Enhancing camelina Camelina sativa (L.) Crantz productivity in acidic Ethiopian soils: Synergistic effects of coffee husk biochar and phosphorus

Abstract Acidic soils in Ethiopia's Hadiya Zone limit crop production through aluminum toxicity and phosphorus (P) fixation, which constrain camelina potential. Though drought tolerant, camelina needs sufficient P. Triple superphosphate (TSP) often becomes ineffective because P is rapidly fixed; coffee husk biochar may reduce fixation and improve P availability. Field experiments examined combinations of amendments to test practical options for smallholder farmers in Hadiya, Ethiopia. This study evaluated camelina growth, yield, and P use efficiency under coffee husk biochar and TSP in Hadiya. A split‐split‐plot design with three replications tested two cultivars (Zeytee‐1 and Syria), four TSP rates (0, 23, 46, and 69 kg ha − 1 ), and four biochar rates (0, 10, 12, and 14 t ha − 1 ). Biochar significantly enhanced growth: 14 t ha − 1 increased leaf area by 48% and plant height by 39%, improving vigor. Combined biochar and TSP maximized yield components; Syria doubled siliques per plant with 69 kg ha − 1 TSP plus biochar. Peak grain yields reached 2.64 t ha − 1 for Syria (46 kg ha − 1 TSP + 12 t ha − 1 biochar) and 2.60 t ha − 1 for Zeytee‐1 (69 kg ha − 1 TSP + 14 t ha − 1 biochar). Biochar raised phosphorus recovery efficiency to 10.8% when combined with 23 kg ha − 1 TSP. Cultivar responses differed: Zeytee‐1 favored higher inputs; Syria performed best with balanced fertilization. Applying 12–14 t ha − 1 coffee husk biochar with TSP (Zeytee‐1: 46–69; Syria: 23–46 kg ha − 1 ) enhances phosphorus efficiency. This practice improves marginal soil productivity and supports camelina as a viable oilseed for acidic soils.