Topographic classification of Chinese provinces.

Reducing fertilizer usage is a crucial measure for achieving high-quality development in Chinese agriculture. Utilizing panel data from 31 Chinese provinces spanning from 2004 to 2019, this study empirically analyzes the dynamic relationship between fertilizer application and grain production, exploring the underlying mechanisms. The study findings reveal that the application of fertilizers maintains a positive impact on grain production. The two variables will demonstrate a dynamic alternation between "strong decoupling" and "retreat decoupling," suggesting that grain production may either increase or gradually decline, while fertilizer application exhibits a decreasing trend. Mechanism analysis reveals a distinct substitution relationship between fertilizer use efficiency and application quantity. Increasing fertilizer use efficiency while reducing application quantity still facilitates the stable and increased production of grains. Heterogeneity analysis indicates that the efficiency of fertilizer use has a more pronounced impact on grain yield in the eastern and western regions. Increasing fertilizer quantity is detrimental to wheat yield but has a promoting effect on corn yield. However, in the main grain-producing areas, increasing fertilizer quantity can enhance wheat yield but is unfavorable for the overall grain yield. Additionally, nitrogen fertilizer input has exceeded the optimal level compared to potassium fertilizer. Continuously increasing nitrogen fertilizer input will hinder the increase in grain yield. Therefore, there is a need to shift from the notion of "more fertilizer is better" and focus on improving fertilizer use efficiency to transition from the emphasis on "quantity" to "quality" of fertilizer application.

减施化肥是推动中国农业实现高质量发展的关键举措。本研究采用2004—2019年中国31个省份的面板数据（panel data），实证剖析了化肥施用与粮食生产间的动态关联，并探究了其内在作用机制。研究结果显示，化肥施用对粮食生产仍存在正向影响。二者的动态关系会在“强脱钩”与“衰退脱钩”之间交替更迭，这意味着粮食生产可能出现增长或逐步下滑，而化肥施用量则呈现持续下降态势。机制分析结果表明，肥料利用效率与施用总量之间存在显著的替代关系：在提升肥料利用效率的同时降低施用量，仍可助力粮食生产实现稳定增产。异质性分析显示，肥料利用效率对东部和西部地区的粮食单产影响更为突出。增加化肥施用量会抑制小麦产量，但对玉米产量具有促进作用。不过在粮食主产区，增加化肥施用量虽可提升小麦产量，却不利于整体粮食总产的提升。此外，相较钾肥，氮肥投入已超出最优水平，持续增加氮肥投入会阻碍粮食产量的增长。因此，亟需摒弃“化肥越多越好”的传统观念，聚焦提升肥料利用效率，推动化肥施用从“重数量”向“重质量”转型。