Exploration of soil components on Na+ adsorption based on the long-term fertilization experiment

Soil was sampled from the Laiyang Long-Term Positioning Experiment Station at Qingdao Agricultural University (120°43'16" E, 36°59'16" N), and was classified as Ustic Cambosols. This region has a typical temperate continental monsoon climate, with an average annual temperature of 11.6 ℃ and annual precipitation of 655.6 mm. The fertiliser experiment commenced in 1978. Three soil samples from the CK, NPK, and M treatments were collected after the wheat harvest in 2023. After sampling, the visible gravel and biological residues were removed, and the soil was subsequently sieved to less than 2 mm.