law: 20. Act to have an overriding effect.-
  The provisions of this Act shall have effect notwithstanding anything inconsistent therewith contained in any State law for the time being in force or in any instrument having effect by virtue of any such law other than this Act:
  Provided that a farming agreement or such contract entered into under any State law for the time being in force, or any rules made thereunder, before the date of coming into force of this Act, shall continue to be valid for the period of such agreement or contract.