Isolated and combined application of bioinputs and humic and fulvic substances on lettuce crop performance

ABSTRACT This study aimed to evaluate the effects of isolated and combined applications of humic and fulvic substances and liquid bacterial inoculants on the agronomic development and productivity of lettuce varietal groups. Two greenhouse experiments were conducted simultaneously, one using crisphead lettuce and the other using loose-leaf lettuce, in a randomized blocks design with six treatments: T1: control (no application); T2: humic and fulvic substances + Bacillus megaterium and Bacillus subtilis; T3: B. megaterium and B. subtilis; T4: humic and fulvic substances + B. megaterium, B. subtilis, and Bacillus aryabhattai; T5: B. megaterium, B. subtilis, and B. aryabhattai; and T6: B. aryabhattai; with 18 replicates. Agronomic variables evaluated included stem diameter (SD), head height (HH), head diameter (HD), head circumference (HC), head fresh mass (HFM), and head dry mass (HDM). Foliar macro- and micronutrient accumulation were also assessed. Data were analyzed using multivariate statistical techniques. For both varietal groups, canonical discriminant analysis (CDA) indicated that treatments T3 and T6 were more closely associated to each other and with yield-related responses, such as SD, HH, HD, and HFM. Greater similarity was also observed between T1 and T5, which were generally associated with higher accumulations of S, Zn, N, B, and Fe. Principal component analysis (PCA) and hierarchical clustering identified three distinct groups: the first comprising T4, the second T2, and the third T1, T5, T3, and T6. Overall, multivariate analysis combined with box-and-whisker plots confirmed the superior performance of treatments T1, T3, T5, and T6 in both nutrient accumulation and plant development.