Accelerating Soil Nutrient Supply and Enhancing Tomato Antioxidant System and Yield via Bacillus subtilis ‐Assisted Micro‐Nano Bubble Irrigation

While micro‐nano bubble irrigation (MNBI) and Bacillus subtilis offer significant benefits for improving soil conditions and enhancing crop yields, their combined effects remain unclear. This two‐year greenhouse study examined the combined effects of MNBI and Bacillus subtilis on soil enzyme activity, nutrient cycling, antioxidant system, yield, and economic benefits in tomatoes. Five treatments were established: subsurface drip irrigation (CK), MNBI (B0F1), and Bacillus subtilis applications with fertilizer rates at 100% (B1F1), 85% (B1F2), and 70% (B1F3) of the conventional rate. Results showed MNBI significantly increased soil enzyme activity, elevating soil urease, alkaline phosphatase, and catalase activity, which led to a rise in available nitrogen and phosphorus from 2022 to 2023. The application of Bacillus subtilis further enhanced these effects, with the B1F1 treatment demonstrating the highest soil enzyme activity and nutrient availability. Antioxidant enzyme activities (SOD, POD, CAT) significantly improved, while MDA levels decreased, indicating a strengthened antioxidant capacity in tomatoes. Dry matter (DM) and yield assessments showed that B1F1 increased DM by 8.1%–11.9% relative to the CK. B1F2 achieved yields comparable to B1F1 and showed the highest fertilizer use efficiency (FUE). Economic analysis revealed that B1F2 generated net profits of $20,035.50/ha, with a 230.1% return on investment, surpassing other treatments. The study concludes that combining MNBI with Bacillus subtilis optimizes the soil microenvironment and nutrient cycling, significantly boosting tomato yield and economic returns. The optimal combination was MNBI with Bacillus subtilis and 85% fertilizer application (B1F2), which maintained yields cost‐effectively.