Grain in ancient India

Hi, I'm an American student writing an essay about ancient India. However, I am having a hard time figuring out what type of grain was used in ancient India. I've read multiple sources that say rice was used the most and others that say wheat was used the most. I've also read about barley, millet, and oats but it is unclear to me which one was used the most. Anyways, which grain was used the most in ancient India?