Indole-3-acetic acid (IAA) is one of the most physiologically active auxins produced by rhizobacteria and is potentially applied for agriculture. Two endophytic bacteria, VR2 and MG9, isolated from the root of Chrysopogon zizanioides (L.) collected at Cha-Am, and the leaf of Bruguiera cylindrica (L.) Blume collected from a mangrove forest at Ban Laem, Phetchaburi Province, Thailand, were taxonomic characterised based on their phenotypic characteristics and 16S rRNA gene analysis. Strain VR2 was closely related to Enterobacter hormaechei CIP 103441T (99.6% similarity), while strain MG9 was closely related to Bacillus aryabhattai B8W22T (99.9% similarity). Consequently, they were identified as Enterobacter hormaechei and Bacillus aryabhattai, respectively. The IAA production of VR2 and MG9 strains are determined and applied to rice seeds for their root and shoot germination. Strains VR2 and MG9 greatly produced a yield of IAA, 246.00 and 195.55 µg/mL in 1,000 µg/mL of L-tryptophan at pH 6 for 48 h. They showed no significant differences in IAA to root and shoot development. However, the bacterial IAA exhibited potential nearby synthetic IAA, which had a significant effect compared to the control. IAA produced from these two strains might preferably trim down the use of synthetic IAA and could contribute to sustainable agriculture.

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Various kinds of substrates have been widely used for vegetables grown in soilless culture systems. The use of biochar is getting a lot of attention. However, the ideal proportion of biochar in the substrates combined with the use of vermicompost for high yields has not been thoroughly studied. This study aimed to examine in the pot experiment the effect of a combination of rice husk biochar (15% and 30%) and vermicompost (50, 100, 150, 200, and 250 g per pot) in growing substrate on nutrient uptake and yield of green lettuce. The other components of the substrates were cocopeat and sand. The results showed that the 30% of rice husk biochar in the growing substrate resulted in a significantly higher uptake of N, P, and K in leaves compared to lower biochar content with an average increase of 52%, 67%, and 117%, respectively. Maximum total fresh weight of marketable yield was obtained with 30% of biochar and 250 g per pot vermicompost in the substrate.

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