Long-term balanced fertilization with a combination of inorganic and organic fertilizers improves soil nitrogen fertility in reddish paddy soil for double rice-cropping systems. Unbalanced fertilization can lead to decreased nitrogen content in the soil. Applying nitrogen, phosphorus, and potassium fertilizers together significantly increases nitrogen levels in the soil. Combining inorganic and organic fertilizers enhances soil nitrogen fertility compared to using only inorganic fertilizers. This balanced fertilization approach is effective for ensuring high and stable rice crop yields and promoting agricultural sustainability.