The Journal of Agriculture and Food Research recently highlighted the work of researchers Ruogu Tang and Juzhong Tan, who have developed a innovative substrate for growing lettuce microgreens. Their study addresses a common problem in soil-free farming: the lack of inherent nutrients and water stability in standard hydrogels. By integrating biochar, a charcoal-like substance made from organic waste, into a clear plant gel called phytagel, they created a material that provides both structural support and life-sustaining resources. This combination proved remarkably effective, turning a simple mechanical support into an active participant in the plant’s health and development.

The physical changes brought about by the biochar were immediate and measurable. While standard gels have a smooth and simple internal structure, the addition of biochar creates a more porous and heterogeneous landscape. This increased surface area allows the substrate to hold onto more water and release it slowly as the plant needs it. Quantitatively, the water-holding capacity of the gels improved by approximately nine percent when the highest levels of biochar were used. This structural modification essentially creates a buffered root-zone environment that protects young seedlings from fluctuating environmental conditions.

When researchers tested these new gels with lettuce microgreens, the growth results were impressive. Although the biochar caused a slight delay in the very first stages of emergence, the plants quickly caught up and surpassed those grown in standard gels. By the end of a two-week growing period, the microgreens in the biochar-enriched substrates showed a forty to fifty percent increase in root length. Fresh yields were also significantly higher, with the biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More increasing steadily as more biochar was added to the mix. These findings suggest that biochar acts as a powerful growth promoter even under optimal conditions, not just when the plant is under stress.

The true value of this new substrate became clear when the researchers simulated drought conditions by lowering the humidity. In standard gels, the microgreens quickly began to wilt and lose their green color as they dehydrated. However, those grown with biochar remained turgid and vibrant. Under the most severe stress testing, the biochar-treated plants maintained over ninety percent moisture content, while the standard group fell to nearly eighty-seven percent. This resilience is linked to the biochar’s ability to act as a mineral-rich reservoir, supplying the plant with the tools it needs to regulate its internal water pressure and protect its photosynthetic machinery.

Nutritional quality also saw a major boost with this method. The microgreens absorbed higher concentrations of essential macronutrients like phosphorus and potassium, which are vital for energy transfer and overall plant vigor. Even more notable were the gains in micronutrientsThese are essential nutrients that plants need in small amounts, kind of like vitamins for humans. They include things like iron, zinc, and copper. Biochar can help hold onto these micronutrients in the soil, making them more available to plants.   More; levels of iron and zinc reached significantly higher peaks compared to the control group. These minerals are not just important for the plant’s defense systems; they also make the final crop more nutritious for human consumption. The researchers found that they could even fine-tune these nutritional profiles by choosing biochar made from different sources, such as poultry litter for more nitrogen or nutshells for better structural support.

Ultimately, this study establishes a strong proof-of-concept for using biochar-hydrogel composites in sustainable agriculture. By converting agricultural residues like corn stalks or bamboo into high-value cultivation materials, this system aligns with the goals of a circular bioeconomy. It offers a way to produce high-quality, resilient food in urban areas or other regions where good soil is scarce. While further work is needed to scale this technology for large-scale commercial use, the current findings demonstrate that we can significantly improve crop reliability and nutritional value through the strategic design of growing substrates.

Source: Tang, R., & Tan, J. (2025). Biochar-Phytagel Hydrogel Enhances Growth, Nutrient Uptake, and Drought Resilience of Lettuce Microgreens. Journal of Agriculture and Food Research.