The application of a biostimulant based on Ascophyllum nodosum, fulvic acid and nutrients mitigates water deficit in soybean

This study was intended to assess the effects of a biostimulant based on Ascophyllum nodosum and fulvic acid in the mitigation of water deficit in soybean plants. The experimental design was completely randomized in a 2 x 4 + 1 factorial scheme (two application times, four proportions of biostimulant, and a control. 65 days after sowing, plant height, stem diameter, number of leaves, leaf area, gas exchange, photosynthetic pigments, membrane damage, and dry masses were measured. The proportion of 0.250 kg ha-1 before the imposition of water deficit positively increased growth, gas exchange variables, and the relative chlorophyll index (p < 0.05). Leaf water potential was less negative (p < 0.05) when applying the proportion of 0.100 kg ha-1 before or 0.250 kg ha-1 after water deficit. The damage was reduced when 0.250 to 0.500 kg ha-1 was applied before the imposition of water deficit (p < 0.05). The biostimulant mitigated the effects of water stress on soybean, mainly when applied before the imposition of stress