Optimizing Yield and Water Use Efficiency of Pepper Under Deficit Irrigation Using Biochar

Present research was conducted to investigate the interactions between deficit irrigation and biochar application in pepper (Capsicum annuum L. cv. Demre Sivrisi) grown under greenhouse conditions in a sandy-loam soil with low water-holding capacity. The experiment was arranged in a 4×4 factorial design with three replications, comprising all combinations of four irrigation levels (100%, 75%, 50% and 25% of field capacity) and four biochar doses (0, 50, 150 and 250 g/5 kg). The amount of irrigation water was determined using a gravimetric method. Plant height, fresh biomass, yield and crop water consumption (ET) were measured, and water use efficiency (WUE), biomass water use efficiency (BWUE), harvest index (HI) and yield response factor (Ky) were calculated. Water deficit markedly reduced all growth and yield parameters; mean yield decreased from 1058 g per pot under full irrigation to 108 g per pot under the most severe deficit. Biochar application increased growth and yield at all irrigation levels, providing about a 35% yield increase at the highest dose relative to the control. Biochar raised the field capacity of the sandy-loam soil by 30% at the highest dose. WUE reached its maximum not under full irrigation but at the 75% irrigation level (15.9 g/L), with the highest WUE (17.0 g/L) obtained at the 75% irrigation–250 g biochar combination. Increasing biochar dose lowered the yield response factor (Ky), reducing the crop's sensitivity to water deficit. Present findings indicated that, in water-scarce regions, combining 75% irrigation with a high biochar dose was an effective strategy to maximize yield per unit water.