Taxability of agricultural income

Yes, any agricultural income to a farmer is tax-free, even if he has any income from other sources. Point is it should be justifiable.

in case of a HUF:

case 1: no income under any other source and agricultural income of 400000/-.

ans: entire agricultural income of 400000/-is tax free and hence tax amount is NIL.

case 2: income from other source of 240000/- and agricultural income of 400000/-

ans: since income from other source is below the basic exemption limit of 250000/-, hence no taxation on income from other source of 240000/- and agricultural income is tax free. hence tax amount is NIL.

case 3: income from other source of 500000/- and agricultural income of 400000/-

ans: partial taxation will apply since income from other source is more than the basic exemption limit of 250000/- and tax will be calculated as follows:

income from other source + agricultural income = 900000/-

tax on 900000/- = 105000/-

basic exemption limit + agricultural income = 650000/-

tax on 650000/- = 55000/-

total tax implication = 105000 - 55000 = 50000/-

please suggest if my interpretation is correct?

Yes correct, just cesses to be added in case 3.