A new method was developed to study how fertilization affects maize yield over time. The researchers tested this method on maize hybrids from 1989 to 1994. They found that fertilization efficiency increased with better weather conditions, reaching a peak yield of 13-14 t/ha. In unfavorable weather, fertilization had little effect and could even decrease yield. The amount of fertilizer applied and the characteristics of the hybrid influenced the results. Increasing fertilizer dosage also increased efficiency.