The aim is to investigate the variations in total nitrogen and inorganic nitrogen (specifically ammonium nitrogen and nitrate nitrogen) in soils characterized by differing fertility levels when treated with varying dosages of pig manure, elucidating the impact of different application rates of pig manure on nitrogen content in soils with distinct fertility levels. Indoor soil culture experiments were conducted to assess low, medium and high fertility soils subjected to various rates of pig manure application. The results showed that the total nitrogen content in the soil increased in response to higher applications of pig manure. Notably, when a substantial amount of pig manure was applied to high-fertility soil, the ammonium nitrogen content reached its peak at 5.68 mg/kg. Conversely, in medium-fertility soil treated with a high quantity of pig manure, the nitrate nitrogen content was maximized at 23.32 mg/kg. This phenomenon can be attributed to the negatively charged nature of nitrate nitrogen, which was not retained by soil colloids; thus, elevated levels of nitrate nitrogen in the soil correspond to an increased risk of leaching. Therefore, it is evident that there is a significant positive correlation between the total nitrogen content and ammonium nitrogen content in the soil and the application rate of pig manure.ontent with the application rate of pig manure. Furthermore, the application of high quantities of pig manure to soils with moderate fertility levels is more likely to result in the loss of soil nitrate nitrogen. These findings suggested that, in practical agricultural production, the risk of agricultural non-point source pollution caused by the application of pig manure can be mitigated while still adhering to the maximum carrying capacity of pig manure on dry farmland, thereby achieving certain agricultural economic benefits.