Nanobubble-Saturated Water in Soil–Plant Systems: Root-Zone Oxygenation, Chemical Responses, and Structural Stability

Nanobubble-saturated water (NBSW) has gained prominence in agricultural research due to its ability to affect root-zone oxygenation and soil–plant interactions. This review aimed to analyze the available research on the impacts of NBSW on soil moisture storage, percolation, electrical conductivity (EC), microbial activity, and soil structural dynamics across different gas types and soil textures. Therefore, a systematic literature search was carried out, and the retrieved publications were synthesized with keyword co-occurrence and bibliometric analysis. This review fills the gap in the literature by integrating findings on root-zone oxygenation, nutrient dynamics, and soil structural responses into a single framework. Research showed that NBSW may influence water partitioning by increasing evaporation and lowering percolation, leading to different vertical moisture gradients. However, the effects could be impacted by the soil texture, as finer textures retained more moisture, while coarser soils increased oxygen penetration and microbial stimulation. Furthermore, increased oxygen availability under NBSW further changed microbial community activity, which could impact soil CO2 emissions and nitrogen and phosphorus cycling. While repeated NBSW application may gradually increase soil compaction, particularly in finer-textured soils, overall, NBSW demonstrated versatile watering modifications that might influence soil physical, chemical, and biological processes. However, further research is needed to determine the appropriate gas types and application strategies for different soils under real field-scale agricultural conditions.