Abstract
Intensification of rainfed agriculture in the Ethiopian highlands has resulted in soil degradation and hardpan formation, which has reduced rooting depth, decreased deep percolation, and increased direct runoff and sediment transport. The main objective of this study was to assess the potential impact of subsoiling on surface runoff, sediment loss, soil water content, infiltration rate, and maize yield. Three tillage treatments were replicated at five locations: (i) no tillage (zero tillage), (ii) conventional tillage (ox-driven Maresha plow, up to a depth of 15 cm), and (iii) manual deep ripping of the soil’s restrictive layers down to a depth of 60 cm (deep till). Results show that the posttreatment bulk density and penetration resistance of deep tillage was significantly less than in the traditional tillage and zero-tillage systems. In addition, the posttreatment infiltration rate for deep tillage was significantly greater, which resulted in significantly smaller runoff and sedimentation rates compared to conventional tillage and zero tillage. Maize yields were improved by 6% under deep tillage compared to conventional tillage and by 29% compared to no tillage. Overall, our findings show that deep tillage can be effective in overcoming some of the detrimental effects of hardpans in degraded soils.
Highlights
The Ethiopian highlands are suffering from extensive resource degradation [1,2]
The lowest bulk densities were observed in the surface 0–20 cm soil depth, while the highest were observed from 40–60 cm depth
Bulk density values for the deep tillage (DT) treatment were significantly less than those measured in the conventional till (CT) and NT treatment for the three soil depths in both years (p < 0.01)
Summary
The Ethiopian highlands are suffering from extensive resource degradation [1,2]. Hardpan formation, and declining soil quality act together to decrease agricultural productivity and economic growth in these landscapes [2,3]. (Life on Land) [4], further land degradation should be prevented. To do this information is needed on biophysical methods that will accomplish that. Land degradation and hardpan formation in the Ethiopian highlands has been related to repeated cross-plowing of steep slopes [5], compaction by heavy agricultural implements [6], and cattle grazing [7]. In a recent study [8], soil degradation was strongly related to continuous tillage after deforestation. Tillage increases the rate of mineralization and the disintegration of aggregates, which subsequently results in finer soil particles that move down the soil profile during rainfall
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