Managing hydroponic lettuce with a nutrient solution enriched with biofertilizer can increase productivity and improve commercial product quality; however, few studies have addressed this topic. This study aimed to evaluate the effects of adding a biofertilizer to the nutrient solution of hydroponic lettuce grown in spring and winter. A randomized block experimental design was used with two nutritional treatments and two growing seasons, each with six replications. For nutrient supply, one treatment did not use biofertilizer, while the other included it. The biofertilizer is a compound based on fulvic acids, an amino acid complex, and alginic acid, applied at a dose of 1 liter per 1,000 liters of nutrient solution. The use of biofertilizer resulted in increases in red and green excitation fluorescence indices (SFR-R and SFR-G), total chlorophyll, flavonoids, and anthocyanins by 32.1%, 41.1%, 30.7%, 10.3%, and 3.5%, respectively, in the spring crop. For nitrogen balance in plants during spring cultivation, the use of biofertilizer promoted increases of 21.7% and 89.9% in red and green excitation nitrogen balance indices (NBI-G and NBI-R), respectively. The use of biofertilizer resulted in average gains, regardless of cultivation period, of 27.6% for root fresh mass, 74.0% for shoot fresh mass, and 11.7% for shoot diameter, as well as increases of 27.8% and 43.4% for stem diameter and number of leaves in spring cultivation. These positive effects indicate that the biofertilizer improves nutrient absorption and stress resistance, resulting in more robust plants with better commercial characteristics.

Alginic acid, Amino acids, Fulvic acids, Hydroponics, Lactuca sativa L.