A study in Funing County looked at how different types and amounts of fertilizer affect the yield of spring maize. They found that using chemical fertilizer increased yield by 11.0%-39.1%, with the best results seen with a specific ratio of N, P, and K. Adjusting fertilizer application based on soil fertility levels can further increase yield. In low-yield fields, more N, P, and K should be applied, while in high-yield fields, less K is needed. Using a combination of chemical and organic fertilizer, as well as formula fertilizer, can significantly boost yield by 35.9%.