**5. Conclusions**

Compared to broadcasting fertilizer treatment, mechanized deep N fertilization enhanced rice growth under mechanical pot-seedling transplanting (PST) in terms of leaf area index and total above-ground biomass. Mechanized deep N fertilization also improved the grain yield, nitrogen use efficiency, and antioxidant enzyme activities in PST. Therefore, mechanized deep fertilization in mechanical pot-seedling transplanting should be recommended in actual production.

**Author Contributions:** Conceptualization, S.P. and X.T.; Methodology, S.P. and X.T.; Data curation, H.T., Z.W., M.D., and S.W.; Formal analysis, L.L., H.T., Z.Z., and M.D.; Project administration, S.W., Z.W., and Z.Z.; Supervision, L.L., H.T., S.P., and X.T.; Validation, L.L., H.T., Z.M., M.D, and U.A.; Writing—original draft, L.L., H.T., Z.M., and M.D.; Writing—review and editing, L.L., H.T., Z.M., M.D., U.A., Z.W., S.P., and X.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was supported by Key-Area Research and Development Program of Guangdong Province (No.2019 B020221003) and National Natural Science Foundation of China (31471442).

**Acknowledgments:** We thank Leilei Kong who provided the rice cultivars. The research was supported by Key-Area Research and Development Program of Guangdong Province (No. 2019 B020221003) and National Natural Science Foundation of China (31471442).

**Conflicts of Interest:** The authors declare no conflict of interest.
