Effect of Humic Acid on Growth and Productivity of Tomato Plants Under Heat Stress

The purpose of this study was to evaluate the effect of humic acid (HA) applied at 4.8, 9.6 and 14.4 kg·ha⁻¹ on the growth and productivity of two tomato hybrids Nema 1400 and Platinium 5043 under hot continental climate. HA was applied twice to soil: the first one – three weeks from transplanting and the second one, after one week from the first application, in both seasons. Application of HA during the summer season targeted a great results on tomato plant growth and productivity. HA at 14.4 kg·ha⁻¹ in-creased the vegetative growth of tomatoes (plant height and fresh weight) and flowering parameters (number of flower clusters and flowers per plant) as well as yield characters (fruit number per plant and fruit weight, which resulted in higher early and total yield) in both seasons. HA application had the least impact on fruit number per plant, and on vitamin C and total soluble solids (TSS) concentration as compared with control.