Agriculture Conservation Stamp Act This bill requires the U.S. Postal Service (USPS) to issue for a four-year period a semipostal to benefit certain Department of Agriculture (USDA) conservation programs. (A semipostal is a postage stamp that is issued and sold by the USPS at a premium, in order to help provide funding for a cause that the USPS considers to be in the national public interest and appropriate.) USDA is the sole agency to which the USPS may transfer funds received from the sale of the semipostal. USDA must use the transferred funds exclusively for programs authorized under title XII (Conservation) of the Food Security Act of 1985.