Wireless sensor networks (wsn) are widely used to monitor variables of interest in phenomena such as crop fields. In such a context the inclusion of a wsn strengthens the task of precision agriculture. For networks used in precision agriculture design challenges have emerged, like the need to achieve longevity for sensor nodes (serving as a data source), of not less than six months, corresponding to the cultivation periods. Previous works say that the routing technique used in wireless sensor networks is a high incidence factor in its longevity. In this paper, mor4wsn, a routing proposal coming from the adaptation of a multi-objective genetic algorithm (moga) approach is presented. mor4wsn creates tree structures from wsn deployment for proper routing to preserve the longevity in a wsn. Preliminary evaluation shows promising results.