Page 422 - Demo

426 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGYthe rice straw composting process meets the quality standards outlined in the National Technical Regulation on fertilizer quality - QCVN 01-189:2019/BNNPTNT [15]. This result is also mentioned in some works of Nguyen Thu Ha et al. and Nguyen Van Thiet et al. (2015, 2022) [8,24]. However, for better soil improvement efficiency, organic fertilizers should be supplemented with some functional microorganisms to create microbial organic fertilizers, increasing the density of beneficial microorganisms, contributing to more effective soil improvement. Results show that after mixing microbial preparations with organic fertilizer products, two functional microbial groups suitable for straw treatment are the phosphorus-decomposing and cellulolytic microorganisms, with a density of over 106 CFU/g, meeting the quality standards for microbial organic fertilizers according to the regulations. The mixing ratios of sea sand and microbial organic fertilizer were tested in four formulas: Formula 1 (control): 30kg sea sand; Formula 2: 20 kg sea sand + 10 kg microbial organic fertilizer (2:1); Formula 3: 15 kg sea sand + 15 kg microbial organic fertilizer (1:1); Formula 4: 10 kg sea sand + 20 kg microbial organic fertilizer (1:2). These formulas were applied to three types of vegetables: tomato, water spinach, and green mustard. Research results indicate that the differences in yield-forming indicators across all three vegetable types are quite similar, with these indicators increasing gradually from formula 1 to formula 4. Notablya, the vegetable biomass of the mixing formulas increased compared to the control, ranging from over 2.57 times for formula 2 to over 3.4 times for formula 3 and formula 4. This result is particularly favorable for tomatoes, with the actual yield increasing up to 17.7 times compared to the control formula. This could be due to the increased addition of microbial organic fertilizer in each formula, providing abundant nutrients for the plants. However, after statistical processing, it can be seen that formula 3 and formula