The effect of growth stimulants based on humic acids from Ukrainian lignite and biochar from agricultural residues on the growth and development of lettuce (Lactuca sativa)
¹Riga Technical University, Faculty of Natural Sciences and Technology, Institute of Biomaterials and Bioengineering, Paula Valdena Street 3, K-1, LV-1048 Riga, Latvia
²Institute of Agricultural Resources and Economics, Stende Research Centre, Dizzemes, Dizstende, Libagu parish, Talsu County, LV-3258, Latvia
³Department of Oil, Gas and Solid Fuel Processing Technology, National Technical University Kharkiv Polytechnic Institute, 2, Kyrpychova Str., UA 61002 Kharkiv, Ukraine
⁴Coal Department, State Enterprise Ukrainian State Research Institute for Carbochemistry (UKHIN), UA 61023 Kharkov, Ukraine
⁵Education-Scientific Institute of Natural and Agrarian Sciences, the Bohdan Khmelnytsky National University of Cherkasy, 81 Shevchenko Boulevard, UA 18031 Cherkasy, Ukraine
*Correspondence: maryna.zhylina@gmail.com
Abstract:
Significant amounts of plant-based waste are generated annually in the agricultural and food industries, including straw, corn residues, nutshells, and fruit pits. Disposing of this waste often relies on basic methods that avoid further processing, presenting an urgent environmental challenge. One efficient solution is converting biomass into biochar, which serves as a soil amendment. Developing cost-effective recycling methods has become critical with the increasing scarcity and rising cost of raw materials. The Dnipro Lignite Coal Basin in Ukraine offers extensive lignite reserves, enabling the production of affordable, high-quality humates for soil enhancement. In this study, wheat and barley straw were pelletized with barley bran at a 90:10 ratio. Pyrolysis was conducted at 500 °C with a heating rate of 5 °C·min⁻¹ and a one-hour holding time. The resulting biochar was added to a lettuce cultivation substrate at a 1:10 biochar-to-peat ratio. Humic substances derived from lignite were applied in 3% and 9% aqueous solutions, and environmental conditions, such as humidity and temperature, were monitored throughout the 35-day trial. Results showed that granulated biochar increased lettuce rosette diameter by 7.5% compared to perlite substrates and by 11.6% compared to peat. Additionally, 3% humate solutions enhanced rosette diameter by 11.6% and biomass weight by 25.77%. These findings confirm that biochar from agricultural residues and lignite-derived humates effectively boost lettuce yield and quality.
Key words:
agricultural residues, Agro-ecology, biochar, biomass, carbon cycle, crop, growth stimulants, Lactuca sativa, lignite-derived humates, renewable resources, soil quality