Section 35. The county commissioners of any county may, subject to the approval of the commissioner of correction, purchase, take by eminent domain under chapter seventy-nine, or lease, in behalf of the county, a tract of land not exceeding five hundred acres in area for use as a county industrial farm, and may reclaim, cultivate and improve the same. The work of reclaiming, cultivating and improving the said land shall, so far as practicable, be done by prisoners transferred thereto as provided in section thirty-seven. At any time after said land has been reclaimed, cultivated and improved, the same may be sold if the county commissioners determine that it is for the best interest of the county.