Is Peninsular plateau fertile?

Yes, the Peninsular plateau is fertile and grows various crops, mostly cotton. One of the distinct features of the Peninsular plateau is the black soil area known as Deccan Trap. This is of volcanic origin, hence, the rocks are igneous. Actually, these rocks have denuded over time and are responsible for the formation of black soil. 

Further Reading:

• OUR COUNTRY – INDIA
• Geography Notes