Impact of Aerated Drip Irrigation and Nitrogen Application on Soil Properties, Soil Bacterial Communities and Agronomic Traits of Cucumber in a Greenhouse System

Root hypoxia stress and soil nutrient turnover have been related to reduced crop productivity. Aerated drip irrigation (ADI) can effectively enhance crop productivity and yield. However, the response of the soil bacterial community to different irrigation water dissolved oxygen (DO) concentrations remains elusive due to the extreme sensitivity of microorganisms to environmental variations. We investigated the effects of aerated irrigation with different concentrations of DO on soil properties and agronomic performance of cucumber, as well as the contribution of the bacterial community. We performed experiments on cucumber cultivation in Shouguang, China, including different irrigation methods (ADI: O2–10 and O3–20 mg L−1, non-aerated groundwater: O1–5 mg L−1) and nitrogen (N) application rates: 240 and 360 kg N ha−1. ADI (particularly O2) significantly improved soil properties, root growth, cucumber yields, and irrigation water use efficiency (IWUE), and appropriate DO concentrations reduced N fertilizer application and increased crop yields. Furthermore, these changes were associated with bacterial community diversity, aerobic bacteria abundance, and consolidated bacterial population stability within the network module. Environmental factors such as soil respiration rate (Rs), DO, and NO3−-N have significant effects on bacterial communities. The FAPROTAX results demonstrated enhanced nitrification (Nitrospira) and aerobic nitrite oxidation by soil bacteria under ADI, promoting the accumulation of effective soil N and improved soil fertility and crop yield. Appropriate DO concentration is conducive to the involvement of soil bacterial communities in regulating soil properties and cucumber growth performance, which are vital for the sustainable development of facility agriculture.