Conservation agriculture-based resource saving technology for land resilience in northern Ethiopia

Conventional soil cultivation practices have resulted globally in land degradation. The main causes of cropland degradation in northern Ethiopia are repeated plowing, complete removal of crop residue at harvest leaving no soil cover and aftermath overgrazing of the crop field. Conservation Agriculture (CA) system was combined with in-situ soil and water conservation practices, can lead to reduced runoff, soil and nutrient loss, and to increased amount of green water, crop yield, profitability and thereby, sustainability. Two medium-term tillage experiments were carried out (2005 to 2011) on a Vertisol to quantify changes in runoff, soil loss, soil fertility, soil moisture, soil quality, crop and economic productivity of two local conservation tillage practices modified to comply with CA principles, namely, derdero and terwah, in two contrasting agro-ecological zones in northern Ethiopia. The experimental layout was implemented in a randomized complete block design with three replications on permanent plots. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, 30% standing crop residue retention and no-tillage on top of the bed, (ii) terwah+ (TER+) with plowing once at planting, 30% standing crop residue retention and fresh broad beds, and (iii) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues. Wheat, hanfets (mixture of barley and wheat) and grass pea (Lathyrus sativus) crops were grown in rotation at the May Zegzeg catchment, while wheat, teff, barley (Hordeum vulgare) and grass pea crops were grown in rotation at the Gum Selasa experimental site. Glyphosate was sprayed starting from the third year (2007) at 2 l ha-1 before planting to control pre-emergent weed in DER+ and TER+. Our study demonstrated that the introduction of the CA based conservation practices had a positive effect on runoff, soil and nutrient loss, soil quality, green water, crop yield and economic performance, we argue that the avoidance of repeated tillage, requiring 10 to 16 oxen-span days per ha, depending on crop type and year, and the faster plowing pace at planting in DER+, will enable a reduction in oxen density with further natural resource benefits