabilitation effort with community participation in the Birr watershed in the Blue Nile basin that begun in early 2013. Initially, farmers were reluctant to participate for religious reasons, but with the aid of local priests and respected elders, community discussions, and a visit to a rehabilitated gully, a consensus was reached to rehabilitate a 0·71-ha upland gully. The rehabilitation measures consisted of regrading the gully head at a 45°slope, constructing low-cost check dams from locally available materials, and planting Pennisetum purpureum grass and Sesbania sesban. At the end of the first postimplementation rainy season, 2,200 tons of soil was conserved by the constructed check dams and newly planted vegetation, compared with soil losses of 680 and 560 tons in two untreated, nearby gullies. In 2014, an additional 3,100 tons of soil was conserved. In 2013, the marginal rate of return (MRR) on the gully rehabilitation investment was 2·6 based on the value of increased forage production alone. When we include trapped soil nutrient values, the rehabilitation MRR was increased to 10. Although these numbers are impressive, the best proof of the success was that farmers on their own initiative rehabilitated an additional five gullies in 2014.

In the northern highlands of Ethiopia, gully erosion is severe. Despite many efforts to implement gully prevention measures, controlling gully erosion remains a challenge. The objective is to better understand the regional gully erosion processes and to prevent gully head retreat. The study was conducted in the Ene‐Chilala catchment in the sub‐humid headwaters of the Birr River located southwest of Bahir Dar, Ethiopia. Twelve gully heads were monitored during the 2014 and 2015 rainy monsoon phase. We measured gully head morphology and retreat length, soil shear strength, ground water table levels, and catchment physical characteristics. Two active gully head cuts were treated in 2014 and an additional three head cuts in 2015 by regrading their slope to 45° and covering them with stone riprap. These treatments halted the gully head advance. The untreated gullies were actively eroding due to groundwater at shallow depths. The largest head retreat was 22.5 m, of which about half occurred in August of the first year when the surrounding soil was fully saturated. Lowering both the water table and protecting the gully heads can play a key role in reducing gully expansion and soil loss due to gully erosion in the Ethiopian highlands. Copyright © 2016 John Wiley & Sons, Ltd.

<p>General knowledge based on the good agricultural soils in temperate climates is that no-till and conservation-till practices increase infiltration of the rainwater and decrease runoff and erosion.  Experiments in the semi-humid Ethiopian highlands do not often show the same benefits and in many cases no-till actually increases runoff above conventional and deep tillage. In contrast, for conservation-tillage with mulch at the surface, more of the water infiltrates and enhances plant growth</p><p>Reduced tillage systems increase infiltration through soil fauna that form soil macropores through which rainwater flows to the subsoil bypassing the soil matrix with limited conductivity. Most degraded soils (at least in the Ethiopian highlands) have a hardpan at shallow depths restricting downward movement of water. Runoff on conventionally tilled soils is caused by saturation excess when the perched water table in the plowed soil layer reaches the surface.  Thus, the amount of runoff is determined by the water free pore space in the surface layer.  Since this pore space is less under no-till, no-till has greater amounts of runoff than conventional till. </p><p>Under mulch tillage, organic matter is introduced at the surface and soil fauna becomes well-developed which will improve the soil structure and porosity of the soil.  This structure will be maintained because the mulch decreases the sediment concentration in the water and the pores will remain open. Under conventional tillage sediment concentrations are high and any pores formed will be filled up with sediment. Our expectation is that since organic matter under mixed farming is used to feed the cattle, widespread implementation of no-till and conservation tillage will be limited to areas with high value crops in which farmers can afford using organic matter as a mulch.</p>

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