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)

M. Zhylina¹²*, P.P. Karnozhytskyi³, D. Miroshnichenko³⁴, V. Konohrai⁵, V. Sterna² and J. Ozolins¹

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

Evaluation of different lighting sources on the growth and chemical composition of lettuce

D. Sergejeva¹, I. Alsina¹*, M. Duma², L. Dubova¹, I. Augspole², I. Erdberga¹ and K. Berzina³

¹Latvia University of Life Sciences and Technologies, Faculty of Agriculture, Institute of Plant and Soil Science, Liela street 2, LV-3001 Jelgava, Latvia
²Latvia University of Life Sciences and Technologies, Faculty of Food Technology, Department of Chemistry, Liela street 2, LV-3001 Jelgava, Latvia
³Riga Technical University, Faculty of Power and Electrical Engineering, Kalku street 1, LV-1050 Riga, Latvia
*Correspondence: ina.alsina@llu.lv

Abstract:

Experiment were carried out in Latvia University of Agriculture in plant growth room. Lettuce Lactuca sativa L. var foliosum cv. ‘Dubacek’ and L .sativa L. cv. ‘Michalina’ were grown under 4 types of lights (luminescence lamps, commercial light emitting diodes (LED) lamps (V-TAC premium series – for plant growing) and two different Lumigrow LED strips – dominant wavelength- blue or red with 14 h photoperiod and total photosynthetic active radiation (PAR) 100 μmol m^-2 s^-1 in all variants. Plant weight, length, amount of leaves were measured. Content of chlorophylls, carotenoids, phenols, flavonoids in lettuce was determined three times per vegetation period. In experiments were found that higher lettuce yield was under commercial LED (V-TAC premium series), but these plants contain less soluble sugars, pigments and phenols. Better plant quality was obtained with luminescence lamps. These lettuces have higher sugar, phenols and flavonoids content. Lettuce growth under blue dominate LED (LEDb) was delayed, but these plants contain higher chlorophylls content. The differences in plant growth, response to light and biochemical content between cultivars were detected.

Key words: