“Five grains” originally referred to five main crops, which were generally considered to be rice, proso millet, millet, wheat and beans. Millet was also called “ji” in Chinese, which meant “the god of the five grains” in ancient China. Combined with “she”, which meant “the god of the earth”, the term “she ji” referred to the state. 

五谷原指五种主要的粮食作物，一般认为包括稻、黍、稷、麦、菽，分别指水稻、黄米、小米、麦类、豆类。稷即粟，在中国古代被称为五谷之神，与土神合称“社稷”，成为国家的代称。

With the increase of crop varieties, the “five grains” gradually evolved into a general term for food crops. Major food crops in modern times were rice, wheat, sweet corn, sweet potato and soybean. 

随着作物品种增多，五谷逐渐演化成粮食作物的统称。现代比较重要的粮食作物是稻、麦、玉米、甘薯、大豆等。

Among them, corn and sweet potato were from the Americas and began to be planted in China during the mid-Ming Dynasty. By the early Qing Dynasty, they had spread throughout most of the country. 

其中，玉米和甘薯原产于美洲，明朝中期开始在我国种植，到了清朝前期，已经遍布我国大部分地区。

(Source:NationalMuseumOfChina)