ISSN: 1659-2751



Efficiency of Application of Humic Substance Extracts from Vermicompost on Production of Lettuce and Pak Choy


Humic substances are used in agricultural production for various purposes, from inducing better rooting capacity of plants to increasing crop biomass and yields. Vermicompost has been suggested as a source for the extraction of humic substances; however, little information is available regarding the effectiveness of humic substance extracts from vermicompost on crop production. The effectiveness of foliar applications of a humic substance extract from vermicompost was evaluated in a greenhouse experiment. The experiment evaluated the effect of three foliar fertilizers, NPK, SH (humic substances), and SH+NPK (humic substances with NPK) and on the root and aerial dry biomass and on the foliar N, P and K concentrations of pak choy and lettuce. All foliar fertilizers were applied at concentrations of 1 %, 5 % and 10 %. At 42 days after planting, root and aerial dry biomass were quantified. The root and aerial biomass of pak choy and lettuce were significantly lower with SH than with NPK and SH+NPK. No significant differences in root and aerial biomass were found between equal concentrations of NPK and SH+NPK for both crops, but both biomasses significantly increased as concentrations of NPK and of SH+NPK increased. No significant differences were observed in foliar N, P and K concentrations among all three foliar fertilizers. The results of this study clearly indicate that the humic substance extract from vermicompost had no effect on the growth of either crop and that all growth was a result of the addition of NPK. The lack of effect of the humic substance extract was due possibly to very low or inexistent concentrations of humic substances in the extract, which might have resulted from the use of fresh vermicompost in which the appropriate humification processes had not occurred.

Key words: humic acid, biomass, lettuce, vermicompost, pak choy, humic substances.

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