Declining soil fertility and rising mineral fertilizer costs severely constrain wheat production in Ethiopia, threatening food security. Bio-slurry from biogas digesters offers a potential low-cost organic amendment, but limited field evidence exists on its integrated use with chemical fertilizers. A two-year field experiment (2023/2024–2024/2025) was conducted at the University of Gondar Shinta Research Farm, northwestern Ethiopia. Six treatments: control (no amendment), 100% chemical fertilizer (CF: 100 kg N ha⁻¹ as urea + 100 kg NPS ha⁻¹), 75% CF + 25% bio-slurry (BS), 50% CF + 50% BS, 25% CF + 75% BS, and 100% BS (10 t ha⁻¹ dry weight) were arranged in a randomized complete block design with three replications. Wheat agronomic parameters, grain yield, soil physicochemical properties, and heavy metal concentrations (Pb, Cd, Cr) were analyzed using standard methods. Integrated BS and CF applications significantly improved all agronomic parameters compared to sole CF or control (p < 0.05). The 25% CF + 75% BS treatment produced the highest aboveground dry biomass (9.5–11.1 t ha⁻¹) and grain yield (2.8–4.4 t ha⁻¹), representing 40–60% increases over sole CF. Post-harvest soil analysis revealed significant increases (p < 0.05) in pH (from 5.6 to 8.0), organic carbon (from 1.8% to 15.8%), organic matter (from 3.2% to 27.5%), total nitrogen (from 1.0% to 2.2%), and available phosphorus (from 1.4% to 1.9%) under BS-amended treatments. Heavy metals (Pb, Cd, Cr) in both soil and wheat grain remained below detection limits, confirming food safety. Partial substitution of chemical fertilizer with bio-slurry at 25% CF + 75% BS enhances wheat productivity and soil fertility while reducing mineral fertilizer dependence by 75%. This integrated nutrient management strategy offers a sustainable, economically viable approach for smallholder farmers in Ethiopian highlands, supporting circular economy principles through organic waste recycling.
Amare et al. (Wed,) studied this question.