IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 BOOK OF ABSTRACTS 150 Soil Organic Matter, Caustobiolites, and Biochar Thursday, 27 August 2026 / Hall B SL75 Organic Biostimulants: Analytical Methodology and Performance on Wheat L. Edwin Liem1, Tannis Serben2 1 Global Humic Products Ltd. 53323 RR232 Sherwood Park, AB, Canada T8A 4V2, eliem@global-humic.com 2 Global Humic Products Ltd. Organic biostimulants containing humic substances (HS) and alginic acid (AA) were evaluated in two separate studies. A laboratory study was completed to evaluate the analytical methodology to quantify AA contents in the products. A field study was conducted to evaluate the products’ performance on wheat. The analytical method was based on the color reaction from degradation of uronic acid with carbazole [1,2,3]; later adopted by the Spanish Ministry of Agriculture and Fisheries, Feed and Environment [4]. HS was found to react with carbazole [5] and therefore suspected of interfering with the AA analysis. In this current study, five products (containing HS, AA, and combined HS + AA) were quantified for AA. At lower concentrations, spectrophotometer readings showed a nonlinear pattern, producing inconsistent AA concentrations. Modification was made to this method by preparing multiple samples at different dilution factors to identify where the readings fell within the linear pattern. AA concentration was calculated as an average from data generated within this region. Consistent results were obtained for all products, having AA of 0.36 to 11.79% with coefficient of variations ranging from 5.9 to 20.2%. It was also found that HS interfered with the method producing false positive results. This inaccuracy could be corrected using their control products [6]. HS and AA were considered among seven types of biostimulants [7]. HS enhanced crop yields or maintained them at reduced nutrients input [8]. AA improved plant growth and yields [9,10]. Combined HA and AA produced synergetic effects for the better enhancement of crop growth and yields [11,12]. In this current study, wheat was grown in outdoor test plots. Two products (containing HS and combined HS + AA) were applied on soil after seeding. HS biostimulant produced higher yields (up to 15% over control, at 3.8 L/ha rate). HS + AA biostimulant produced better yields (up to 17% over control, at 3.8 L/ha rate). Higher application rates did not produce better results. Both products did not improve protein contents of the harvested wheat, except at 3.8 L/ha of HS + AA biostimulant (2% over control).
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