One of the challenges of acidic sulfate soil is the high iron content in the soil, thus effective processing is needed to address iron toxicity.The purpose of this study is to determine the changes in soil pH, iron solubility, and organic C from liquid fertilizer in acidic sulfate soil in Danda Jaya Village, as well as to determine the strength of the relationship (correlation) and the form of the relationship between soluble Fe and soil pH, organic C and soil pH, and soluble Fe based on correlation and regression tests. This research is structured using a descriptive method by comparing the application of liquid fertilizer with a control. The study was conducted in the Chemistry, Physics, and Biology Laboratory of the Soil Department, Faculty of Agriculture, Lambung Mangkurat University. The results of the study indicate that the application of liquid fertilizer is able to increase pH and organic C and decrease iron solubility in acidic sulfate soil. Additionally, there is a correlation between soluble Fe and pH with a correlation coefficient of -0,95, a correlation between organic C and pH with a correlation coefficient of 0,91, and a correlation between organic C and soluble Fe with a correlation coefficient of -0,89. Furthermore, there are equations for the relationships: soil pH = -0,002 Soluble Fe + 5,958, soil pH = 0,30 organic C + 4,43, and soluble Fe = -154,92 organic C + 830,15.