A lien or security interest is created by contract or by operation of law. No lien arises by operation of law until the time at which the act secured by the lien is to be performed. A security interest in personal property is governed by chapter 41-09, except that a bill of sale or security agreement, that is not a purchase money security interest, with respect to household goods, effects, furniture of married persons, or personal property exempt from execution is void unless the instrument by which it is transferred or encumbered is jointly executed by the husband and wife, if both are living. This section does not apply to transfers or liens arising by operation of law nor to security agreements relating to threshed grains made with any lending agency authorized to make commodity credit corporation loans on threshed grains.