This chapter explores the transformative agricultural advancements in JiangnanJiangnan during the Tang and Song dynasties, highlighting the shift from burn cultivation and water weedingCultivation and water weeding to continuous cropping and the rice–wheat double cropping systemRice-wheat double cropping system. These advancements not only increased agricultural productivity but also established Jiangnan as the national economic center of gravityEconomic center of gravity. The rice–wheat double cropping system’sRice-wheat double cropping system spread was driven by environmental factors and population density, with the Lake TaiLake Tai/Lake Tai Plain PlainLake Tai/Lake Tai Plain and Huainan region as key areas. Policy support from the Northern Song government and rising demand for wheat-based foods further encouraged its development. The influx of northern migrants during this period, especially following the An Lushan RebellionAn Lushan Rebellion and the Jingkang IncidentJingkang Incident, introduced advanced techniques like rice seedling transplantation and increased demand for wheat. The Southern Song era saw many northerners, including the emperor and royal families, relocate south, boosting wheat cultivationWheat cultivation and the rice–wheat double cropping systemRice-wheat double cropping system in Jiangnan. Ultimately, these elements combined to make Jiangnan the economic gravity center of the nation.