Productivity of lettuce (Lactuca sativa L.) in response to the application of humic acids and diazotrophic bacteria, under field conditions

ABSTRACT Lettuce is one of the most consumed leafy vegetables in Brazil, generating great demand for its cultivation. It demands nutrients and a soil rich in organic matter to achieve high productivity, requiring large doses of organic compounds, leading to high production costs. Humic acids (HA) and diazotrophic bacteria (B) contain plant hormones, such as auxins, which promote cell elongation and increase of roots and absorption of nutrients, leading to plant growth and development. Due to these characteristics, they can be used as biostimulants in promoting lettuce productivity. The objective of this work was to evaluate the productivity of lettuce in response to the application of humic acids and diazotrophic bacteria under field conditions. The humic acids were isolated from bovine manure and the bacteria originated from the collection of bacteria from the Floriculture Sector of the Federal University of Viçosa - Campus Florestal, extracted from Cymbidium sp. orchids. The experiment was carried out in field conditions with cv. Vanda and the treatments were control (producer’s conventional cultivation), isolated applications of humic acid and bacterium, and combined application of humic acid + bacterium. A randomized block design with five replications was used. The application of biostimulants was carried out shortly after transplanting. Plant attributes of the aerial parts were evaluated. It was concluded that the treatments used, mainly the HA + B combination, increased lettuce productivity.