This study was conducted to determine the effects of plant growth-promoting rhizobacteria (PGPRs) on growth, root system development, nutrient absorption, and expression of genes related to root development in rice seedlings. Bacillus pumilus TUAT1, a beneficial PGPR bacterium that is used as a component of commercially available biofertilizer, was inoculated onto rice seedlings once weekly for 3 weeks, and effects on growth parameters were determined. Our results showed that inoculation of B. pumilus TUAT1 spores at a density of 1 × 10⁷ colony-forming units (CFU) per mL yielded a significant increase in all traits compared to the control (water inoculum). In contrast, inoculation with vegetative cells did not yield significant effects (compared to control) in several traits, including the numbers of crown roots and lateral roots. CFUs increased with time and maintained to a higher number in the root zone than at the stem base of rice seedlings. Real-time quantitative reverse transcriptase-polymerase chain reaction of several genes known to be involved in root development revealed that B. pumilus TUAT1 inoculation led to increased accumulation of CRL5 transcripts and decreased accumulation of WOX11 transcripts in the basal stem, where crown root initiation occurs. Thus, our results suggest that spore inoculation of B. pumilus TUAT1 promotes rice crown root formation through suppression of cytokinin signal transduction by transcriptional control of CRL5 and WOX11. Consequently, the use of this bacterial strain may provide a means of improving growth, especially in root systems.

Durian is one of the most valuable and expensive fruits in Vietnam and Southeast Asia. Leaf nutritional disorders are considered to be causes of reductions in fruit yield and quality. However, studies on the nutritional balance in durian leaf are limited. In this study, we used the DRIS method for leaf limitation nutrient diagnosis at the stage 2 months before durian flowering. Our objectives were to (i) establish DRIS norms for the macronutrients (N, P, K, Ca, Mg, and S) in durian leaf and (ii) determine nutrient value ranges that are insufficient or excessive in durian production. A total of 180 leaf samples were collected and examined from 90 durian orchards cultivated on alluvial soils in the Vietnamese Mekong Delta. The results indicate that DRIS establishment for durian was highly reliable due to the significant positive correlation (r > 0.5) among nutrient indices. The limiting nutrients in durian leaf at the investigation stage were S, Mg, Ca, and P, where S and Mg were the most deficient. The optimal ranges of nutrients in durian leaf were determined and recommended in this study. Further studies are necessary to validate the efficiency of DRIS using nutrient omission trials under durian cultivation.

Uneven fruit ripening (UFR) is currently causing a decrease in the quality and value of “Ri 6” durian fruit. The soil moisture and nutrient (K, Ca, and Mg) levels present during the fruit development stage are the two main factors affecting UFR in durian fruit. However, measurements that can be used to determine the decrease in the UFR rate of durian remain unknown. Therefore, this study sought to evaluate the impact of plastic mulching (PM) and polyhalite fertilizer (PH) on improving the UFR rate and quality of durian fruit. A field study was conducted at three different durian orchards in the Vietnamese Mekong Delta (VMD) throughout two seasons (2022–2023 and 2023–2024). We used PM a month before fruit harvesting, combined with PH applied during the fruit development stage. Four treatments were used: (T1) control; (T2) PM, plastic mulching a month before durian fruit harvesting; (T3) PH, polyhalite fertilizer application (3 kg tree⁻¹ year⁻¹); and (T4) PM + PH, polyhalite fertilizer application (3 kg tree⁻¹ year⁻¹) and plastic mulching a month before durian fruit harvesting. The farmer’s fertilization practice (450 g N–450 g P–450 g K per tree⁻¹ during the fruit development period) was used in all treatments. Parameters such as soil physicochemical properties, fruit quality, and leaf mineral nutrient concentration were investigated at the harvesting stage. The results show that using PM + PH decreased soil moisture (>15%) but increased the concentrations of K, Mg, and Ca in both soil and durian leaves, thereby reducing the UFR rate (>80%) compared with the control. Additionally, applying PM + PH increased the aril proportion (>18%) and total soluble solids (approximately 5%) in durian fruit in comparison with the control. In conclusion, combining PM and PH improved the UFR rate and durian fruit quality. Therefore, we recommend that farmers apply these methods to their durian orchards to decrease physiological disorders and enhance fruit quality, thus contributing to achieving sustainable durian production in the VMD.

Background: Blueberries are ornamental plants grown in pots in many yards in the Mekong Delta (MD) region. In this region, the recent alluvial (RA) soil is fertile and ancient alluvial (AA) soil is considered degraded because it only has around a quarter of the nutrient content of the RA soil. Both soils have a high clay content, so organic matter is needed to improve their physical condition. This study aimed to identify the nutrients that limit the yield of blueberries in RA and AA soils of the MD. Methods: The pot experiment was performed using a factorial randomized block design (RBD) with two factors: (a) two soil types (RA and AA) and (b) four omission or treatment conditions (NPK, PK, NK, and NP). The same fertilizer formula was used for all treatments, including 45N–20P₂O₅–20K₂O and mixing CHC (10 tha^-1) into the potting soil. Results: The blueberry yield in AA soil was only 81% of that in RA soil. In both RA and AA soils, N omission caused foliar N content deficiency (10.42 g kg⁻¹), resulting in the content of foliar P (0.84 g kg⁻¹) and K (3.78 g kg⁻¹) to fall below the Trevett threshold. In both RA and AA, N omission resulted in reduced fruit yield (47% and 39%, respectively) as well as reduced weight of the stem (70% and 42%, respectively) and leaf (59% and 46%, respectively). Increased crop yields in soils were mainly related to nitrogen fertilizer. The indigenous nutrient supply (INS) of RA, which is fertile, was high but its apparent nutrient recovery efficiency (ARE) index was low, whereas the INS of AA, or the level of degraded soil, was low but its ARE index was high. In alluvial soils, the higher the INS level, the less positive the impact on the ARE index. In AA soil, the indigenous N and K supplies can be improved through fertilizer investment; however, a balance must be achieved considering economic efficiency.

The available phosphorus (P) in acid sulfate soils (ASSs) is low because of fixation by aluminum (Al) and iron (Fe), resulting in decreased P use efficiency and crop yield. At present, the use of dicarboxylic acid polymer (DCAP) coated on P fertilizer is expected to improve P use efficiency and plant productivity. However, the influence of DCAP on P solubility and on the yield of sweet potato cultivated in acidic soils has not been elucidated. Thus, the aimed of this study was to evaluate the effect of the use of DCAP-coated P fertilizer on the availability and nutrient uptake of P as well as the yield of sweet potato. Under the greenhouse condition, the use of DCAP significantly improved P availability (-3 mg P kg???1), increasing tuber diameter and length by-0.5 and-1.0 cm, respectively. Thus, the productivity of sweet potato in the treatment 40 -kg P2O5 and 60-kg P2O5 ha???1 coated with DCAP was higher by about 100 g pot???1 than that in the same rate of P fertilizers (40-and 60-kg P2O5 ha???1) not coated with DCAP. In the field experiment, P accumulation (82.7 kg P2O5 ha???1) and tuber yield (22.0 t ha???1) in the treatment of DCAP-coated with 60-kg P2O5 ha???1 were not significantly different compared with that in the treatment of 80-kg P2O5 ha???1 (82.1 kg P2O5 and 21.7 t ha???1, respectively). Furthermore, the use of DCAP combined with 75% P fertilizer increased the P availability by the same amount as that with the use of 100% P fertilizer. Hence, the use of DCAP reduced about 25% of the chemical P fertilizer applied in soil.