This study presents a novel biochar-fortified hydrogel cultivation system designed to enhance lettuce microgreen growth under moisture-limited conditions—an escalating challenge in controlled-environment agriculture and urban food production. Biochars derived from various biomass sources were incorporated at different concentrations (1-10% w/w) into a phytagel-based hydrogel matrix to tailor the physicochemical properties of the growing substrate for optimal plant performance.

Lettuce microgreens were cultivated under progressively reduced relative humidity (from 70% to 30%) to simulate drought stress. Experimental results demonstrated that both biochar type and dosage significantly influenced the water retention, aeration, and nutrient availability of the hydrogel substrate. These improvements translated into higher biomass yield, enhanced shoot and root elongation, and elevated chlorophyll content compared to untreated controls. Substrate characterization confirmed that biochar amendments substantially increased surface area and porosity, resulting in superior moisture-buffering and sorptive functions critical for sustaining plant growth under limited water conditions.

This work advances food technology and engineering by offering a scalable, cost-effective strategy for functional substrate engineering in soilless cultivation systems. The integration of diverse biochar types into hydrogel media represents a sustainable and circular innovation that supports water-efficient, high-density crop production—particularly relevant for vertical farming, urban agriculture, and precision farming technologies. By addressing critical resource constraints, this engineered platform has significant potential to drive resilient and sustainable food production technologies in the face of climate variability and global food security challenges.