Interrelationships between terrace development, topography, soil erosion, and soil dislocation by tillage in Minchet Catchment, Ethiopian Highlands

Abstract

This study assesses the interrelationships between terrace development and topographic factors, soil erosion, and soil dislocation by tillage in Minchet Catchment in the Ethiopian Highlands. Data were collected through a mix of modelling soil erosion using the Universal Soil Loss Equation adapted to Ethiopia, and measuring slope and soil deposition above the terraces. The terraces, which developed over 29 years following construction of fanya juu bunds on cropland, reduced the cropland's current slope gradient to half of its original slope, leading to about 39% less soil erosion. Currently, of the total 50 t · ha−1 · yr−1 soil deposition measured above the terraces, about 22 t · ha−1 · yr−1 was soil eroded by water, and the other 28 t · ha−1 · yr−1 was soil that had been dislocated by tillage. This shows that Soil and Water Conservation technologies in the study area are effective in reducing slope gradient and slope length, and thus also in trapping eroded soil, slowing soil movement by tillage, and ultimately, in reducing soil erosion. However, current soil loss from the fields still exceeds the soil formation rate of the study area. We thus highlight possible options to further reduce soil erosion in the crop fields, such as increasing the number of terraces in areas with wider spacing and growing multipurpose and productive grasses and trees on terraces.

GUEST EDITORIAL—SPECIAL ISSUE: Mapping and modelling soil erosion to address societal challenges in a changing world

“…Yang and Lu (2018) applied a water erosion model to assess the efficiency of soil water conservation measures within the Green‐for‐Grain Program on the Chinese Loess Plateau. Subhatu et al (2018) used a similar approach for evaluating the efficiency of fanya juu bunds on water and tillage erosion in Ethiopia. Taye et al (2018) also focused on Ethiopia, assessing the effectiveness of soil water conservation measures by plot monitoring in semi‐arid range lands and croplands.…”

Multicriteria evaluation to identify potential areas for level Fanya juu terrace in Central Ethiopia

“…Therefore, the study area has min-max ranges of elevation (1893-2513 m.a.s.l.) and rainfall (900-1400 mm) were considered and the mean percentage of soil loss reduced (77%) of Minchet catchment (Subhatu et al 2018) and Maybar and Hunde Lafto (Herweg and Ludi 1999) were taken to estimate a potential reduction of soil loss using level Fanya juu terrace (Table 4). 1; Used to estimate an expected percentage of soil loss would be reduced from level Fanya juu.…”

“…According to reference proportion (Herweg and Ludi 1999;Subhatu et al 2018), 77% of soil loss will be presumed to be reduced after implementation of level Fanya juu terrace (Table 7). Accordingly, in areas prominently in need of level Fanya juu terrace, the soil loss will be expected to reduce from 105,990 tons/ha/year to 4,378 tons/ha/year (Table 7).…”

“…However, the ex-ante reduction on soil loss needs considerable attention in terms of technical and socioeconomic collaboration. As a result, the gradual enrichment of the level Fanya juu terrace would have a signi cant contribution to improving crop/biomass yield and reducing soil loss below the tolerable limit(Subhatu et al 2018;Wolka et al 2018; Alemu and Melesse 2020; Mekonnen 2021). In the end, level Fanya juu terrace is expected to reduce soil/sediment loss(Subhatu et al 2017(Subhatu et al , 2018 and costs of land degradation due to soil erosion by water(Gebreselassie et al 2016).…”

Conversion of Slope Cropland to Terrace Influences Soil Organic Carbon and Nitrogen Stocks on the Chinese Loess Plateau

“…The Loess Plateau has received widespread attention because of its thick loess and extreme soil and water losses [9,10]. Terrace construction, an agriculture method used to conserve soil and water, can efficiently reduce soil and water loss from sloping farmlands and can increase yields in arid regions [11,12]. Terrace is important with respect to maintaining food security and ecological security in ecologically fragile areas [13,14].…”