农时视角下的小农机械化：对我国不同熟制地区粮食收获机械化的考察

长期以来经济学家认为农业机械可以大幅提高劳动生产率，但不能增加土地生产率或效果有限。农业工程专家相信其他环节机械化可以增产但收获环节除外，因为机收损失率难以做到比人工低。如果机收没有增产效果仅仅起到节省劳动作用，那么很难解释1990年代中后期我国农业劳动力仍普遍过剩的情况下，稻麦联合收割机在黄淮海平原多熟制地区迅速普及的现象。本研究从“抢农时”视角对此提出新的解释：机械收获在多熟制地区不仅可以替代劳动力，而且可以减少土地“闲置时间”，即农民可以晚收本茬或早种下茬作物、改种生育期长的高产作物与品种，因增加光合作用时间而增产。本研究通过实证分析农时紧张程度不同地区农民的收获机械采用行为的差异，以及实证分析收获机械推广对生育期长的高产作物与品种的种植决策的影响，来检验上述假说并测度增产贡献。研究结果有助于深化对于小农机械化的理解，为加快我国农业现代化、保证粮食安全的相关决策提供科学基础。

For a long time, the economists believed that the main role of agricultural machinery is to replace labor, and the role of increasing yield is limited. Agricultural experts study the yield increasing effect of machinery such as plowing, planting and fertilization machinery, but pay little attention to harvesting machinery. If the role of harvesting machinery is only to replace labor, it is difficult to explain the phenomenon that in the middle and late 1990s, when there was still a large number of surplus labor in China, the wheat combine harvest machine was rapidly popularized in the multiple cropping region in the Huang-Huai-Hai Plain. This study explains this phenomenon from the perspective of seasonal labor shortage from a new angle. The hypothesis is that the use of machinery would shorten the "empty time" (when there is no crop doing effective photosynthesis) of land and improve the available photosynthesis time for the crop of the next season, and therefore increasing yield. The above hypothesis is tested by empirical analysis of the differences of farmers' behavior of using harvesting machinery in different areas with different seasonal tension. The contribution of harvesting machine extension of previous crop to the next crop's production is also estimated. This job will improve the understanding of the mechanization development path for small-scale pure farmers.