Interest received from deposit by wife is argued as income

Dear contest, Income is nowhere defined in the family act, hence the interpretation of income can be derived from the Income Tax act. Under I.T. act 'interest from deposits' is held as an income. Income from deposits is classified as "Other Income" in the computation and also in the relevant ITR forms. Hence there is no debate on it being classified as an income.

Hence it can be argued to be the income of the wife and she will also be a co-extensive party to the maintenance of the child. You are also responsible for the maintenance of the Child and the court may take into account the proportionate income of both the parties before fixing maintenance.

If her interest income is nearing around 1/3rd of your income, you may not have to provide her maintenance, but the maintenance of the Child is co-extensive, so refer my above para for it.

Income from interest shall be treated as income of your wife which  shall be considered on the question of maintenance  to wife but you shall have to pay entire maintenance  for the child.  Besides, life style of you shall be considered at the time of determination of the quantum of maintenance of your wife and child.. 

I agree with Mr. Roy about the child's maintenance amount to be give by you.  The interest income by your wife if proved to be enough for her maintenance, the court may reject her claim for maintenance amount, but you have to prove the same beyond doubt to enable court to decide in your favor.