The aim of the present paper is to propose an agricultural environment monitoring server system utilizing a low-cost Wireless Sensor Network (WSN). Several sensor nodes are scattered in fields several kilometres in size, and we propose collection of the information stored in the nodes by a mobile node, or mule. To cover long distances in a short period of time, we use an unmanned aerial vehicle (UAV), which retrieves the data stored in the ground nodes. In addition, the UAV may be used to acquire additional information and to perform actions. Its elevated position allows observation of the field with a perspective that is useful for detecting changes affecting crops, such as pests, diseases, significant changes in soil moisture, drought or floods. (C) 2015 Elsevier B.V. All rights reserved.