Every such agreement made relating to county demonstration work in agriculture and home economics shall continue in force until the board of county commissioners, or the New Mexico college of agriculture and mechanic arts [New Mexico state university], shall terminate the agreement by notice to the other party or parties, such notice to be in writing delivered at least three months prior to the time fixed for termination of the agreement, and at the expiration of such period of three months, the cooperative relationship between said parties shall cease, unless otherwise agreed upon between the several parties.