A combination of bentonite, biological substrate, and microbial products to enhance coral sand and influence the growth performance of heat-resistant mustard greens, Brassica juncea

Background. Coral sand along the coast of Vietnam presents several challenges for plant growth, including inadequate nutrition, poor moisture retention, and high salinity, which complicate the cultivation of vegetables and trees. Purpose. This study aims to address the challenge of enhancing coral sand by optimizing its physical and chemical properties, moisture retention, nutrient availability, and suitability for cultivation. Materials and methods. The quality of mixed substrates is assessed using standard methods in accordance with Vietnamese Standards. Collected data were analyzed using SPSS 22 statistical software (IBM, USA) and MS Excel 365 software (Windows, USA). Comparison of differences between experiments based on one-factor ANOVA analysis at 95% confidence level. Results. Results indicate that with the improved soil formulation incorporating adhesive additives, organic substrates, salt-tolerant polysaccharide membrane-forming microorganisms, and salt-tolerant beneficial microorganisms at varying concentrations, porosity has increased to 54.90%, nearly matching that of alluvial soil at 56.14%. Consequently, the remediation formulas proved to be effective in enhancing soil characteristics. A growth index monitoring test conducted on the heat-resistant vegetable Brassica juncea after 35 days of cultivation demonstrated that the selected soil improvement formula yielded growth and productivity comparable to the control sample of alluvial soil, with the number of leaves reaching 7-8, an average leaf area of approximately 20 dm² per plant, a harvested vegetable yield of 20 g per plant, and a SPAD index of 23.87. Conclusion. The effect of adding microbial preparations and bentonite to coral sand increases EC and post-harvest vegetable volume but is not significantly different from formulas without preparations and bentonite.