Paddy Fields, Rice Terraces

• China
Although China's agricultural output is the largest in the world, only about 15% of its total land area can be cultivated. About 75% of the cultivated area is used for food crops. Rice is China's most important crop, raised on about 25% of the cultivated area. The majority of rice is grown south of the Huai River, in the Yangtze valley, the Zhu Jiang delta, and in Yunnan, Guizhou, and Sichuan provinces.
Rice appears to have been used by the Early Neolithic populations of Lijiacun and Yunchanyan in China. Evidence of possible rice cultivation from ca. 11,500 BP has been found, however it is still questioned whether the rice was indeed being cultivated, or instead being gathered as wild rice. Bruce Smith, an archaeologist at the Smithsonian Institution in Washington, D.C., who has written on the origins of agriculture, says that evidence has been mounting that the Yangtze was probably the site of the earliest rice cultivation. In 1998, Crawford & Shen reported that the earliest of 14 AMS or radiocarbon dates on rice from at least nine Early to Middle Neolithic sides is no older than 7000 BC, that rice from the Hemudu and Luojiajiao sites indicates that rice domestication likely began before 5000 BC, but that most sites in China from which rice remains have been recovered are younger than 5000 BC.
During the Spring and Autumn Period (722-481 BC), two revolutionary improvements in farming technology took place. One was the use of cast iron tools and beasts of burden to pull plows, and the other was the large-scale harnessing of rivers and development of water conservation projects. The engineer Sunshu Ao of the 6th century BC and Ximen Bao of the 5th century BC are two of the oldest hydraulic engineers from China, and their works were focused upon improving irrigation systems. These developments were widely spread during the ensuing Warring States Period (403-221 BC), culminating in the enormous Du Jiang Yan Irrigation System engineered by Li Bing by 256 BC for the State of Qin in ancient Sichuan. During the Eastern Jin (317-420) and the Northern and Southern Dynasties (420-589), land-use became more intensive and efficient, rice was grown twice a year and cattle began to be used for plowing and fertilization.