This study evaluated the effects of some environmental conditions on IAA biosynthesizing capacity of four nitrogen fixing bacteria, namely Paenibacillus cineris TP-1.4, Bacillus megaterium MQ-2.5, Klebsiella pneumoniae OM-17.2, and Pseudomonas boreopolis CP-18.2. Carbon source, pH, NaCl, and tryptophan supplement treatments were set to investigate the effects of those environmental factors on IAA synthesis. The IAA synthesizing capacity of bacterial strains in liquid medium was measured spectroscopically following incubation by Salkowski's reagent method. The results showed that, under the sucrose amendment, the IAA concentrations produced by all four bacterial strains were significantly higher than those of the other four carbon source added treatments. Two of the four bacterial strains produced the highest yield of IAA in liquid medium at pH 7 (TP-1.4 and OM-17.2), whereas pH 8 was optimum for the other two strains (MQ-2.5 and CP-18.2). The MQ-2.5 strain could synthesize IAA fairly well in up to 5% NaCl and produced the highest amount of IAA with 1% NaCl. Furthermore, IAA synthesizing capability of tested bacterial strains increased sharply along with increasing tryptophan content in culture medium except for the TP-1.4 strain. From the current study, these isolates emerged as possible alternatives for future IAA production for plant growth and yield enhancement. Hence, they have a great potential to be used as bio-inoculants for plant growth promotion in eco-friendly and sustainable agriculture.

This study assessed antagonistic capacity of various indigenous microorganisms (IMO) collected from different cropping systems within Soc Trang province against plant pathogenic fungus including Fusarium oxysporum and Rhizoctonia solani. Biocontrol activity of fifteen collected IMOs was investigated on PDA agar media for 5-7 days under laboratory conditions with three different scenarios. IMO and pathogenic fungus were incubated at the same time and IMO was introduced before and after inoculation of plant pathogenic fungus. The results illustrated that all surveyed IMOs were found to have highly potential biocontrol against two plant pathogenic fungi to different extents and IMOs which were introduced before the inoculation of pathogenic fungi showed the highest efficiency in biocontrol of plant pathogen. Particularly, four out of fifteen IMOs which were collected from bamboo, shallot, grapefruit and guava farms showed their highest antagonistic efficacy on Fusarium oxysporum biocontrol by completely decaying fungal hyphae of this fungal strain after seven incubation days. For Rhizoctonia solani, all IMOs displayed highly antagonistic ability with inhibitory percentages varying between 52.96% and 92.59% after two days. The antagonistic functions of all collected IMOs could be exploited for plant protection from plant-pathogenic fungus.

Indigenous microorganism (IMO) has great potential for agricultural uses since they have high ability in biodegradation, nitrogen fixation, phosphate solubilization, plant growth hormone production as well as bio-control. This study aimed to determine the presence of some different major groups of microbes in IMO from different agri-ecosystem habitats like bacteria, fungi, actinomyces, Salmonella, Shigella, E. coli, and Coliform. The presence of bacteria, actinomyces, and fungi of IMO samples was identified by 27F/1492R, 243F/1378R and ITS1F/ITS4R primers, respectively. Numbers of bacteria, fungi, and actinomyces were determined by the plate counting method on TSA, PDA and Starch media, respectively. The numbers of Salmonella sp. and Shigella sp. were determined by the plate counting method on selective Salmonella and Shigella agar (SS agar) after incubation for 48 hours at 37oC while the density of Coliforms sp. and E.coli were counted by the Most Probable Number method (MPN). The results of the study showed that 3 major groups of microbes including bacteria, fungi, and actinomyces in 14 collected IMO samples were detected genetically. Moreover, bacterial numbers were dominated and ranged from 106 to 109 cfu/g IMO samples while the density of fungi and actinomyces were lower and varied from 105 to 107 cfu/g IMO sample. Interestingly, all surveyed IMO samples did not contain any human disease pathogens such as Salmonella, Shigella, Coliforms and E. coli. These results imply that collected IMO contains a high diversity of major groups of microbes and can be used as safe bio-stimulants for clean vegetable production.

The objective of the study was to utilize the biogas effluents to produce solid and liquid organic fertilizers, as well as evaluate their effect on the growth and yield of corn and mung beans under field conditions. For liquid organic fertilizer, biogas effluents were mixed with fish emulsion and beneficial bacteria while biogas effluents-absorbing coal slag was mixed with sugarcane filter, fishmeal and beneficial bacteria to create solid organic fertilizer. Liquid organic fertilizer was irrigated with a dose of 5 L/1000 m2 while solid organic fertilizer was applied with a dose of 1 ton/ha with 75% recommended NPK formula for maize and mung bean. The results showed that applying solid or liquid organic fertilizer formulated from biogas effluents with other amendments helped to reduce the amount of recommended NPK fertilizer by 25%, but still maintained growth and yield of maize and mungbean equivalent to the control treatment fertilized with 100% recommended NPK. In conclusion, the amount of organic matter and N, P, K in biogas effluents from biogas digesters can be utilized to produce organic fertilizers which not only help to reduce chemical fertilizers, but also solve the environmental problems and create new friendly value-added products for practicing sustainable agricultural production.