Say your agri income is 1L and other income is 7L. Calculate tax on 8L say it is 72500 Then take agri income and lowest slab (2.5L/3L/5L as the case may be). Calculate tax on 1L plus 2.5L I.e 3.5L. it will be 5000. Now U have pay net tax of 72500-5000 I.e 67500 plus the cess