Conservation expenditure deduction permitted for payments to approved institutions, limited by approval term and prohibition on duplicate claims. Taxpayers may deduct payments to associations or institutions for carrying out programmes of conservation of natural resources if the programmes are approved by the prescribed authority and the recipient association or institution is for the time being approved; approvals are time limited to a maximum term and any expenditure allowed under this provision cannot be deducted again under any other provision of the Act for the same or any other assessment year.