The oldest irrigation area in China has a farming history of more than 2, years. Which two places are referred to as "the south of the Yangtze River"?

Ningxia Plain and Hetao Plain.

The southern part of the Yangtze River on the frontier originally refers to Helan Mountain in Guliangzhou, but now it refers to Ningxia. The Yellow River enters from the southwest of Ningxia Hui Autonomous Region, and flows through Ningxia for more than 3 kilometers from south to north, giving birth to Wuzhong Plain and Yinchuan Plain. Yin and Wu provinces are known as "the southern part of the Yangtze River" because the Yellow River water is rich in rice.