Exogenous application of wood vinegar improves rice yield and quality by elevating photosynthetic efficiency and enhancing the accumulation of total soluble sugars

Rice is an important cereal crop for over half of the world population and essential for food security, especially in developing countries where it constitutes a substantial part of daily caloric intake. Wood vinegar, obtained from biomass pyrolysis and rich in organic acids, phenols, esters, sugars, and alcohols, promotes crop growth and productivity. Its diverse composition offers an eco-friendly and cost-effective growth promoter and improves stress tolerance in different crops; however, its optimal application timings in rice cultivation remain underexplored. Our study investigated the effects of wood vinegar on rice growth, photosynthetic efficiency, chlorophyll contents, soluble sugars, phenolics, grain chalkiness, and yield at different stages and combinations such as tillering (T), jointing (J), flowering (F), grain filling (G), T + J, T + F, T + G, J + F, J + G, F + G, T + J + F, T + J + G, T + F + G, and J + F + G. Our results indicate that wood vinegar application at T + J + F stages significantly enhanced the photosynthetic rate by promoting gaseous exchange, chlorophyll contents, and SPAD index when compared with control. Additionally, total soluble sugars (9.71 mg g⁻¹) and phenolics (2.4 mg g⁻¹) levels were noticeably induced during wood vinegar application as compared with corresponding control. Besides, this treatment also elevated the yield by up to 32.4%, reduced grain chalkiness, and enhanced head rice percentage. Taken together, these findings suggest that wood vinegar supports sustainable agriculture by improving crop yield and quality, offering considerable benefits to farmers.