Biochar and compost as soil amendments: effect on sweet pepper ( Capsicum annuum L.) growth under partial root zone drying irrigation

Coarse textured soils with water scarcity significantly restrict the productivity and sustainability of agriculture, particularly in arid regions. The effects of the partial root zone drying irrigation strategy (PRD) and different organic soil amendments on sweet pepper growth, yield, and water-use efficiency (WUE) in sandy soil were surveyed. PRD consisted of two treatments: IR1 (80% ETc) and IR2 (100% ETc). Amendments consisted of biochar (BC), compost (Comp), and their mixture. The results showed that a reduction in the water supply (IR1) caused significant decreases in the morphological traits of pepper plants during flowering, fruit setting, and vigorous fruit-bearing stages. However, vegetative growth stage is not sensitive to such treatment. Plants under IR1 had higher reductions in fresh and dry weight partitioning of all plant parts (root, stem, leaf, and fruit), fruit number, and total yield compared to those under IR2. However, the WUE value was 21.6% higher than those under IR2. Integrated application of BC 2% + Comp 2% showed clear and positive effects on plant growth (plant height, stem diameter, and number of leaves), yield, and WUE, followed by Comp 4%. On the other hand, amending plants with BC 2% + Comp 2% under the full water level (IR2) generated the greatest yield improvement (70.4%). However, such treatment under IR1 gave a moderate improvement (39.9%) in yield with a higher WUE (103.8%) than the control (no organic applying under IR2). Thus, the application of BC 2% + Comp 2% with PRD (80% ETc) could be a good management strategy to enhance the productivity of sweet pepper, while saving approximately 22.0% of applied water. Information from such studies will help vegetable producers make proper decisions about increasing productivity or saving water to be allocated for greenhouse production of pepper in arid regions under water scarcity conditions.