To better understand the mechanism of nitrogen (N) distribution, absorption, utilization and loss in fertilizer under different tillage practices, a study was conducted to quantitatively explore the fate of fertilizer N in the soil–plant–atmosphere using the ¹⁵N labelling technique under the long-term conservation tillage experiment in Northeast China. The test crop used was corn. This study compared the residual amount of ¹⁵N fertilizer in soil, the content of ¹⁵N fertilizer N in particle organic nitrogen (PON), light fraction organic matter nitrogen (LFOMN) and heavy fraction organic matter N (HFOMN) under different tillage practices. In addition, N uptake, utilization and distribution by corn, the emission of N₂O and the gas loss of fertilizer N, and the fertilizer N utilization rate were also taken into account. The results showed that no tillage (NT) had a significantly lower amount of residual ¹⁵N fertilizer than a moldboard plow (MP) (p < 0.05). In general, the content under NT at the 0–30 cm soil layer was 7.85% lower than that of MP. NT led to significantly greater PON and LFOMN of soil organic N compared to MP (p < 0.05). ¹⁵N from N uptake, fertilizer absorption and utilization under NT were significantly higher than that under MP (p < 0.05), the soil N absorbed by plants under NT or MP was greater than 70%. The distribution of ¹⁵N from N fertilizer in each corn part increases in this order: seed > leave > sheath > stem > bract > ear; about 57.91–64.92% of ¹⁵N is distributed in the grain. NT resulted in significantly lower average and cumulative N₂O emissions than those from MP based on the static closed chamber approach (p < 0.05). The average and cumulative emissions of soil fertilizer ¹⁵N-N₂O under MP were also significantly greater than that of NT. Among the N₂O emissions, 15.3% and 22.98% came from fertilizer N under NT and MP, respectively. On average, 0.1–0.16% of fertilizer N was lost in the form of N₂O. There was a significant difference in fertilizer utilization between NT and MP, and NT was 4.23% larger than MP (p < 0.05). These one year findings suggest that NT plays a positive role in improving the N absorption and utilization of fertilizer in a Chinese mollisol and long-term effects need to be further studied.

Ammonia (NH₃) emissions from fertilized cropland are influenced by conservation tillage practices, yet the underlying mechanisms remain insufficiently understood in the black soil region of northeastern China. In this study, field observations were conducted in a maize cropland to compare NH₃ volatilization under conventional tillage, no-tillage, and straw incorporating treatments following application of urea and slow-release fertilizer. Results showed that compared with conventional tillage, no-tillage-straw mulching (T1) and ridge tillage-straw mulching (T3) treatments significantly reduced soil temperature while increasing soil moisture and decreasing the estimated soil resistance to NH₃ transport. These changes were accompanied by higher NH₃ emission factors (EFs) in the T1 and T3 treatments, although differences in EFs among tillage treatments were not statistically significant. Compared with urea, slow-release fertilizer delayed the occurrence of peak NH₃ volatilization and reduced cumulative NH₃ emissions by approximately 54%. Notably, measurements under slow-release fertilizer application revealed that elevated NH₃ volatilization persisted for more than 40 days after fertilization, indicating that conventional monitoring periods may underestimate cumulative NH₃ losses in conservation tillage systems using slow-release fertilizers. Overall, conservation tillage substantially altered soil environmental conditions associated with NH₃ volatilization, while fertilizer types strongly influenced the temporal dynamics and magnitude of NH₃ emissions. These findings provide useful insights for improving NH₃ emission monitoring, process understanding, and inventory estimation in conservation tillage systems.