For the purpose of encouraging agriculture and the holding of agricultural exhibitions of farm products, an incorporated agricultural association, or county, conforming to the requirements of this act, is entitled to receive from the Commonwealth an annual sum, not exceeding one thousand dollars, equal to the amount paid by such association as premiums for exhibits of farm products at its annual exhibition, exclusive of premiums paid on trials of speed. Such premiums shall be paid only upon those farm products of this Commonwealth that are determined to be eligible for premiums by the Secretary of Agriculture, whose determination shall be made from the premium list prepared by the State Farm Products Show Commission, and such other premium lists as the Secretary of Agriculture shall determine.