The low cost of water has not led to a more efficient approach to water management. On the other hand, current legislation on water resources and the competition for water among agriculture, urban population and industries will affect the future development of ��green industry�� in this area, stimulating the search for more efficient solutions. Therefore, the design of a sustainable irrigation management system is one of the goals of RTD activities conducted by both public and private territorial entities (regional extension office, growers associations etc.)The paper is agriculture-oriented and then it considers only those sensors that can be implemented in irrigation controllers, such as traditional water-filled tensiometers and the more recent dielectric sensors. Expensive and sophisticated RZS�� currently used by soil and plant scientists, such as neutron probes [9], are not addressed. The paper also discusses how these sensors may be integrated into wireless networks for computer-controlled irrigation and employed for the application of innovative irrigation strategies, such as deficit or dual-water (alternate use of different water sources) irrigation.2.?Soil Hydraulic CharacteristicsApart from the direct measurement of water content by thermo-gravimetric methods, soil moisture conditions can be assessed by the determination of the matric potential (��m) of pore water or the volumetric water content (��), which is the volume of water in a certain volume of undisturbed soil. Recently, some sensors have been developed also to measure the soil salinity (namely, electrical conductivity o EC), as discussed later.The term ��m describes the amount of energy which must be exerted to extract water from a porous medium such as soil or soilless substrate. Therefore, ��m corresponds to the suction required for the water uptake by the plant roots. Moisture tension represents the degree of such suction and, according to the terminology used in crop irrigation management, it is a positive number; the higher the number, the higher is the tension and the drier is the soil. The relationship between ��m and �� (also called water retention curve) depends on the na
Over the past decade, there has been a surge of accidents in coal mines all over the world. Realization of environment monitoring and miner localization in underground mines plays an important role in mining safety. Wireless sensor networks (Wireless Sensor Networks: WSN) have attracted more and more research interest in coal mine applications for their advantages of self-organization, low cost and high reliability. Supported by the British Department of Trade and Industry, the Exeter College Camborne Mining Institution has constructed a high reliable wireless mesh network in mines [1]. Ohio State University has also carried out a WSN project for miner positioning and tracking in the U.S. [2]. Carnegie Mellon University has established a real-time coal mine WSN platform: FireFly [3]. Xia et al.