While the veteran is indebted to the board for land purchased, if he executes or there exists a lease or contract of sale of oil, gas, or other minerals, chemicals, or hard metals or a lease or contract of sale for timber, sand, gravel, or other materials that covers all or part of the land and that would result in the depletion of the corpus of the tract, at least one-half of all bonus money, delay rentals, and royalties received as consideration for or payment under the oil, gas, and mineral lease and at least one-half of all money received under a lease or contract of sale of any other minerals, chemicals, hard metals, timber, sand, gravel, and other materials or as much as is required, shall be paid to the board by the owner of the lease or contract of sale and applied by the board to the satisfaction of the indebtedness.