Application of nitrogen-fixing purple non-sulfur bacteria in improving nitrogen uptake, growth, and yield of rice grown on extremely saline soil under greenhouse conditions

Abstract Highly saline soils negatively affect crop growth, especially rice. Although chemical approaches can be used, they damage the environment and the sustainability of the agriculture. Thus, a biological candidate should be assessed. Therefore, the study evaluated the impact of nitrogen (N)-fixing purple non-sulfur bacteria (PNSB) strains on improving soil properties, nutrient uptake, growth, and rice yield on highly saline soil in My Xuyen district, Soc Trang province. The N-fixing PNSB were hypothesized to boost soil nutrient availability and reduce soil salinity, leading to a greater rice growth and yield. A pot experiment was arranged in a completely randomized block design with two factors, including four N applying rates (100, 75, 50, and 0%) and N-fixing PNSB Rhodobacter sphaeroides (no added bacteria, single bacterial strain R. sphaeroides S01, single bacterial strain R. sphaeroides S06, and a mixture of two bacterial strains R. sphaeroides S01 and S06). The results showed that adding single strains S01, S06, and mixed strains S01 and S06 improved plant height by 4.02–10.4% (the first season) and 3.86–6.84% (the second season). Under the application of the mixture of two strains S01 and S06, the soil NH 4 + increased by 31.8–50.5%, while the soil Na + decreased by 16.0–25.7% in both seasons. From there, the total N uptake was also improved by 34.9–73.8% and the total Na uptake went down by 19.1–26.5% via two seasons. This led to greater rice growth and yield traits, such as the number of panicles per pot, the number of seeds per panicle, and the filled seed rate in both seasons. Ultimately, the rice grain yield was improved by 10.2–14.8% by the N-fixing PNSB under greenhouse condition. In conclusion, the current study successfully provided a potent N-fixer as a candidate for improvements of saline rice growth and soil health. Thus, this liquid biofertilizer should be further tested under field trails.