Synergistic regulation of humic acid and aeration: Enhancing yield of processing tomato by improving soil environment under water-saving mulched drip irrigation

Mulched drip irrigation has been proven to reduce irrigation water usage while significantly increasing crop yields. However, its long-term application poses a potential risk of soil quality degradation. Therefore, achieving the synergistic regulation of water, fertilizer, and aeration through drip irrigation is crucial for improving soil quality and environmental conditions, thereby enhancing crop productivity. To investigate the synergistic regulation of humic acid and aeration on soil quality and their impact on processing tomato yield, a field experiment was conducted in Xinjiang, a region in China with arid conditions, in 2023 and 2024. The study employed urea as the nitrogen fertilizer and assessed the combined effects of three humic acid additions (H1: 0 %, H2: 0.25 %, H3: 0.5 %) and three aeration methods (A1: Ungassed, 5 mg/L; A2: Micro-nano aerated, 18 mg/L; A3: Venturi aeration, 9 mg/L) under 450 mm irrigation amount. Results showed that the synergistic regulation of humic acid and aeration significantly enhanced soil nutrient indicators. Compared to the conventional treatment (H1A1), the addition of 0.5 % humic acid under micro-nano aeration (H3A2) significantly increased soil NH4+ -N (46.21–51.49 %), TN (47.07–47.42 %), and TC (18.72–21.79 %). The activities of soil catalase (CAT, 9.91–14.29 %), nitrate reductase (NR, 9.98–15.54 %), sucrase (27.35–28.19 %), and urease (1.72–13.31 %) were all significantly improved. Moreover, the abundance of dominant bacterial and fungal species was notably increased. RDA analysis was used to identify the key soil environmental factors influencing soil bacteria (NH4+-N, NO3⁻-N, TC, NR, and Sucrase) and fungi (NH4+-N, NO3⁻-N, TC, NR, and CAT). Structural equation modeling (SEM) analysis of these indicators revealed the impact pathways of humic acid and aeration on bacteria and fungi. Both humic acid and aeration had a positive effect on bacteria (0.815 and 0.068) and fungi (0.481 and 0.251). Correlation analysis indicated that the key environmental factors influencing yield improvement were Actinobacteriota (bacteria phylum level), Dothideomycetes (fungi class level), and TC. The highest yield of 313.92 t/ha was achieved with the H3A2. The soil quality index (SQI) analysis revealed that H3A2 yielded the highest SQI. Additionally, model fitting indicated that H3A2 synergistically improved both soil quality and processing tomato yield. These findings provide valuable new insights into the development of sustainable agricultural production in arid regions, particularly regarding the effects of integrated water-fertilizer-aeration management strategies on soil nutrients, the soil microenvironment, and processing tomato yield.