This article analyzed the logic of reducing application of fertilizer under the constraint of plot scale based on the theory of induced technological change. The data about maize farmers in seven provinces of China obtained from 2020 China Rural Revitalization Survey （CRRS） and the 2SLS model were used to analyze the impact of plot size on fertilizer input. The results of empirical studies showed that expanding the plot scale reduced the input intensity of fertilizer and improved the input efficiency of fertilizer. The results of heterogeneity analyses showed that the expansion of plot scale by large-scale farmers had a greater impact on reducing application of fertilizer compared with small-scale farmers. The impact of expanding plot scale on fertilizer input was even more pronounced in term of farmers with higher input intensity and lower input efficiency of fertilizer. The results of analyzing mechanism showed that replacing agricultural labor with mechanical operations was a mechanism for reducing the expansion of plot scale and promoting the reduced application of fertilizer.