Effects of plant-waste–derived biochars on soil properties, biochemical composition, and sensory quality of water spinach (Ipomoea aquatica Forsk.)

Biochar derived from agricultural and food wastes offers a sustainable means of enhancing soil fertility and crop quality. However, most studies have focused solely on soil and yield responses, overlooking its potential effects on the nutritional and sensory quality of edible crops. This study therefore evaluated the effects of feedstock-specific, waste-derived biochars on soil properties, agronomic performance, biochemical composition, and sensory quality of Ipomoea aquatica . Biochars produced from coffee grounds, cocoa shells, corn cobs, and longan wood were evaluated against a control (no biochar) in a 30-day cultivation system. Biochar amendments differentially influenced soil chemistry: cocoa shell and coffee ground biochars exhibited the strongest liming effects, while corn cob and cocoa shell biochars most effectively enhanced soil organic matter (OM), with increases of 72% and 73%, respectively. Agronomic performance improved across all biochar treatments, with corn cob biochar achieving the highest yield (+67%) and root biomass (+21%), whereas coffee ground biochar showed the lowest improvements (+20% and +13%, respectively). In terms of plant height, coffee ground, longan wood, and cocoa shell biochars produced 24%, 23%, and 20% taller plants, respectively. Nutritional analysis revealed that corn cob biochar produced the highest levels of umami amino acids and sweetness-associated alanine; marked increases in soluble sugars (glucose +215%, sucrose +103%); correspondingly higher equivalent umami concentration (EUC amino ), taste activity value (TAV)-Umami, and TAV-Sweet indices; and elevated pigment contents (chlorophyll +209%, anthocyanins +83%). Chef panels favored crops grown with corn cob biochar and rated those from coffee ground biochar lowest. Overall, the feedstock type of biochar influenced not only soil and plant growth but also the nutritional and sensory quality of the produce. Among the tested biochars, corn cob biochar demonstrated the best overall performance, underscoring the promise of waste valorization for producing sustainable and consumer-preferred crops. • Feedstock-derived biochars enhanced soil, yield, and crop quality. • Corn cob biochar increased yield, sugars, and umami taste quality. • Cocoa shell biochar improved soil organic matter and plant biomass. • Longan wood biochar increased sucrose and total carbohydrate content. • Coffee ground biochar produced taller plants but increased soil EC.