Study On The Introduction, Spread And Effection Of American Creal Crops

During Ming and Qing Dynasties, rapid population growth worsened the grain shortage. Under such social conditions, three high-yield varieties of American cereal crops: maize, sweet potato and potato, were introduced into China. They had played an important role to solve the problem of grain shortage. The thesis discusses their introduction, spread and utilizing in China and its emphasis is their influences on our country.The thesis clarifies some important problems and proposes some new viewpoints. Based on the related ancient local records and other agricultural history works, the thesis investigates the lines, times and means of introduction of the American grain crops into China and the first records of them in Chinese historical documents. Then the thesis researches the process of their spread in our country and concludes their diverse features of spread and distribution. Furthermore, the thesis gives a minute description of different means of utilizing these crops and reveals their importance on production and livelihood of common people.The most important contents are their influences on our country. They had pushed toward the development of agricultural production and social economy and played an important role in the dietary structure of person. To a certain extent, they had helped to accelerate the population growth at that time. At the same time, we cannot overlook their harmful effects on environment, which resulted from the development of barren hills by peasants cultivating maize.The original viewpoint of this thesis is the study of their influence on dietary structure. Having spread widely for hundreds of years, they became staple food grains of most people living in mountains areas. They also changed the livelihood of people living in traditional agricultural regions. Maize and sweet potato replaced the position of other low-yield grain crops. They became the most important food of poor peasants. This new change showed serious agricultural crisis in early twentieth century and to some extent, encouraged the trade of commodity grain.