Optimizing Cropping Systems Using Biochar for Wheat Production Across Contrasting Seasons in Ethiopian Highland Agroecology

Biochar has recently emerged as a promising resource for enhancing crop productivity by improving the soil quality. However, there is limited understanding of how varying application rates of biochar combined with inorganic fertilizers impact crop productivity across diverse biophysical contexts. This study investigated the effects of different rates of water hyacinth-derived biochar and fertilizer application on wheat production during the rainy and dry seasons. Four biochar rates (0, 5, 10, and 20 t ha⁻¹), three NPS fertilizer rates (0, 100, and 200 kg ha⁻¹), and two irrigation levels (50% and 100%; for the dry season only) were evaluated for wheat yield and profitability with a randomized complete block design. Soil amendment with both biochar and fertilizer improved wheat grain yield by 6.4% in the dry season and by 173% in the rainy season. Optimal grain yields were achieved with 10 t ha⁻¹ of biochar and 200 kg ha⁻¹ of fertilizer in the rainy season, whereas in the dry season, the highest yield was observed with 20 t ha⁻¹ of biochar and 200 kg ha⁻¹ of fertilizer under the full water requirement. Specifically, for the dry season, plant height, leaf area, soil plant analysis development (SPAD) of leaf value, dry biomass, spike length, spikelet number, and grain number significantly improved due to biochar and fertilizer application. Furthermore, reducing irrigation to 50% did not significantly affect growth and yield components when the soil was amended with biochar. The highest net return (5351 and 3084 USD ha⁻¹) was achieved with 10 t ha⁻¹ of biochar and 200 kg ha⁻¹ of fertilizer during the rainy and dry seasons, respectively. This study suggests that maximum yield improvement and economic benefits can be obtained through the combination of biochar application, appropriate fertilizer rates, and water management strategies in rainfed and irrigated cropping systems.