"Basic purpose of adding agricultural income in total taxable income is to levy tax at a higher rate on non agricultural income. So logically going agricultural income is not included while calculating the ceiling u/s 87A, because agricultural income is not included in total income if your total income is less than minimum amount charged to income tax (I.e. 250000) for example ; if your other income is 240000 and agri income is 100000 than you will not be taxed at all. similarly if you have other income of 300000 and agri income is 100000 than only your both income be clubbed for the purpose of levy high slab rate. so the above rational can also be applied in 87A .