Aplicação de microalga Desmodesmus abundans como biofertilizante foliar em Glycine max

Abstract

Desmodesmus abundans L2B Bold have attracted interest from researchers and industries, due to its biomass being rich in lipids, sugars, proteins, amino acids and minerals, as well as having molecules such as phytohormones, presenting great potential for biotechnological application. Therefore, there is always an effort to search for low-cost and accessible culture medium, one of the ways being commercial fertilizer. In addition, the compounds contained in D. abundans L2B Bold biomass can be used as a biofertilizer, increasing crop production, such as soybeans. Thus, the objective of this study was to evaluate commercial fertilizer as an alternative and more accessible for the production of D. abundans L2B Bold biomass and to investigate the potential of its biomass applied via foliar as a biofertilizer in soybean crop. The experiment was divided into two steps, the first being a standard BG-11 media and the other commercial fertilizer (CF) were tested. The population, metabolic profile and photosynthetic pigments of the microalgae were determined. At final, the biomass was collected and dried to estimate the cost of producing 1 kg of dry biomass from the two-culture media. The contents of photosynthetic pigments were lower in cultivation in CF, in relation to BG-11. The population and dry biomass of D. abundans L2B Bold were similar in both culture media. The identified intracellular metabolites induced differences in the cellular responses of the microalgae in the two-culture media. The use of commercial fertilizer reduced by 31.8% the cost of 1 kg of dry biomass, compared to standard BG-11 media. After, the second step, were tested, biomass concentrations (10, 20 and 30% v/v) of D. abundans L2B Bold with population 107 cells mL-1 grown in CF media and a control group (only water), foliar applied in soybean crop. Three sprayings were carried out, at 30, 50 and 70 days after sowing (DAS). The evaluation of plant height and stem diameter was performed after the first application of microalgal biomass, then every 15 days until 100 days after sowing (DAS). After 80 DAS, plants were collected to determine the leaf, stem and root dry masses of soybean plants, leaf nutrients were also quantified. Plant materials were collected after 48 hours of each application (32, 52 and 72 DAS) to quantify the photosynthetic pigment content leaves. At final, the plants were harvested to quantify grain yield and their minerals content. The application of 20% (v/v) of D. abundans L2B bold biomass positively influenced the stem diameter, in the leaf fresh and dry mass and stem dry, increased the number of legumes and grains, as well as, mass of grains per soybean plant. The application of microalgal biomass also increased the nitrogen and total protein content in soybean grains. Thus, these findings demonstrate that commercial fertilizer reduce the cost of obtaining D. abundans L2B Bold biomass and potentiate its application as a biofertilizer increasing the soybean yield.