Improving Sustainable Vegetable Production with Biochar and Chitosan Xerogel Combination Under Water and Fertilizer Stress

Global warming has intensified water scarcity, while excessive fertilizer use has caused soil acidification and limited nutrient availability. This study investigated the effects of biochar and chitosan xerogel on water spinach (Ipomoea aquatica Forsk.) growth under water- and fertilizer-deficient conditions. Individually, either biochar or chitosan xerogel provided limited improvement. However, the combined application of 4% biochar and 0.8% chitosan xerogel significantly restored plant performance. Under water deficiency, fresh, stem, and leaf weights increased by 1.2-, 1.3-, and 1.7-fold, while plant height and stem diameter rose by 1.2- and 1.3-fold. Similar improvements were observed under fertilizer deficiency, with up to 1.3-fold, 2.0-fold, and 1.4-fold increases in fresh, stem and leaf weight. Chlorophyll and β-carotene contents were also enhanced under both stress conditions. Additionally, the dual amendment improved uptake of nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and manganese (Mn), achieving growth comparable to optimal irrigation and fertilization. These findings demonstrate the synergistic potential of biochar and chitosan xerogel to enhance water and nutrient efficiency, supporting sustainable agriculture under resource limitations.