China??s main grain crops are rice, wheat, corn, soybeans and tuber crops. Paddy rice is the major grain crop in China, grown mainly in the Yangtze River valley and southern China, and on the Yunnan-Guizhou Plateau. Its output accounts for two-fifths of the total grain output. The output of wheat accounts for slightly more than one fifth of the total output of grain; it is planted throughout China but mainly on the North China Plain. The output of corn, grown in the provinces of northeastern, northern and southwestern China, accounts for one fourth of the total grain output. Soybeans are grown on the Northeast China Plain and the plains along the Yellow and Huaihe rivers. Sweet potatoes are grown widely in China, but mainly in the Pearl River valley, along the middle and lower reaches of the Yangtze River, the lower reaches of the Yellow River and in the Sichuan Basin.