Abstract—A wireless sensor network (WSN) to automatically irrigate the crops using soil moisture content values obtained from the soil moisture sensor is designed. Gravity-feed drip irrigation is actuated according to the needs of the crop by using a relay to on a solenoid valve when the soil is dry, which is determined by soil moisture content below 60%. End devices communicate with the Coordinator via XBee communication links. Index Terms—Sensors, wireless, irrigation, solar power, ZigBee. I. INTRODUCTION Deployment of wireless sensors networks (WSN) in agriculture and food industry is still at the beginning stage [1]. Applications can be classified into five categories environmental monitoring, precision agriculture, machine and process control, building and facility automation and traceability systems. In this paper, wireless sensors were used to monitor the environment and to automate the irrigation system, all powered using solar panel. We are able to see that continual advancement in sensing and communication technologies has significantly brought down the cost of deployment and running of a feasible precision agriculture framework. Sensing and communication can now be done on a real-time basis leading to better response times. Monitoring system which connects the wireless sensors for detecting soil moisture, temperature, carbon dioxide and illumination can be done in the field-environment and connected to the internet [2], as well as inside a greenhouse using wireless sensor and SMS technology [3]. Wake-up synchronization phase were designed to periodically collect data from fixed locations minimizing the energy consumption [4]. For example, automatic data acquisition, transmission and processing for parameters such as temperature, humidity, illumination and voltage were carried out in a red bayberry greenhouse [5] and also in a smart crop monitoring system [6]. Virtual database systems were used to view spreadsheet database of the wireless sensor network [7] and tasks were performed using Manuscript received November 25, 2014; revised March 12, 2015. Angelina M. Y. Ho and Hawa Ze Jaafar are with the Department of Crop Science, Faculty of Agriculture, Universiti Putra Malaysia, UPM Serdang, 43400 Selangor, Malaysia (e-mail: angelinahomeiyi@gmail.com). Ionel Valeriu Grozescu and Muhammad Zaharul Asyraf Bin Zaharin are with the Department of Physics, Faculty of Science, Universiti Putra Malaysia, UPM Serdang, 43400 Selangor, Malaysia. programmable scripts [8]. The automation and efficiency on environment monitoring and control in agriculture are crucial. In order to control and monitor the environmental factors, sensors and actuators are essential. However, implementations are easier under protected structure than in outdoor applications. Therefore, in this paper we will be focusing on automated gravity-feed drip irrigation system in the field with the use of solar power to open the inlet valve. Water is fed to the crops without the use of pumps. This portable system will be useful in areas where there are no sources of electricity. II. RELATED WORKS Several applications using WSN in greenhouses has been developed, most of them make use of IEEE 802.15.4 or ZigBee. Some examples are greenhouse control and monitoring system [9], an automated agriculture system to monitor and control the environment in greenhouses with melon and cabbage [10] and integration a variety of sensors which can measure substrate water, temperature, electrical conductivity, daily photosynthetic radiation and leaf wetness in real-time. Benefits came from an improved plant growth, more efficient water and fertilizer applications, together with a reduction in disease problems related to over- watering [11]. There are also greenhouse auto control systems which collect information of internal environment and plants and stores it in database, and then control automatically in a remote place by using Web based on the greenhouse information [12]. A greenhouse auto control system contains temperature and humidity sensors [13] while in another system, leaf temperature sensor and leaf humidity sensor were added [14]. Both uses ZigBee based wireless sensor node. A ZigBee wireless sensor network was also designed using fuzzy control for drip irrigation which measured four parameters, soil moisture, temperature and light intensity and electrical conductivity for drip irrigation decision making [15]. III. METHODS A. Overview The diagram of the WSN system is shown in Fig. 1. It consists of a coordinator which collects data from the end devices over XBee communication links. The coordinator also acts as a decision maker to actuate the solenoid valve based on the parameters obtained. All of these devices are powered separately using 5W solar panels. Solar Powered Gravity-Feed Drip Irrigation System Using Wireless Sensor Network Angelina M. Y. Ho, Hawa Ze Jaafar, Ionel Valeriu Grozescu, and Muhammad Zaharul Asyraf Bin Zaharin International Journal of Environmental Science and Development, Vol. 6, No. 12, December 2015 970 DOI: 10.7763/IJESD.2015.V6.731