The main aim of this study was to deal with isolation, characterization and identification IAA producing bacteria from paddy rice cultivated soil samples collected in rice–shrimp farming system in salt affected areas of the Mekong Delta of Vietnam. Fifteen soil samples collected from the rice crop in the rice-shrimp farming system of 5 different provinces within the Mekong Delta, Vietnam were used to isolate the IAA producing bacteria. NBRIP media was used to isolate the potentially IAA producing bacteria. Result showed that 213 isolates were obtained from the fifteen different soil samples. Out of 45 indole acetic acid producing isolates, ten were selected as efficient producers. One out of ten, the isolate ST2-1 was identified as the most promising strain as efficient biofertilizer inoculants to promote plant growth. This strain produced 33.13 mg.L^-1 as the highest concentration of IAA after 8 days of incubation. As well, this strain stimulated the growth of rice’s roots and dry biomass after 7 days of experiment with Hoagland medium containing 0.3% NaCl in 100 mL glass tube. This strain produced well IAA production in pH variation range of medium between 5 and 9 and this bacterial strain can resist to salinity of environment up to 3% NaCl. However, this bacterial was highly inhibited by not only 3 commonly used antibiotics: Ampicillin, Chloramphenicol and Steptomycin at recommended rates but also 3 plant pathology fungicides: Thiophanate Methyl, Propineb and Mancozed regarding to IAA production ability. The results of the 16S rRNA gene sequence analysis showed that this IAA producer coded as ST2-1 was genetically identified as species of Bacillus megaterium ST2-9 since 99% of its sequence affiliated with Bacillus megaterium. In conclusion, the study suggests the IAA producing bacteria as efficient biofertilizer inoculants to promote plant growth.

In the Vietnamese Mekong Delta, soil quality and crop yield are steadily declining under rice monocultures with three crops per year. The objective of this study was to evaluate the medium-term effects of rotating rice with upland crops and adding organic amendments on rice yield, and to relate this to soil quality. A field trial with split-plot design including two factors and three replicates was carried out from 2017 to 2020, over the course of nine consecutive cropping seasons. Crop rotations and organic amendments were applied as main-plot and subplot factors, respectively. The rotations were (1) rice–rice–rice (R–R–R), (2) soybean–rice–rice (So–R–R), and (3) sesame–rice–rice (Se–R–R), while organic amendment treatments included (i) no amendment (NO-AM), (ii) compost of rice straw and cow manure (RS+CM), and (iii) sugarcane compost (SGC); the composts were applied at a rate of 2.0 t ha⁻¹. The rotation cycle started with the so-called spring–summer (SS) season, followed by the summer–autumn (SA) season and ending with the winter–spring (WS) season. Rice yield significantly (p < 0.05) increased under organic amendments after nine growing seasons (2019–2020 WS), with an increment of 5.1% for RS+CM (7.07 ton/ha) and 6.1% for SGC (7.14 ton/ha). Contrary to our expectation, rotations with upland crops did not significantly increase rice yield. Rice yield significantly and positively correlated with an integrated soil quality index–SQI (r = 0.85) for the topsoil (0–15 cm), but not for the subsoil (15–30 cm). The increased availability of soil nutrients (Si and marginally also P) and improved soil physical properties probably induced by organic amendments, along with other soil properties under study, cumulatively attributed to enhanced rice yield. Repeated organic amendments thus becomes an effective management practice in improving soil quality under rice-based systems and could be applied to sustain rice yield in rice-producing regions with similar soil types and climatic conditions. Use of a SQI involving several soil quality indicators enables us to quantify the overall importance of soil fertility for rice yield versus other factors, and it provides an effective means of quantifying the integrated effect of improved management. Moreover, integrating a wide range of soil quality indicators in a SQI ensures its applicability across diverse settings, including different crop rotations and various soil types.

Introduction: Longan is a perennial crop and profitable export fruit well-suited to the Mekong Delta's climate and soils. Although soil deterioration in longan orchards has been studied, little research has addressed soil bacterial communities and their role in soil health. This study investigated the structure of soil bacterial communities and their associations with soil physicochemical properties in longan orchards.Methods: Soil samples were collected from longan orchards cultivated for 15 (N15), 20 (N20) and 30 years (N30) in Vinh Long Province, Vietnam. High-throughput sequencing of 16S rRNA amplicons was employed to assess bacterial diversity and community composition, followed by correlation analyses with soil properties.Results and Discussion: The dominant bacterial phyla identified across sites included Acidobacteria, Proteobacteria, Chloroflexi, Actinobacteria, and Bacteriodota. Bacterial abundance in these soils was positively correlated with sand, pH, NO₃^- and phosphate solubilizing microorganisms, and negatively correlated with moisture, silt, clay, NH₄⁺, exchangeable potassium and available manganese. Longan orchard soils from all three time periods (N15, N20, N30) had more microbial species in common, than in unique ways. However, time under cultivation was an important factor, with species diversity decreasing with age. The youngest orchards (N15) exhibited the highest number of soil bacterial diversity, followed by decreasing diversity as the orchards aged (N20) and lowest at 30 years (N30). Soil properties exhibited complex and interlinked relationships with soil bacterial phyla. Overall, long-term cultivation of longan orchard soil negatively impacted microbial diversity, potentially altering key properties of soil, hence underscoring the necessity for sustainable soil management to preserve soil health and production.

This article presents an environment monitoring model for agricultural production applied to farmers in the Mekong Delta, Viet Nam. The proposed model's special feature is a system combining techniques such as IoT, agent-based, sensor networks, and data warehouses. Successfully deploying the model in monitoring the water level, and the environmental factors of the rice soil such as NPK, pH, EC, temperature, and soil moisture not only aids managers and farmers monitor environmental quality indicators in real time, but also experts to analyze data, give warnings and appropriate response solutions in agricultural production according to the pivot strategy towards Agriculture 4.0 proposed by the Minister of the Ministry of Agriculture and Rural Development of Viet Nam.

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.