Effect of humic acid on the growth of seedling tomato (Solanum lycopersicum) and melon Cucumis melo)

This study evaluated the effect of HS extracted from mineral coal on the growth of tomato (Solanum lycopersicum) and melon (Cucumis melo) plants to determine the role that humic substances (HS) play as promoters of plant growth. Three concentrations of HS were evaluated in 200 grams of soil. The fertilizer (urea 0.3%) and humic acid in concentrations of 0.05%, 0.1%, and 0.2% were added directly and at the same time to the amount of soil, using a control sample without the addition of humic acid. Increase measurements were made at three-day intervals up to 45 days. Plants treated with high concentrations of HS demonstrated a significant increase in roots (p>0.05). In both plants, the concentration of 0.2% in HS showed the greatest increase in growth, with the melon plant showing the greatest variation as time passed, with its highest peak in 36 days (13.1 ± 0.05cm) of the experiment, while in the tomato plant the maximum growth occurred in 30 days (9.2 ± 0.01 cm). The Dunnett test showed that there was no statistically significant difference between the control and the concentrations of 0.05% and 0.1% (p>0.05), while among the control and the soil sample with a concentration of 0.2% there was a statistically significant difference (p<0.05). The results show a notable influence of humic acid on the growth of the studied plants, especially at high concentrations. Keywords: fertilizer, horticulture, humic acid, soils.