Synergism between humic biostimulants and mineral fertilizer stimulates lettuce productivity on a Ultisol

Resumo

Bioactive humic fractions have proved effective in improving the productivity of vegetable crops. We examined the effect of commercial biostimulants rich in humic (HA) and fulvic acids (FA) obtained from leonardite on agronomic efficiency and distribution of humic substances in soil bearing a lettuce crop. For this purpose, we conducted a greenhouse experiment by using 2.5 L pots containing Ultisol samples that were supplied with HA or FA rich commercial biostimulants. Humic products were used alone and in combination with NPK mineral fertilizer. The soil was subjected to the following treatments: Control (no fertilizer), HA, HA+NPK, NPK, FA and FA+NPK. Productivity was assessed from plant height and diameter, number of leaves, fresh and dry mass, and root length. Treatment FA + NPK provided the greatest values of the studied variables, namely: plant height of 15.2 cm, diameter of 34.7 cm, and 27.5 leaves per plant. This result is indicative of a synergistic effect of the humic biostimulant and inorganic fertilizer on lettuce growth and nutrient content.