(a) If any part of the principal consists of a right to receive royalties, overriding or limited royalties, working interests, production payments, net profit interests, or other interests in minerals or other natural resources in, on, or under land, the receipts from taking the natural resources from the land shall be allocated as follows:

1. (1) If received as rent on a lease or extension payments on a lease, the receipts are income.
2. (2) If received from a production payment, the receipts are income to the extent of any factor for interest or its equivalent provided in the governing instrument. There shall be allocated to principal the fraction of the balance of the receipts which the unrecovered cost of the production payment bears to the balance owed on the production payment, exclusive of any factor for interest or its equivalent. The receipts not allocated to principal are income.
3. (3) If received as a royalty, overriding or limited royalty, or as a bonus, or from a working interest or net profit, or from any other interest in minerals or other natural resources, receipts not provided for in the preceding paragraphs of this section shall be apportioned on a yearly basis in accordance with this paragraph whether or not any natural resource was being taken from the land at the time the trust was established. Twenty-seven and one-half percent of the gross receipts (but not to exceed fifty percent of the net receipts remaining after payment of all expenses, direct and indirect, computed without allowance for depletion) shall be added to principal as an allowance for depletion. The balance of the gross receipts, after payment therefrom of all expenses, direct and indirect, is income.