Optimizing processing tomato yield and quality in arid saline-alkali fields through appropriate fulvic acid application combined with aerated irrigation: regulate water, salt, and gas environment and enhance photosynthetic capacity
摘要
Salinized soils in global arid and semi-arid regions exhibit poor water retention, salt accumulation, and poor air permeability, severely limiting agricultural sustainability. While fulvic acid as a bioactive soil amendment can alleviate salt stress, aerated irrigation has also been proven to be a technique to improve water permeability and air permeability through gas-liquid two-phase regulation, but their combined effects on saline soil moisture, salinity, oxygen, and temperature conditions, CO₂ emissions, and crop productivity remain unclear. Therefore, this study conducted a two-year field experiment in a saline-alkali land in the arid region of Northwest China in 2023 and 2024. A completely randomized design was used, four fulvic acid application levels (F0: 0 kg ha‒1, F1: 25 kg ha‒1, F2: 50 kg ha‒1, F3: 75 kg ha‒1) and two aeration methods (A0: non-aerated irrigation, A1: aerated irrigation) were set up. The results revealed that fulvic acid application significantly influenced soil properties and tomato growth, with an optimal level F2 identified. Key plant physiological parameters, including plant height (PH), leaf area index (LAI), aboveground biomass (AGB), photosynthetic capacity (Pn), and chlorophyll content (Chl), which achieved their highest measurements during the growing season at the F2 level. Similarly, the final yield (FY), fruit quality, and water use efficiency (WUE) peaked at the F2 level, and then declined with further fulvic acid application. Soil conditions followed a similar pattern, as soil water storage (SWS), temperature (ST), and water-filled pore space (WFPS) were also optimized at F2. In contrast, soil conductivity (EC) was minimized at the F2 level, before increasing again at higher application rates. Compared with non-aerated irrigation, aerated irrigation increased SWS, soil oxygen concentration (SOC), ST, WFPS, PH, LAI, AGB, Pn, Chl, FY, quality, and WUE, while reducing EC. It is worth noting that both practices, fulvic acid application and aerated irrigation, increased the soil CO2 cumulative emission (SCE). Structural equation modeling revealed that fulvic acid and aerated irrigation indirectly enhanced crop growth (PH, LAI, and AGB), photosynthesis (Pn and Chl), and productivity (yield, sugar-acid ratio, and WUE) mainly by regulating SWC, EC, SOC, and SCE. This study demonstrates that the optimal treatment was F2A1, and compared with F0A0 treatment, the fruit yield, sugar-acid ratio, and water use efficiency increased by 14.7 − 20.3%, 18.8 − 23.1% and 15.3 − 15.6%, respectively. However, the application rate of fulvic acid and the water-air ratio of aerated irrigation should still be appropriately adjusted according to the degree of drought and salinization of the soil in the planting area, to achieve a synergistic balance of stable yield and emission reduction while reducing the stress pressure of crops.