When growing semiaquatic plants, such as rice and taro, paddy fields are used. These fields are filled with shallow water at least part of the year. Growing these plants is very labor-intensive. A lot of water is needed. Paddy-fields started next to the Yangtze River in China, in the Neolithic. Later, their use spread to other areas in Asia. Paddy fields are built next to marshes or using terraces, on a hillside.
Deepwater rice is not grown using paddy fields: It needs water over 50 centimetres (20 in) deep for at least a month.