The use of plant growth-promoting bacteria to maximize agricultural sustainability is becoming more widespread. For example, Azospirillum are associative bacteria that convert atmospheric nitrogen into a form useful to plants, reducing the need for synthetic fertilizers. While Azospirillum is conventionally applied to soil, its effectiveness in hydroponic systems is a point of interest as hydroponic agriculture is an effective and low-impact way to grow crops with just water and dissolved nutrients in the absence of soil. In this study, lettuce and soybean plants were grown hydroponically with and without the presence of Azospirillum. Following 7 weeks of growth, lettuce chlorophyll levels were higher in Azospirillum treated than untreated plants, however photosynthetic rates were unchanged. For both species, plants accumulated more total biomass when grown with Azospirillum. These results suggest a higher nitrogen availability for plants in hydroponic systems when Azospirillum is added. This study demonstrates that Azospirillum can promote plant growth in hydroponic systems as it has when applied to soil, which proposes an encouraging option for the future of agriculture.
