Seven years resource-conserving agriculture effect on soil quality and crop productivity in the Ethiopian drylands

Abstract

Resource-conserving agriculture (RCA) aims at improving soil quality and crop yield whilst maintaining or improving soil health by minimizing soil disturbance, retaining crop residue, using crop rotations and adding in situ soil and water conservation tillage practices (terwah and derdero) in crop fields. In Ethiopia, intensive mining of soil resources using repeated tillage, complete crop residue removal at harvesting, overgrazing and biomass burning in croplands have aggravated soil degradation. We studied the impact of two RCA (derdero+ (DER+) and terwah+ (TER+) on long-term soil quality and crop productivity in permanently kept plots in northern Ethiopia 7 years after its inception. The two RCA practices: (i) DER+ is a bed and furrow planting system, where beds remain unploughed, furrows are tilled once at planting time and 30% of crop residue is retained. (ii) TER+ is ploughed once at planting, furrows are made at 1.5m intervals, creating fresh broad beds, and 30% crop residue is retained. These RCA practices were compared against conventional tillage (CT) characterized by a minimum of three tillage operations and complete removal of crop residues. Among the several assessed soil properties, soil organic C (SOC), total soil N, available P, soil microbial biomass C (SMBC), time of ponding, aggregate stability index (SI), consistency index (CI), cone index, air capacity and macroporosity were shown to increase significantly in soils subjected to DER+ planting system compared to CT. On average, crop yields under DER+ and TER+ increased by 30 % and 16 %, respectively, as compared to CT. Thus, from an agro-ecological point of view, adopting improved local practices such as DER+ and TER+ planting systems that employ conservation agriculture principles proved to be sustainable, resource conserving alternatives and incentives should be provided to facilitate larger adoption by farmers in Ethiopia.