【Objective】 Ammoniation is the process by which microorganisms convert organic nitrogen into inorganic nitrogen, which can improve soil nitrogen supply. Under different long-term fertilizer application scenarios, soil organic nitrogen undergoes significant changes, which makes comprehension of its ammonification process challenging. 【Method】 This study relied on a 29-year long-term targeted fertilization experiment at Shenyang Agricultural University, targeting four different fertilization treatments, including no fertilization (CK), chemical fertilizer (HCF), chemical fertilizer reduction (LCF), and fertilizer reduction combined with organic fertilizer (CMF), considering three soil depths (0-20 cm, 20-40 cm, and 40-60 cm), and three sampling period (pre-planting, maize tasseling stage and post-harvest). Using the real-time fluorescence quantitative PCR (qPCR) method, the abundance, activity, and nitrogen mineralization changes of soil ammonification gene gdh in different soil layers were studied during maize growth period after long-term different fertilization treatments. Also, the effects of fertilization, season, soil depth, and their interactions on ammonifier and soil net nitrogen mineralization rate were evaluated. 【Result】 The results showed that: 1) Compared with soil layer and fertilization treatment, the sampling period had the most significant impact on the abundance and activity of gdh genes. During the three sampling periods, the soil gdh gene activity and net nitrogen mineralization rate during the maize tasseling stage were significantly higher than pre-planting and post-harvest (P < 0.05) ; 2) Compared with no fertilization (CK), long-term application of chemical fertilizers (LCF and HCF) significantly increased soil nitrogen mineralization rate during the tasseling period (P < 0.05) while reduction of fertilizer combined with organic fertilizer (CMF) showed stable or increased soil nitrogen mineralization rate in post-harvest; 3) The abundance and activity of ammonifiers were significantly positively correlated with soil net nitrogen mineralization rate, and the ammonium nitrate ratio was an important factor affecting ammonifiers (P < 0.01). 【Conclusion】 In summary, nitrogen application, and crop absorption change the soil ammonium nitrate ratio, causing differences in the abundance and activity of soil ammonifiers. This led to changes in soil nitrogen mineralization rate. Long-term application of LCF and HCF is beneficial for increasing the rate of surface soil nitrogen mineralization in pre-planting and tasseling. CMF can help stabilize the activity of soil ammonifiers in post-harvest and promote the ammonification process of soil organic nitrogen.