According to a new study by researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences, the vitamin C industry may offer an unexpected resource for sustainable agriculture. They found that a byproduct of vitamin C fermentation can improve soil biological activity and crop performance. Under field conditions, it increased maize grain yield by 8.26% to 13.46%.

The findings were published in the Journal of Environmental Management.

China is the world's leading producer and supplier of vitamin C, with an annual production capacity of around 200,000 metric tons. The manufacturing process generates approximately 40,000 tons of residue after evaporation (RAE) each year. RAE is the concentrated liquid remaining after industrial fermentation and evaporation. Although RAE contains abundant organic matter and low-molecular-weight organic acids that could benefit soils, improper disposal may create environmental problems due to its high acidity and high organic load. Developing practical ways to recycle this industrial byproduct could therefore help reduce waste while supporting greener agricultural production.

In a three-year field experiment conducted in the semiarid farmlands of Fuxin, Liaoning Province, Dr. CHENG Haotian, together with Dr. SUN Hao, XU Hui and their colleagues found that applying RAE substantially improved soil nutrient availability. Levels of dissolved organic carbon, which serves as a readily available energy source for soil microorganisms, increased significantly, as did the availability of mineral nitrogen in forms that plants can readily absorb, such as ammonium and nitrate.

The researchers also found that RAE stimulated soil biological activity. Soil microbial biomass and respiration increased, and the activities of enzymes involved in carbon, nitrogen, and phosphorus cycling increased as well. Concurrently, the abundance of microbial functional genes involved in these cycles increased, suggesting that the soil microbial community could decompose organic matter more efficiently and release additional nutrients for plant growth.

These improvements in the soil environment were accompanied by measurable changes in maize physiology. Plants treated with RAE showed higher photosynthetic rates and greater chlorophyll content, allowing them to capture and convert solar energy into biomass more efficiently.

The treatment also promoted the translocation of accumulated dry matter from stems and leaves into developing kernels, improving the grain-filling process, a critical stage during which starch and other storage compounds are deposited in the grain. As a result, maize grain yields increased by 8.26% to 13.46%. Yield measurements collected from 2023 through 2025 confirmed the consistent effect across multiple growing seasons.

According to the researchers, these findings suggest a pathway through which the industrial byproduct promotes crop production. RAE enhances the supply of available soil nutrients, strengthens microbial functions involved in nutrient cycling, improves key physiological processes in maize, and ultimately supports higher grain yields.