The agricultural productivity of farmland in Northeast China’s Liaohe Plain is restricted by the salinity and sodicity of the soils, which have additionally low organic matter content. In order to improve saline–sodic soils, organic amendments are frequently applied. Our objective was to clarify how different organic amendments affect the diversity and composition of soil microbes, as well as how these factors are related to crop yield. In 2020–2021, we conducted an experiment with different organic amendments. The treatments included the application of crop residue incorporation (SR), lignite humic acid (LHA; 6 ton/ha), or cow manure (FM; 30 ton/ha), and a control (CK). The results show that, compared with CK, the content of SOM in soil treated with organic amendments increased by 5.3–7.4 g/kg; the available potassium (AK) of the LHA treatment was significantly higher than that of the FM and SR treatments by 32.17 and 42.79 mg/kg, respectively; and the available phosphorus (AP) of the LHA treatment was significantly higher than that of the SR treatment by 7.19 mg/kg. The pH and EC_1:5 values of the LHA treatment were significantly lower than those of CK by 1.36 units and 0.2 mS/cm, respectively. The application of organic amendments and changes in environmental conditions also significantly affected community structure and increased soil microbial richness and diversity. SR treatment increased the abundance of Acidobacteria. Further FAPROTAX (Functional Annotation of Prokaryotic Taxa) analysis showed that organic amendments can increase the abundance of microbes involved in the carbon and nitrogen cycle processes, such as aerobic_ammonia_oxidation, aerobic_chemoheterotrophy, nitrification, etc., which increases the kernel number per row and increases crop yield. LHA can increase the microbial abundance of the nitrogen cycle and reduce soil carbon mineralization, while also increasing soil nutrients and crop yield. This study provides a comprehensive understanding of the application of organic amendments in saline–sodic cultivated land.

Four typical halophytic communities found in saline-sodic soil, including Phragmites australis, Suaeda glauca, Leymus chinensis, and Puccinellia parl, were investigated in this study. A comparison was made among the electrical conductivity (EC) value, pH value, soil organic carbon (SOC), and soil enzyme activity across various soil depths. The findings of this study indicate that the EC and pH levels of the soil at the 0–40 cm depth vary among the four communities, with Suaeda glauca having the highest values, followed by Puccinellia parl, Phragmites australis, and Leymus chinensis. The highest value of SOC among the four communities was observed in the Leymus chinensis community (0.85–0.94 g/kg), followed by the Phragmites australis community (0.50–0.77 g/kg), and the lowest levels were observed in the Puccinellia parl community (0.37–0.78 g/kg). As the soil depth increases, there is a decline in the amount of SOC. With an increase in soil depth, the content of SOC in the soil decreased, and the content of total nitrogen (TN) and the activity of six enzymes in the soil of each community increased. Furthermore, at the soil layer of 0–20 cm, the TN content in the soils was negatively correlated with pH and EC (p < 0.01), and so was the total phosphorus (TP). Additionally, the TP content is considerably positively connected with alkaline phosphatase (ALP) activity, whereas the TN content is significantly positively correlated with Soil Urease (S-UE) activity. Within the soil depth of 20–40 cm, the levels of TN, TP, and SOC exhibit a negative association with pH and EC. However, this link is weaker compared to that observed in the surface soil. A strong inverse correlation (p < 0.05) exists between the TP concentration and the ALP activity. The objective of this study was to investigate the use of halophytes in various saline-sodic soils for diverse avenues of restoration, and to establish a database on the role and efficacy of plant roots in enhancing saline-sodic soil.