Evaluation of the bio-stimulating potential of Chlorolobion lunulatum microalgae biomass compared to organic fertilizers on soybean growth and productivity

• Grant number: 24/06955-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date until: August 01, 2024
• End date until: July 31, 2025
• Field of knowledge: Biological Sciences - Botany - Pant Physiology
• Principal Investigator: Sarah Caroline Ribeiro de Souza
• Grantee: Natalia Ramires Pedroso
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil

Abstract

Soybean (Glycine max (L.) Merrill) plays a vital role in the national agricultural economy, standing out as the main oilseed and making Brazil the world leader in production and exportation. Despite its great relevance, the excessive use of mineral fertilizers in soybean cultivation poses significant risks to human health and the environment. Less aggressive alternatives, such as bovine manure and Bokashi, have already demonstrated their benefits in the consistent and sustainable development of the oilseed. However, the introduction of microalgae biomass as an agricultural biostimulant is an innovative approach that requires further analysis. This study aims to understand the effect of microalgae biomass on soybean growth and productivity, especially regarding nodulation and nitrogen fixation, comparing its performance with that of organic fertilizers. Conventional soybean seeds (cultivar BRS 284) and transgenic (RR) will be used, cultivated in corrected cerrado soil, and fertilized with dry biomass of the microalga Chlorolobion lunulatum, bovine manure, and Bokashi, alone and in combination. The plants will be grown in a greenhouse under natural light conditions and semi-controlled temperature, with humidity maintained between 50 and 60%, and regular irrigation. Plant collection will occur at two stages: V4 (vegetative stage with three expanded trifoliate leaves) and R5 (reproductive stage with pods), for growth, nodulation, and productivity analysis. We will evaluate total fresh and dry biomass, leaf volume and area, height, and the presence, quantity, and mass of nodules. Additionally, pods, seeds, and biomass will be quantified in R5, and macronutrient, micronutrient, total protein, free amino acid, and starch contents will be analyzed. Total proteins will be assayed in plant samples with 0.1 M NaOH extracts, using Bradford reagent and bovine serum albumin as a standard. For starch, seeds will be digested in 30% perchloric acid, and the resulting glucose will be quantified in a spectrophotometer. Free amino acids will be extracted in MCW and quantified with ninhydrin, using leucine as a standard. Distinct responses in soybean growth, productivity, and nodulation among different organic fertilizations are expected, as well as variations in nutrient distribution in the grains, depending on the genotype.