The study looked at how different fertilization methods affect crop yields and soil nutrient levels in North China. After 7 years of testing, they found that certain fertilizer combinations led to higher wheat and maize yields. Without nitrogen fertilizer, soil nitrogen levels dropped significantly. The best fertilizer combination for balanced soil nutrients was N2P1K2. Nitrogen was the most important nutrient for crop growth, followed by phosphorus and potassium. Overall, the study showed that proper fertilization can improve crop yields and maintain soil health for sustainable farming.