Studies On Changes Of Cropping Structure And Their Influences In Shandong Since Ming And Qing Period

China is a large traditional agricultural country with a long history and emperors of each past dynasties all put the food problem in the first important place, which could be seen through the thought of "Country was based on agriculture" and "Food was most important for people". For owning the largest population in the world, governments of each dynasties all considered it the basic principle to solve the food problem. At present and during a long time in future, our government still put agriculture, especially planting in the most basic and important place, in which it is the huge duty for government to adjust the cropping structure in time according to national and international requirement.Prof. Perkins thought that it was a basic character of Chinese traditional agriculture that improvement of food production depended on the large input of labor and expense when without the technical improvement. Many experts in this field all agreed with Perkins that there was no technical improvement in Chinese traditional agricultural period and it was stagnated and dropped behind the western oil agricultural in Ming and Qing period. At that time, there was no large changes on the tools used for thousands of years and without chemicals and pesticides in production. But the population was doubled in 14 years from 12 billion in 1753 to 25.63 billion in 1767. What caused this most rapid improvement of population in Qing dynasty? So it's obviously wrong to think that agriculture became stagnation and laid behind in Ming and Qing period.Through studies on the agricultural development in Ming and Qing period, it found that great changes had taken place in our traditional cropping structure and cropping system and brought important influence on social economy through the introduction of American crops. Rapid spread of the American crops improved the cultivated areas and the grain yield in a large scale, which was the basic substantial guarantee for the sharply population...