【Objective】With increasing concerns about sustainability of agroecosystems, the practice of no-tillage in combination with crop straw/stalk mulching is getting widely used in China. In this scenario, large amounts of maize stalk were therefore left as mulch in the fields under a no-tillage cropping system. However, little is known about fate of the nitrogen (N) contained in the mulch of crop stalks in spite of the fact that they generally contain significant amounts of N. 【Method】Therefore, a four-year field-plot experiment was conducted to explore effects of mulching of maize stalk in fields in the agroecosystem of Northeast China on accumulative plant uptake, recovery and loss rate of the N contained in the maize stalk mulch over four experimental years. The experiment was designed to have two treatments. In Treatment T_S1, the plots were mulched with ¹⁵N-labelled maize stalk in the first year, and not with any in the following three years, while in Treatment T_S2the plots were mulched with ¹⁵N-labelled maize stalk in the first year, and with ordinary maize stalk in the following three years. 【Result】Results show that over the four experimental years, the two treatments did not vary much in accumulative yield of maize grain or stalk and total N uptake. However, in Treatment T_S1 about 14.2% and 6.7% of the N in the mulch was recovered by maize grain and stalk, respectively, and significantly higher than that (12.4% and 5.8%, respectively) in Treatment T_S2. Compared to the accumulative amount of N recovered from the mulch by crop, more of the N in the mulch was retained in the soil, especially in the top soil layer in both treatments. About 40.9% and 73.8% of the N in the mulch was retained in the soil (0 ~ 60 cm) in residue form and about 38.6% and 8.1% lost in Treatments T_S1and T_S2, respectively. Compared to Treatment TS1, Treatment TS2 was relatively higher in soil microbial biomass C and N, but lower in mineral N derived from the mulch, which indicates that continuously mulching the fields with crop stalk significantly increased the microbial retention rate of the N in the mulch, while decreasing the leaching risk of the N in the mulch in the soil-crop system. 【Conclusion】All the findings listed above suggest that long-term practice of no-tillage in combination with crop straw/stalk mulching can effectively enhance accumulation in the soil of the N brought in with mulching, which may have some significant implications for raising and maintaining the content and stability of soil N in crop fields.