Gift of agricultural land to mother by son

Yes.  One family member may gift to son, daughter, father, mother, brother, and sister etc.  In most states, the stamp duty for gifts given to a family member is reduced. The stamp duty varies from one state to another state.  So consult in local S.R.O..  Gift tax will be levied.

Stamp duty is a State subject which differ from a State to another State.

You will have to pay full stamp duty for registration of "Gift Deed" as of a convenyance deed in Delhi.

Check it with a local lawyer/ Sub-Registrar / Document Writer in your State. 

Yes, son can gift his agricultural property to his mother.Stamp duty and registration charges differ from State to State .

It is generally 2% on value of gift+ user charges (Rs.10,000/) in some states.

Yes, many a State charge lesser or nominal stamp duty on gifts among persons in close realtion. The actual rate varies from State to State.