Root systems play an important role in the absorption and storage of water and nutrients and in the synthesis of certain hormones. Root cutting may increase the growth and yield of rice because the soil disturbance resulting from root cutting has some beneficial effect on soil conditions, or excess root production may reduce shoot growth because it competes for carbohydrates. Moreover, differences among soils, varieties, and management systems exist. To determine whether a large root system is beneficial to yield, we conducted a field experiment on the effect of root cutting at the heading stage in Guangzhou, China, in 1998. The soil was a clay loam, fertilized with 150 kg N, 33 kg P, and 124.5 kg K ha-1. Five varieties were grown in the early-season and late-season experiments: Guang-Lu-Ai (short stalk) and Er-Qing-Ai (tall stalk) for the early season (March-July); Pei-Za 72 (hybrid rice), Feng-Ai Zhan 1, and Te-San-Ai for the late season (July-November).