Abstract
Abstract. Adoption of soil conservation structures (SCS) has been low in high rainfall areas of Ethiopia mainly due to crop yield reduction, increased soil erosion following breaching of SCS, incompatibility with the tradition of cross plowing and water-logging behind SCS. A new type of conservation tillage (CT) involving contour plowing and the construction of invisible subsoil barriers using a modified Maresha winged "subsoiler" is suggested as a means to tackle these problems as an integral part of the SCS. We investigated the effect of integrating the CT with SCS on the surface runoff, water-logging, soil loss, crop yield and plowing convenience. The new approach of conservation tillage has been compared with traditional tillage (TT) on 5 farmers' fields in a high rainfall area in the upper Blue Nile (Abbay) river basin. Test crops were wheat [triticum vulgare] and tef [eragrostis tef]. Farmers found CT convenient to apply between SCS. Surface runoff appeared to be reduced under CT by 48 and 15%, for wheat and tef, respectively. As a result, CT reduced sediment yield by 51 and 9.5%, for wheat and tef, respectively. Significantly reduced water-logging was observed behind SCS in CT compared to TT. Grain yields of wheat and tef increased by 35 and 10%, respectively, although the differences were not statistically significant apparently due to high fertility variations among fields of participating farmers. Farmers who tested CT indicated that they will continue this practice in the future.
Highlights
In Ethiopia, land degradation has become one of the most important environmental problems, mainly due to soil erosion and nutrient depletion
It is estimated that the transboundary rivers that originate from Ethiopian highlands carry about 1.3 billion t yr−1 of sediment to neighboring countries (MoWR, 1993), whereas the Blue Nile alone carries 131 million t yr−1 (Betrie et al, 2011) and 61 million t yr−1
Adoption of SCS in high rainfall areas in the upper Blue Nile (Abbay) river basin, in Ethiopia is constrained by reduced crop yield, accelerated soil erosion due to frequent breaching of SCS, which in turn is caused by higher surface runoff from plowing up and down the slope
Summary
In Ethiopia, land degradation has become one of the most important environmental problems, mainly due to soil erosion and nutrient depletion. Different literatures show an escalating threat of land degradation in the highlands (Hurni, 1993). Average soil loss rates on croplands have been estimated at 42 t ha−1 yr−1 but may reach 300 t ha−1 yr−1 in individual fields (Hurni, 1993). Taddesse (2001) estimated annual topsoil loss due to soil erosion in the highlands of Ethiopia, which accounts for 44 % of the total area, to be 1.5 billion t yr−1. The 2008 report of FAO indicated that during the period 1981–2003, the total land degraded in Ethiopia is estimated to be 297 000 km (Bai et al, 2008). Poor watershed management and inappropriate farming practices have contributed to these escalating rates
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