Where there is organized in the county a soil conservation association whose membership shall comprise bona fide landowners incorporated under the Cooperative Marketing Law, compiled in chapter 16 of this title, and when sufficient members of the association shall have agreed with the association by written contract to pay their proportionate share of the cost of purchasing equipment for analyzing soil for lime and phosphate content, the county legislative body is authorized, in its own discretion, to make an appropriation for the purchase of such equipment for use on farm lands of members of the association, and the county legislative body shall be reimbursed for the original cost of the equipment through the payment by each member of the association of that member's proportionate share of the cost of the equipment.