N.D. Cent. Code § 65-01-17

For purposes of the agricultural service exception to hazardous employment under section 65-01-02, an agricultural employer that engages in a custom agricultural operation, which is the planting, care, or harvesting of grain or field crops on a contract-for-hire basis, exclusive of hauling by special contractor, retains the exemption unless the employer's custom agricultural operations are based outside this state or require more than thirty actual working days of operation during the calendar year.