Fluvo-aquic soils in North China Plain were studied to understand their acidity and sensitivity to acidification due to intensive farming. The soil pH was found to be closely linked to nitrate levels, indicating that excessive nitrogen fertilizer use is a key factor in soil pH decline. Soils with lower calcium carbonate (CaCO3) levels were more sensitive to acid input, leading to a faster drop in pH. On the other hand, soils with higher CaCO3 were less affected by acid input. The study showed that the depletion of soil carbonates caused by intensive farming practices can result in a quicker decrease in soil pH, posing risks to soil quality and environmental health. It is crucial to improve methods for assessing acidification sensitivity in these soils to better manage their acidity levels.