经济重心南移浪潮后的回流——以明清江南肥料技术向北方的流动为中心
경제중심남이랑조후적회류——이명청강남비료기술향북방적류동위중심
The Return after the Tide of Southward of Economic Centre --An Investigation Oriented on the Movement of Manure Techniques from South to North during Ming and Qing Dynasties