Technological development in wireless sensor networks (WSNs) hasmade it possible to build up decision support systems for many real world problems. Agricultural applications are considered as one of the most interesting fields, which presents an increasing demand for decisionmaking and optimization systems.WAN-based solutions are used in agriculture to reduce cost and improve productivity by enabling real-time control of changes in the field, animals and crops states and machinery maintenance possibilities. This chapter highlights the importance of WSNs in agriculture and their use in controlling agricultural fields for farmers. As an example of a WAN application in agriculture, an automated irrigation system is presented. The system developed is based on the use of specific sensors and actuators to enable a real-time control of the irrigation task.