# Progress and Prospect of Saline-Alkaline Soil Management Technology: A Review
## 4 The New Method of Treating Saline-Alkaline Soil Mainly with Wood Vinegar
### The Operational Principles of Wood Vinegar on Saline-Alkaline Soil  
Because wood vinegar contains numerous types of organic compounds, including phenols, alcohols, esters, and other small organic molecular substances [137; 138], it can regulate soil pH, increase root activity, promote seed germination and root growth, and shows potential for improving saline-alkaline soils [139]. A Study by [PERSON] et al. suggested that moderate use of wood vinegar could promote soil leaching [140]. This idea was also confirmed in the study by [PERSON] et al. [141], which showed that the combination of wood vinegar solution and biochar significantly improved the properties of saline-alkaline soil, increased soil nutrient content, and enhanced stress resistance and photosynthetic capacity of cotton. In addition, wood vinegar can promote an increase in  
Figure 5: Schematic diagram of the exchange process between acetic acid in wood vinegar and sodium ions in soil and their synergistic effects: This figure illustrates the exchange process between acetic acid in wood vinegar and sodium ions in the soil. After the exchange, some of the sodium ions are adsorbed by biochar, reducing the soil salinity. Meanwhile, acetic acid participates in improving the soil structure, ultimately promoting crop growth. This process reflects the synergistic mechanism of wood vinegar and biochar in the management of saline-alkaline soils. the soil microbial population, improve soil microbial structure, and has a positive effect on saline-alkaline land improvement [142]. It is also necessary to maintain a suitable concentration range for wood vinegar to improve saline-alkaline land. The appropriate dilution concentration is very important for improving saline-alkaline soil. Wood vinegar with too low a concentration cannot effectively improve the soil, while wood vinegar with too high a concentration may lead to salt accumulation and root toxicity. The results in a study by [PERSON] et al. [143] showed that different concentrations of wood vinegar notably influenced the acidity levels and electrical conductivity, and wood vinegar diluted 20 times could significantly decrease the soil's alkalinity, enhance its conductivity, and improving its enzyme activity. [PERSON] et al. also studied the effects of wood vinegar solution on soil properties and microbial activity at different concentrations. They found that wood vinegar solution diluted 10-100 times could be used for soil treatment, effectively enhancing soil conditions and promoting biological activity. At the same time, the specific dilution ratio needs to be adjusted according to soil conditions, crop species, growth needs, and other factors [114]. Wood vinegar is frequently utilized in conjunction with biochar to enhance soil properties. For instance, its co-application with biochar has been shown to augment blueberry yield in cropland soil and foster an increase in the population of fungi, Actinomycetes, and bacteria within the soil [144]. When applied in suitable concentrations, wood vinegar has been shown to markedly improve the physical and chemical properties of soils affected by high levels of salt and alkali as seen in Figure 6 below. This application boosts microbial populations and enhances enzymatic functions within the soil, leading to improved fertility and productivity in saline-alkaline soil conditions. In particular, wood vinegar can promote the number of fungi, Actinomycetes, and bacteria present inside the soil, enhance soil enzyme activity, and exert a beneficial influence on enzyme activity in soil under salt alkali stress [145]. For example, in northwestern Liaoning province, wood vinegar at 0.30% and 0.15% concentrations had the best effects on enzyme activity in low and medium fertility soils, respectively [146]. However, the concentration at which wood vinegar is applied needs to be carefully controlled to avoid excessive concentrations that inhibit microbial growth or cause competition between plants and microbes for nutrients in the soil [147].