Final Report Summary - SMART-PADDY (Smart on-line water salinity measurement network to manage and protect rice fields)
Executive Summary:
The SMART-PADDY project developed an on-line wireless sensor network capable of measuring electrical conductivity (EC), and thus salinity, in rice paddies, drainage or irrigation channels. This system is capable of substituting the expensive handheld meters used currently in the field and can be used to measure the salt content of the water used for watering the crops in a remote and accurate way. Indeed, the SMART-PADDY system can measure electrical conductivity by measuring electrical impedance in a range between 0.3 to 6.0 dS/m with an uncertainty of ±0.5 ºC. One of the most important features of the system is its ability to provide remote readings of the salinity in rice fields in a timely manner. Rice-growers have been able to read their salinity online using a tailored user interface which graphically represents the online readings in the field that are transmitted wirelessly from the field to the database. The functioning of the SMART-PADDY system has been proven to withstand the harsh environment of rice paddies and offer an extra functionality based on a novel development: it is capable of detecting biofouling or electrode corrosion which may alter the EC readings. In this way, the user can detect a misreading caused by an alteration on the electrodes and amend this problem in the field in spite of obtaining false EC readings.
The SMART-PADDY system is composed by autonomous nodes containing one (or up to 3) EC sensor(s), a communications module and an energy harvesting unit made of solar panels; a gateway receiving the readings of all nodes in the area and storing the information on a local database while uploading it to the cloud; a user interface displaying the information coming from the field.
SMART-PADDY was tested in 4 different rice cultivation areas in Europe and proved to provide valuable information to all of them. It was installed in rice paddies measuring water salinity at nearly root level, in an irrigation channel and in a drainage channel. This allowed to enhance the management of the water flooding in the paddies but also to improve the management of pumping stations in channels and to detect sea water intrusion. It was demonstrated that the SMART-PADDY system is able to provide the same accurate information than a high quality handheld meter while allowing a real time, remote and user friendly monitoring of this information. This functionality was proven to work for managing salinity in rice crops and therefore increasing the yield and optimizing the physiological characteristics of rice.
The SMART-PADDY system that led to the beginning of a patent process delivered tailored information to the rice-growers but could be used in many other industrial applications as electrical conductivity is a parameter commonly used in many sectors.
Project Context and Objectives:
Rice is the main crop in wet areas such as river deltas and is an essential tool in Europe in managing protected ecosystems. Irrigation water is a key factor in the production of rice and water quality has a major impact on crop yield as a result of tolerance of rice to factors such as dissolved salts. Rice is more water consuming than many other crops; in continuous flooding cultivation it takes about six times the water required by wheat. Due to increased water use in coastal areas, the sea intrudes the water table and rivers, and seawater floods nearby fields during storms in the Mediterranean area. The result is increased water salinity, which reduces yield in rice crops and increases soil salinity. Nowadays, water condition is for the most part assessed by visual inspection of the crops and, when excess water salinity is suspected, fields are irrigated by flooding them. In areas where water salinity is endemic, rice paddies are continuously irrigated with river water to reduce water salinity. This is a remedial solution that requires enormous volumes of water and considerable energy to pump water.
Water salinity can be accurately determined by measuring its electrical conductivity (EC). Measuring EC at the water inlet and outlet of each paddy field can help in monitoring the “washing” effect of irrigation. Moreover, measuring EC at points far from water inlets and outlets can help in assessing water salinity in a given paddy field and at different depths in drainage channels can help in managing water salinity in larger areas.
Based on this background the SMART-PADDY project developed a wireless sensor network comprised of low-cost EC measurement nodes and an autonomous power supply based on energy harvesting, that is capable of transmitting readings of water salinity in paddy fields in real-time to a central server. This data, accessible via internet, enables cultivators to effectively manage and protect their paddy fields and greatly reduce flood water consumption. Initial tests were made in the laboratory and the system has been validated in four different field set-ups, which proved the correct functioning of the system at various key locations in rice paddies.
The overall objective of this project will centre on the development of smart on-line water salinity measurement network to manage and protect rice fields that will be based on a wireless sensor network (SMART-PADDY) comprised of low-cost EC measurement nodes and an autonomous power supply based on energy harvesting, that will be capable of transmitting readings in real-time to a central server.
Firstly, the needs and specifications of the rice-growing industry were defined to drive the requirements of the different parts of the system. These included probes with 10-15 cm in diameter, 1m water resistant, IP67 or IP68, transceiver working at 433 MHz ISM band with up to 10 dBm power and at least, -110dBm sensitivity, less than 25 mA in receive and transmit mode, 10 MHz processor speed microcontroller with 32 KB memory and sensors ranging from 0.5 to 5 dS/m with 0.25 dS/m uncertainty and 0.01 dS/m resolution withstanding temperatures from -10 ºC to +60 ºC. The system should be solar powered and with external communication capability. The user interface should show graphs on the mean readings in the field, graphs for one specific node and possibility to select periods of time to be graphically represented.
Laboratory research conducted during the project showed that pulse wave excitation (PWE) and electrical impedance spectroscopy (EIS) are successful methods to determine EC in water. The developed sensors offered EC measurements based on these two methods to achieve a measuring range of 0.3 to 6 dS/m in an automatic temperature compensation (ATC) range of 5 to 35 ºC. The sensors were composed of a flat two-electrode EC cell based on two AISI 316 stainless steel acorn nuts with a PVC plastic body and volume delimiter to ensure a repeatable cell constant. The built sensor was based on the user needs and represented a low-cost, novel –and patentable – EC sensor.
An on-line wireless system for the measurement of salinity was designed and developed based on the requirements defined initially. This wireless sensor network (WSN) comprised independent nodes with Radio Frequency (RF) technology that communicated with a gateway device which gathered all data coming from the sensors and stored it locally and in a web server. The WSN was optimised in terms of distance of communications and power consumption to meet the overall requirements of the system.
The newly developed sensor and WSN systems were integrated into a single unit which comprised the SMART-PADDY system. Two new PCBs were designed (one for the RF and the other for the multiplexing and power management) following the research and tests performed previously. The best solution in terms of design simplicity were chosen in order to obtain an easy to assemble and disassemble device. A PVC encapsulation was designed which offered the required water proofing capabilities. The system was built to allow laboratory testing with a final set-up. An accessible web interface was also developed to show the data obtained in the field in a graphical and understandable way as the front-end of the SMART-PADDY system.
Laboratory and parallel field testing was carried out in order to validate the proposed SMART-PADDY system. The nodes were able to withstand the harsh environment found in rice paddies while the sensors offered excellently accurate EC measurements while the WSN managed to retrieve all data and store it locally and in the internet. The user-interface was perfected following the recommendations from the end-user SMEs to represent data in the most user-friendly possible way. A validation plan was put in place to evaluate the effects of the SMART-PADDY system in irrigation management and therefore on the physiology and quality of rice. Recommendations for future improvements to obtain a fully commercial version of the system were outlined.
The SMART-PADDY system proved to be an accurate and reliable tool for the management of rice paddies and improving the quality of rice. The close monitoring of salinity during the cultivation stage allows for a better regulation of irrigation and thus improves the quality and yield of rice.
The process of validation of the SMART-PADDY system took place in the 4 locations of the end-users SME partners in the project and involved the testing of the system in rice paddies (Greece), irrigation channels (France and Seville) and in drainage channels (Ebro Delta). This testing at different sites of a rice area allowed to evaluate the versatility of the system and to demonstrate the SMART-PADDY performance and features both within the consortium and beyond to a large number of industry stakeholders from the rice-growing sector.
While developing the SMART-PADDY technology, concern was also given to the cost of selected materials and components to guarantee the future exploitation of the SMART-PADDY system by keeping it of sufficiently low cost to ensure its uptake by the rice growing sector. The developed system cost is around the 2000€ per complete unit (including a sensor, gateway and software) which is in the range accepted by rice growers for such a device.
The overriding goal of this project was to ensure that the resulting pre-competitive SMART-PADDY prototype fulfils the set requirements to ensure its further development post-project into a fully industrial system that is taken to market, where its beneficial environmental and socio-economic impact will be felt at European level.
Project Results:
The main technological result of the SMART PADDY project has been the demonstration of the feasibility of an affordable, real time system able to monitor the electrical conductivity (EC) of water in rice paddies as surrogate for water salinity and its effectiveness in protecting rice plants. This is a leap forward in water management and precision agriculture as no wireless EC sensors were available in the market and the existing sensors are too expensive for multiple units to be installed over a large area. This result has implied several technological achievements and has established a clear advance in measurement science. In order to describe the specific results, the ten initial scientific and technological objectives of the project, are summarized below:
1. To research the needs and specifications of rice cultivators and use findings to define the specifications for the SMART-PADDY system.
2. To carry out research into the electrical conductivity sensors that will be effective in continuously measuring the salinity in paddy fields.
3. To develop the telecommunication system to ensure the effective transmission of data from the SMART-PADDY sensors in-field to a remote data repository.
4. To research the energy consumption of the system in order to ensure up to two years autonomous operation.
5. To integrate and test the system at laboratory level.
6. To design a flexible, easy to use, data-driven web-interface and back end software in order to process the retrieve data, as well as control instructions from operators (WP4).
7. To install the system in the field and to carry out trials with the SMART-PADDY system in a real field environment and to validate the performance of the system.
8. To study the salt effect on the physiology and quality of rice by carrying out rice agro-physiological trials and analysis, such as yield, salt injury, photosynthesis, K/Na ratio and quality.
9. To carefully outline recommendations for future development work for full commercial system.
10. To facilitate the uptake of the SMART-PADDY results by the participating SMEs, as well as a wider audience of rice growers, a comprehensive series of demonstration activities will be carried out that will showcase the performance of the prototype for measuring water salinity in PADDY-FIELDS, and communicate its benefits for water consumption, yields, economic returns and environmental protections.
The research of the first objective confirmed that current technology cannot provide the real time information offered by a system such as SMART-PADDY. It also confirmed the clear disposition of the industry to invest into new and innovative technology for improving the quality of their products and optimizing the water use. The industry consultations also provided valuable information regarding the frequency of measurements, the periods during the rice growth process where salinity measurements are more important and the measurement accuracy required for limiting yield losses. This information was taken into account for the definition of the SMART-PADDY specifications.
The research of the first objective also led to the identification of at least three different scenarios: salty irrigation water and normal soils, salty soils and quality irrigation water, and salty soils and water. EC sensor placement depends on the case. When only water is salty, it can be measured at water pumping stations or main irrigation channels. When only soil salinity is high, paddy water conductivity must be measured. Further, EC measurement at different depths in drainage channels can provide information about large areas and help in deciding when to increase the drainage flow by increasing the volume rate of pumps that empty channel water. The acceptable sensor node cost is much lower in paddies than in the two other cases and the EC sensor of SMART PADDY has been designed according to this most restrictive case.
The second objective of the project was the research and development of an EC sensor able to continuously monitoring water salinity in inundated paddy fields while fulfilling the low acquisition and maintenance costs required by stakeholders. EC sensors comprise an EC cell and the interface electronics to obtain the desired data. Usually, low cost EC sensors use two electrodes instead of four and must operate at a frequency high enough for the electrode impedance to be negligible as compared to water impedance. For high water conductivity, this implies measuring at a high frequency but then cable capacitance becomes important and contributes to the result. In order to avoid this effect, electronic circuitry can be placed next to the electrodes so that no cables are required between them, but even by so doing there is no guarantee that electrode impedance will not affect the result. This is because electrode material must withstand a saline environment, hence must be corrosion-free, and these materials do not necessarily establish a low impedance interface when immersed in saline water. Further, soiling and biofouling affect electrode impedance, which makes it still more uncertain which frequency to measure at in order for the effect to be negligible.
In order to solve this problem a novel approach to two electrode impedance measurements has been conceived: instead of trying to avoid electrode impedance, the overall impedance between the two electrodes is measured and then a procedure is devised to identify the respective contribution of electrodes and water to that impedance. This identification requires a method to distinguish both impedances.
It turns out that electrode impedance can be modelled by a resistance in parallel with a capacitance, which values depend on the frequency on the current through them, whereas below, say, 1 MHz, water can be modelled by a resistance. Overall, the measurement cell can be modelled by a simplified Randles circuit, which includes only three components, normally identified by measuring at three different frequencies, or at two different frequencies if the real and imaginary parts of the impedance are simultaneously measured. Those two or three frequencies must be apart enough for the respective measured values to be different without requiring very high resolution, which is very difficult to obtain in a low cost sensor. But in any case, solving the resulting equation system asks for computation resources unavailable in a low-power, low-cost system.
Prior art to overcome the need for measurements with sine waves from different frequencies is to inject voltage or current pulse waves into the measurement cell and then measure the resulting current or voltage at three different points and solve the equation system based on the ideal pulse response of the simplified Randles circuit. But, on the one hand, this does not overcome the need for solving an equation system, now with exponential functions, and on the other hand, actual pulse response includes transients attributable to parasitic impedances, particularly just after the leading edge of the pulse has been applied, and it turns out that the initial response value after the pulse has been applied has the information about water resistance.
During laboratory experiments to evaluate alternative circuits for impedance measurements based on pulse waves, a novel method has been developed to reduce those transients by reducing the slew rate of the leading edge of pulses. This method, however, cannot be directly applied when pulses are generated with low-cost microcontrollers.
A detailed analysis of the equivalent measurement circuit, later confirmed by laboratory experiments, revealed that the imaginary part of the EC cell impedance was due only to the electrodes. This lead to the following method: measure with a 100 Hz sine wave in order to inform about electrode impedance, hence electrode condition, and measure with a voltage pulse wave to determine water conductivity regardless of electrode condition. To avoid errors because of transients that can affect the initial value of the pulse response, two samples are taken at particular times after pulse injection and the initial value is calculated by an original interpolation method based on analytical properties of exponential functions, which performs better than linear interpolations described in some patents. The joint use of a low-frequency sine wave and a voltage pulse to measure liquid conductivity and at the same time assessing electrode condition is novel and patentable. Liquid conductivity is measured in many industrial and environmental applications other than water management in paddy fields. Overall, this approach to two electrode impedance measurements is a definite contribution to measurement science.
To achieve the low cost required for electronic circuitry to measure the impedance of the conductivity cell, and water temperature (required to compensate for the temperature coefficient of water conductivity, a low-cost microcontroller unit (MCU) that integrates 12 bit ADC and two DACs, and an analogue input multiplexer was selected. A previous uncertainty analysis demonstrated that 12 bit resolution (and ADC uncertainty for common MCUs) was enough to meet system specifications. This implementation of pulse-based impedance measurements by using a common MCU is a relevant technological result.
To reduce the analogue hardware between the EC cell and the MCU, there is no analogue demodulator to measure the real and the imaginary parts of the impedance. Instead, quadrature synchronous sampling is used, which implementation by a low-cost microcontroller is another relevant technological result because it leads to the design of compact, low-power, low-cost Electrical Impedance Spectroscopy (EIS) systems. In fact, SMART PADDY nodes measure impedance also at 83.3 kHz for redundancy. Further, the water temperature sensor is directly connected to the MCU without any intervening active component, which also reduces cost, power consumption and components number, hence improves reliability.
The design of the EC cell is also original. Low cost forbids the use of expensive materials or assembling techniques. Here it was decided to use a single EC cell design for the three different EC probes required to measure water conductivity at each of the three different scenarios identified. After several laboratory tests with saline water, it was decided to use Grade 4 (AISI 316) stainless steel acorn nuts (and bolts, common marine hardware) as electrodes and PVC for the body of the EC cell. A PVC volume delimiter determines the path of electric currents hence making readings independent from the closeness of the sensor to walls or to paddy bottom, and also from water movement. Overall, this design provided a highly repeatable cell constant for the 5 units built for the preliminary field tests of the first year and the 10 units built for the field tests of the second year.
The automatic temperature compensation (ATC), which is a required feature for all autonomous EC meters, has been designed to rely on a temperature sensor that is not in direct contact with water. Instead, the temperature sensor is placed on the internal side of the bottom of the EC cell. This temperature measurement, together with the measured impedance, permits to identify water absence and inform about that condition.
Finally, meeting discussions showed that it was convenient that sensor nodes retained the data logging capability designed in the EC sensor for the preliminary field tests and external communication features that allowed the EC sensor to be diagnosed even if it was not connected to any transceiver. This can be of help during manufacturing and troubleshooting.
The third objective concerned the telecommunication system to link the SMART-PADDY sensors to a remote data repository. Initially, a MESH (Multipoint Enhanced Signal Handling) of nodes was expected to be used, but none of the three scenarios required it. The adopted solution in the end comprised Radio Frequency (RF) communication between the sensors and the Gateway in the unlicensed 433 MHz ISM band but no need of communication between nodes was required although the protocol was studied and developed in case it was needed. The selection of this transmission frequency was made according to the price and capabilities criteria. In the market there are several ISM transceivers available which are cheap and at the same they offer important features like high sensibility, low power consumption and programmable transmission power. This satisfied two important requirements of the SMART-PADDY system: it offered low-cost Electrical Conductivity sensor nodes and an autonomous functioning over a long period of time. Moreover the use of the ISM 433 MHz frequency allowed the implementation of a small-sized antenna that can be easily embedded in the sensor node mechanics. The gateway was the central device gathering all the data coming from the sensors and storing it locally while uploading all information to the cloud server. It was formed by an Alix 3d3 embedded PC system board with an RF transceiver and a USB modem. It used UMTS/GPRS or Wi-Fi protocol to communicate externally with the cloud server.
As for the power supply system, which was the fourth objective, sensor nodes are supplied from solar cells as initially planned. They take less than 30 % of the top surface of the probes, which external diameter is less than 9 cm. This way, those cells are inconspicuous and do not attract vandals. In the first sensor prototype, the low supply voltage selected (3 V) was not enough to obtain the desired performance of the MCU so that it was raised to 3.3 V. Energy harvesting and power conditioning worked as required, the main problem being their installation in drainage channels because it may be convenient to rely on existing civil engineering works (bridges or concrete walls) but this may imply that solar cells remain several hours in the shadow. In these cases it could be advisable to split the probe in two bodies instead of using a single rigid body. Then the part with the transceiver could be fixed on a surface with a convenient orientation for solar energy harvesting whereas the part with the sensors must necessarily be immersed into the channel. Nevertheless, it must be considered that in all field tests a reading per hour was taken and communicated, that in some cases, particularly in drainage channels, was too high, as demonstrated by the large amount of repetitive readings obtained. If measurements were transmitted only three or four times a day, no special precaution for solar cells orientation could be necessary.
System autonomy in the proposal was expected to be two years. End users, however, informed that field probes would normally be retired before harvesting, which offered an opportunity to replace batteries if required. In practice, energy harvesting relies on secondary (rechargeable) batteries that can last for many charge-recharge cycles. Therefore, besides the convenience of retrieving probes to avoid any damage from or to rice harvesting machinery, no actions are required other than replacing degraded electrodes or EC cell calibration. Nevertheless, field tests have shown no effects from electrode soiling and fouling on EC measurements neither did EC cells need any calibration after cleaning them with tap water.
The fifth objective was to integrate the system and test it in the laboratory. Sensor probes that include a single EC cell comprise to printed circuit boards (PCB): one with the EC sensor electronics, next to the electrodes in the EC cell and another one close to the top of the probe that includes the control unit, the transceiver, and the energy harvesting and power conditioning circuits. Probes with the EC sensors include a PCB for each sensor and a single control and communication unit (CCU). Power and signal communication between EC sensor(s) and the CCU is performed through a custom-designed hub that is embedded into the CCU PCB. This substantially reduces the number of cables between both units and it is a solution that can be applied to other autonomous sensor nodes.
In order to reduce software complexity in sensor nodes and to avoid the need for any changes derived from possible communication system updates, all calculations required to obtain water conductivity from the measured resistance and for temperature compensation are performed in the server rather than in local processors or the gateway. Similarly, sensor calibration is performed via web so that there is no need to disassemble and reassemble probes.
The body of the three EC probe types is based on common (non-pressure) PVC piping hardware to reduce assembly costs. Both the EC cell, during the preliminary field tests of the first year, and the three different probes during the field tests of the second year have performed correctly. There were no water intrusion problems or cable disconnections in spite of their transport and installation. The system comprised a modular design in which the electronics could be assembled and disassembled without major difficulties and with no connectivity issues. The conductivity sensor was embedded in the lower cap of the mechanical design and had a constant volume cell around it which was secured with nylon bolts. The antenna and the PV cell were located in the top part of the probes. The antenna was held inside by a nylon screw while the solar cell was on top of the top cap where received the necessary sunlight. To ensure the waterproofing of the system, three piece systems with rubber joints were used in those parts where the water was in contact with the probe.
The sixth objective was the web interface, which was implemented using open-source web technology. The user interface system was based on MVC (Model-View-Controller) concept that isolates database with its processing (the Model) from the data manipulation (the Controller) and presentation of the data in web based user interface (the View). The model layer (where the database belonged to) defined the business logic of the system. The Controller system software architecture was a piece of code that called the Model to get some data that it passed to the View for rendering to the client. All requests were managed by front controllers. These front controllers delegated the real work to actions that were logically grouped into modules. The View was what the user interacted with. This layer was mainly made of PHP templates, which allowed a rapid development of views which were compatible with any viewing device (PC, phone or tablet) and any web browser. The view part of the Smart-Paddy software was developed in "open-source" technologies. The languages and structures which were selected were a MySQL database with PHP and AJAX (Asynchronous JavaScript and XML). As a data-interchange format inside the system JSON (JavaScript Object Notation) was used. It is a lightweight format, is easy for humans to read and write and for computers to parse and generate.
The designed web-user interface was refined and tailored to the end-users recommendations and needs to offer a user-friendly and useful system to understand and analyse the data coming from the field sensors.
The seventh objective was field installation and trials. The four installations were smoothly performed. Anchorages were adequate, did not require any special tools or skills, and withstood water and wind force and rain. Probes could be retrieved at the end of the season without any damage. Trials could be performed for more than four months in paddy fields, enough to monitor them during a complete rice-growing season, and for more than two months in water channels and pumping stations, which was also long-enough to assess system performance. A minor handicap was that 2013`s season was especially good in the four places and only a few high-salinity events were detected. No-water conditions were easily detected from the data obtained.
EC and water temperature readings from the SMART PADDY system were compared to those of commercial handheld EC meters and the correlation was very good, even for EC values below the specified range (0.5 to 5 dS/m). Conventional cultural practices, such as use of agrochemicals, have not interfered with system operation in the EC or temperature measurements. Sensor nodes close to high-power equipment such as water pumps were not affected by electromagnetic interference.
Electrodes during field experiments could not be continuously monitored by visual inspection. In order to ensure that EC measurements performed after long-time immersion were good, changes in electrode impedance during continuous water immersion were monitored for 70 days in a separate laboratory experiment. Changes in electrode impedance did not affect the water conductivity value measured. This validates the proposed measurement solution. Electrodes in the retrieved probes were not so affected by biofouling as those in the water tank in the laboratory, exception made of that in the drainage channel.
The eighth objective concerned the trials and analysis of the effects of salt on the physiology and quality of rice. Analysis of the four different treatments applied in the experimental rice paddies in Greece confirmed that salinity levels that result in EC > 3 dS/m during the 20 first days after sowing reduced yield and many agronomic and quality characteristics of rice. This is important because it implies that areas with high soil salinity need prolonged irrigation to wash away excess salt. That salt may be a result of sea intrusion and lack of irrigation during winter, but also from practices to combat some pests that consist of irrigating fields with salty water in winter. The SMART PADDY system can help in determining when salt has been sufficiently washed away before sowing, in addition to monitor paddy water salinity during all growing season.
Analysis of the harvested rice showed that the following traits were affected by salt toxicity: height, chlorophyl concentration index, tillering, dry matter accumulation, spikelet length, dehusked length, width and their ratio, 1000 grains weight, whole milling yield (breakage of the grains during the milling process), Na and Na/K ratio.
The ninth objective aimed at outlining recommendations for future development work leading to a commercial system. Laboratory tests, preliminary field tests, field trials in four different places to fulfill the requirements of four different scenarios, technical and general steering committee meetings and demonstration sessions where interaction with possible users was direct provided plenty of information about improvements to be considered in a design review, technical features that could be easily added and possible applications not initially considered.
These future improvements apply either to all uses or only to particular uses, the main difference being whether sensor nodes are to be installed in paddies or on channels, and in this second case, on whether they carry a single water conductivity sensor or several (up to three) sensors. In general, design provisions included to enable field testing by an expert technician would not need to be included in a commercial product because, on the one hand, information about internal status can be made available to technicians via web and, on the other hand, it would be easier to replace malfunctioning probes than to repair them in situ. However, data logging capability in the gateway is instrumental to retrieve information when the internet connection fails, which is not an unusual event. Similarly, when several nodes are used in a relative large area, which increases de risk of failed connection to the gateway, keeping the data logger feature in each node, as designed for the preliminary field tests, could be convenient and will not require any hardware modification.
All applications would benefit from an alarm about possible wrong water temperature measurements, which implementation would be easier if the sensor that measures air temperature inside the (bottom of the) probe is kept in future designs.
In probes with a single sensor, those for paddies or water pumping stations, the transceiver unit could be directly connected to the EC sensor unit in the probe, i.e. the no hub for power and data communication is required. To cover sensor-gateway distances that exceed the available RF range, a new type of “relay node” could be designed that includes only the power supply and the transceiver if that node is to be placed outside a paddy field.
With regard to the mechanical design of the probes, it would be convenient to have a means to ensure that electrodes in the EC cell are really perpendicular to the windows of the cell, instead of relying on the criterion of the person that assembles the probe.
The gateway could be programmed to accept signals from other sensor nodes that measure different quantities, related to rice cultivation or not.
In order to implement Electrical Impedance Spectroscopy based on sine waves by using the technology used in SMART PADYY, it would be convenient to modify the timing of measurements performed with high-frequency sine waves in order for some transients to extinguish down before signals are sampled. The specific changes required are described in Section 2.1 of Deliverable 5.3.
Objective 10 targeted the uptake of the SMART-PADDY results by the participating SMEs and the larger rice-growing community in the participating countries. To this end, 3 demonstration activities were planned and carried out in Greece, France and Spain. The first one, held in Chalastra, Greece on the 25th April 2013, gathered 33 attendees comprising rice growers, millers and agriculturists. The demonstration showed the functioning of the system and its installation. The session was filmed and the feedback questionnaires gathered from the attendees reflected a high satisfaction among the participants. The second demonstration activity, held in Chamone pumping station, Arles, France on the 28th June 2013 gathered the 8 participants among which there were the farmers using that pumping station and two agronomy students. The demonstration showed the working system in the field, and many issues were discussed during the session. The third demonstration activity was held in Ebro Delta, Spain, on the 18th September 2013 and gathered 6 rice growers and the participants of the European Project RICE-GUARD (606583). The session showed the installed system working in a drainage channel measuring salinity at 3 different heights and data shown in the user interface in real time.
The demonstrations served to show the rice growing community of the participating countries together with relevant stakeholders the correct functioning of the SMART-PADDY system to promote the interest of farmers across Europe. This objective was fulfilled completely by completing 3 demonstration activities and obtaining valuable and positive feedback from the rice-growers.
The SMART-PADDY system serves the purpose it has been developed for. It is a low-cost system able to continuously monitor water salinity by measuring electrical conductivity of water in rice paddies, irrigation channels, pumping stations and drainage channels. Therefore, it provides an excellent tool for irrigation water management either for individual farmers or for farmer cooperatives or other associations. It can also be used as a research tool to study the effect of paddy water salinity on rice yield and quality. In this regard, it is worth to consider that in some cultivation areas outside Europe, irrigation water available does not normally have good quality, which is different from the scenarios here considered where irrigation water had excessive salinity only at particular times of the day or season.
Potential Impact:
There are numerous socio-economic impacts that will be derived from the results of this SMART-PADDY research project.
Central to the expected socio-economic impacts is the boosting of the competitiveness of rice farmers and companies along the rice value chain- by improving the crop yield and quality. Since the reduction of the intervention price for rice by 50% in 2004, the rice sector has had to readjust to become more competitive in front of the Asian market imports. Overall, the European rice sector faces a delicate situation and needs to benefit from any technology or system capable of enhancing their yield and therefore overall income.
Despite prices of rice falling back from the average prices in 2008 and 2009 they remained well above historical price levels, with the price in 2010/11 being between 61% and 71% above the values of 2006/07. In 2011 the global trade of rice reached record levels and prices were around 22-23% higher than those of 2010. These figures suggest a considerable price volatility on global rice markets and reflect a strong dependence on climatic and weather related factors. This means that any system capable of controlling the natural variables of rice production –such as salinity, will be a very valued technology by the rice-growing sector. This need is enhanced by the fact that the trends in the EU show that the consumption is growing faster than the domestic production, therefore imports are larger and include varieties of rice not grown in the EU. Thus, EU rice growers are in need to increase productivity and yield and the rest of the rice-growing continents need to ensure a stable and productive activity in order to meet with the needs of the market. SMART-PADDY can help fulfil these needs across the global rice-growing community.
Taking into account the economic aspects and the benefits for the rice growing industry by achieving for example a reduced irrigation water consumption or an increased time management, SMART-PADDY technology is expected to have a significant impact on the rice growing industry, which is demanding of such improvements to reduce irrigation water usage, production costs and enhance crop yield, and will therefore have a direct positive effect of the environment.
Moreover, the impact of SMART-PADDY will not only affect EU rice-growers, but it can have a global effect on the worldwide rice growing community. Production is geographically concentrated in Western and Eastern Asia with more than 90 % of world output. China and India, which account for more than one-third of global supply over half of the world's rice. Brazil is the most important non-Asian producer, followed by the United States. If the SMART-PADDY system owners (OSV and BEGAS) manage to commercially exploit the system with a global patent, the sales could boost to all the producers across the rice-growing countries. This would imply a large benefit for the participating SMEs while ensuring an improved management of salinity in rice paddies worldwide.
The economic impact associated to SMART-PADDY will expand to several sectors across the value chain apart from the rice-producing end-users:
i) Producers of raw materials, components and equipment:
The electronics producers will benefit from the demand of components for the SMART-PADDY system which will require the elements for the EC sensor system, the hub and energy management system and the RF transceiver system together with the solar cells for energy harvesting. Moreover, the PVC producers and suppliers will also have to provide the necessary elements for the mechanical housing of the probes.
ii) Manufacturing and distribution companies:
The manufacturing companies will have to produce and program the SMART-PADDY hardware and software and deliver an off the shelf package for the final retail or industrial agricultural companies to distribute the system to the end users. This will increase their activity and number of orders and in return increase their profit substantially.
iii) Agricultural machinery suppliers
The responsible companies for delivering the SMART-PADDY system to the final users will be those dealing directly with rice-growers, mainly supplying the agricultural tools needed for their operation. They could also be supplying the novel SMART-PADDY system as an innovative tool for the rice-growing communities and therefore increasing their share of sales and support and in return, their benefits.
The increased productivity and growth generated by the more accurate control of salinity in irrigation water will directly affect the job creation and rural employment, offering a social benefit to the SMART-PADDY system. In areas where rice is cultivated it is often the only source of income of the communities inhabiting those zones and therefore tools such as SMART-PADDY will be welcome by all agricultural land owners and associations. Moreover, taking into account that rice provides 21 % of global human per capita energy and 15 % of per capita protein; that rice is the second largest produced cereal in the world while world rice consumption increased 40 % in the last 30 years, from 61.5 kg per capita to about 85.9 kg per capita (milled rice) we can assume that the introduction of tools such as SMART-PADDY offering an increase productivity will revert in an increased food security and production, assuring the source of food for the growing world population.
In addition to the socio-economic benefits, the SMART-PADDY system offers also environmental profits. Firstly, it will optimise water usage by suggesting when it is advisable to water to reduce the effects of salinity in rice paddies leading, in some cases, to irrigation water reduction. Secondly, it will reduce energy usage from pumping stations: by monitoring the salinity of irrigation water it will be possible to determine when saline water is intruding the water table or river and therefore when it is not recommended to turn on the pumping stations. Thirdly, the intrusion of salty water will be reduced if irrigation is controlled under salinity parameters. This will reduce the irrigation in times when water is saltier and thus it will reduce the possible contamination of the water table or river. Finally, the concept of smart and sustainable agriculture will be enriched by the usage of SMART-PADDY. This will stimulate the consumption of “greener” products in the market and will have a positive effect on the environment and in the rice growers.
Finally, the SMART-PADDY sensor technology can be exported to other economic sectors such any industrial process demanding EC measurement or corrosion detection in submerged elements. This could be done by the SMART-PADDY sensor and would definitely become a major source of profits for the owners of the system will offering an improved productivity and yield to those sectors using the SMART-PADDY technology.
Main dissemination and exploitation activities
As previously discussed, the foreground generated by the SMART-PADDY project is broad and covers the whole supply and value chain and gives rise to potential exploitation opportunities for each member of the consortium. Each partner has expressed its intentions and wishes for the exploitation strategy. In addition, it allowed a great deal of dissemination activities to be carried out.
The current status of the protection and exploitation strategy for the SMART-PADDY foreground within the Consortium can be summarized as follows:
- A patent process related to SMART-PADDY to be commenced by 2 of the participating SMES (OSV and BEGAS) as described in the Joint Exploitation Agreement.
- The end-users SMEs (are willing to have preferential access to the technology for using it in their rice paddies.
- An industrial SME (LNL) is willing to have the role of the supplier for components of the system given their professional activity.
All these roles and strategy are defined in the Joint Exploitation Agreement signed by all partners.
A really successful dissemination strategy has been carried out during the SMART-PADDY project maximising the exploitability of the material and demonstrating its potential to provide rice growers a tool for remotely managing salinity and irrigation in their fields and thus increasing productivity and quality of rice.
Over the course of the project a total of 1160 interested people were directly contacted by the SMART-PADDY Consortium members in conferences, trade fairs, personal meetings and workshops. Moreover, a larger number were indirectly aware of the SMART-PADDY project via 5 press releases in the general media, 1 radio interview and 1 article published in a scientific publication. The details can be found in the list annexed or in the Part A of the PUDF.
The project has attracted a large interest from the rice-growing and scientific community and has been in contact with other FP7 projects to find synergies and evaluate the possibility of uniting the different developed technologies to provide farmers with a unique, complete tool.
List of Websites:
www.smartpaddy.eu
Contact details:
Mr. Pau Puigdollers
IRIS Innovació i Recerca Industrial i Sostenible, Spain
ppuigdollers@iris.cat
The SMART-PADDY project developed an on-line wireless sensor network capable of measuring electrical conductivity (EC), and thus salinity, in rice paddies, drainage or irrigation channels. This system is capable of substituting the expensive handheld meters used currently in the field and can be used to measure the salt content of the water used for watering the crops in a remote and accurate way. Indeed, the SMART-PADDY system can measure electrical conductivity by measuring electrical impedance in a range between 0.3 to 6.0 dS/m with an uncertainty of ±0.5 ºC. One of the most important features of the system is its ability to provide remote readings of the salinity in rice fields in a timely manner. Rice-growers have been able to read their salinity online using a tailored user interface which graphically represents the online readings in the field that are transmitted wirelessly from the field to the database. The functioning of the SMART-PADDY system has been proven to withstand the harsh environment of rice paddies and offer an extra functionality based on a novel development: it is capable of detecting biofouling or electrode corrosion which may alter the EC readings. In this way, the user can detect a misreading caused by an alteration on the electrodes and amend this problem in the field in spite of obtaining false EC readings.
The SMART-PADDY system is composed by autonomous nodes containing one (or up to 3) EC sensor(s), a communications module and an energy harvesting unit made of solar panels; a gateway receiving the readings of all nodes in the area and storing the information on a local database while uploading it to the cloud; a user interface displaying the information coming from the field.
SMART-PADDY was tested in 4 different rice cultivation areas in Europe and proved to provide valuable information to all of them. It was installed in rice paddies measuring water salinity at nearly root level, in an irrigation channel and in a drainage channel. This allowed to enhance the management of the water flooding in the paddies but also to improve the management of pumping stations in channels and to detect sea water intrusion. It was demonstrated that the SMART-PADDY system is able to provide the same accurate information than a high quality handheld meter while allowing a real time, remote and user friendly monitoring of this information. This functionality was proven to work for managing salinity in rice crops and therefore increasing the yield and optimizing the physiological characteristics of rice.
The SMART-PADDY system that led to the beginning of a patent process delivered tailored information to the rice-growers but could be used in many other industrial applications as electrical conductivity is a parameter commonly used in many sectors.
Project Context and Objectives:
Rice is the main crop in wet areas such as river deltas and is an essential tool in Europe in managing protected ecosystems. Irrigation water is a key factor in the production of rice and water quality has a major impact on crop yield as a result of tolerance of rice to factors such as dissolved salts. Rice is more water consuming than many other crops; in continuous flooding cultivation it takes about six times the water required by wheat. Due to increased water use in coastal areas, the sea intrudes the water table and rivers, and seawater floods nearby fields during storms in the Mediterranean area. The result is increased water salinity, which reduces yield in rice crops and increases soil salinity. Nowadays, water condition is for the most part assessed by visual inspection of the crops and, when excess water salinity is suspected, fields are irrigated by flooding them. In areas where water salinity is endemic, rice paddies are continuously irrigated with river water to reduce water salinity. This is a remedial solution that requires enormous volumes of water and considerable energy to pump water.
Water salinity can be accurately determined by measuring its electrical conductivity (EC). Measuring EC at the water inlet and outlet of each paddy field can help in monitoring the “washing” effect of irrigation. Moreover, measuring EC at points far from water inlets and outlets can help in assessing water salinity in a given paddy field and at different depths in drainage channels can help in managing water salinity in larger areas.
Based on this background the SMART-PADDY project developed a wireless sensor network comprised of low-cost EC measurement nodes and an autonomous power supply based on energy harvesting, that is capable of transmitting readings of water salinity in paddy fields in real-time to a central server. This data, accessible via internet, enables cultivators to effectively manage and protect their paddy fields and greatly reduce flood water consumption. Initial tests were made in the laboratory and the system has been validated in four different field set-ups, which proved the correct functioning of the system at various key locations in rice paddies.
The overall objective of this project will centre on the development of smart on-line water salinity measurement network to manage and protect rice fields that will be based on a wireless sensor network (SMART-PADDY) comprised of low-cost EC measurement nodes and an autonomous power supply based on energy harvesting, that will be capable of transmitting readings in real-time to a central server.
Firstly, the needs and specifications of the rice-growing industry were defined to drive the requirements of the different parts of the system. These included probes with 10-15 cm in diameter, 1m water resistant, IP67 or IP68, transceiver working at 433 MHz ISM band with up to 10 dBm power and at least, -110dBm sensitivity, less than 25 mA in receive and transmit mode, 10 MHz processor speed microcontroller with 32 KB memory and sensors ranging from 0.5 to 5 dS/m with 0.25 dS/m uncertainty and 0.01 dS/m resolution withstanding temperatures from -10 ºC to +60 ºC. The system should be solar powered and with external communication capability. The user interface should show graphs on the mean readings in the field, graphs for one specific node and possibility to select periods of time to be graphically represented.
Laboratory research conducted during the project showed that pulse wave excitation (PWE) and electrical impedance spectroscopy (EIS) are successful methods to determine EC in water. The developed sensors offered EC measurements based on these two methods to achieve a measuring range of 0.3 to 6 dS/m in an automatic temperature compensation (ATC) range of 5 to 35 ºC. The sensors were composed of a flat two-electrode EC cell based on two AISI 316 stainless steel acorn nuts with a PVC plastic body and volume delimiter to ensure a repeatable cell constant. The built sensor was based on the user needs and represented a low-cost, novel –and patentable – EC sensor.
An on-line wireless system for the measurement of salinity was designed and developed based on the requirements defined initially. This wireless sensor network (WSN) comprised independent nodes with Radio Frequency (RF) technology that communicated with a gateway device which gathered all data coming from the sensors and stored it locally and in a web server. The WSN was optimised in terms of distance of communications and power consumption to meet the overall requirements of the system.
The newly developed sensor and WSN systems were integrated into a single unit which comprised the SMART-PADDY system. Two new PCBs were designed (one for the RF and the other for the multiplexing and power management) following the research and tests performed previously. The best solution in terms of design simplicity were chosen in order to obtain an easy to assemble and disassemble device. A PVC encapsulation was designed which offered the required water proofing capabilities. The system was built to allow laboratory testing with a final set-up. An accessible web interface was also developed to show the data obtained in the field in a graphical and understandable way as the front-end of the SMART-PADDY system.
Laboratory and parallel field testing was carried out in order to validate the proposed SMART-PADDY system. The nodes were able to withstand the harsh environment found in rice paddies while the sensors offered excellently accurate EC measurements while the WSN managed to retrieve all data and store it locally and in the internet. The user-interface was perfected following the recommendations from the end-user SMEs to represent data in the most user-friendly possible way. A validation plan was put in place to evaluate the effects of the SMART-PADDY system in irrigation management and therefore on the physiology and quality of rice. Recommendations for future improvements to obtain a fully commercial version of the system were outlined.
The SMART-PADDY system proved to be an accurate and reliable tool for the management of rice paddies and improving the quality of rice. The close monitoring of salinity during the cultivation stage allows for a better regulation of irrigation and thus improves the quality and yield of rice.
The process of validation of the SMART-PADDY system took place in the 4 locations of the end-users SME partners in the project and involved the testing of the system in rice paddies (Greece), irrigation channels (France and Seville) and in drainage channels (Ebro Delta). This testing at different sites of a rice area allowed to evaluate the versatility of the system and to demonstrate the SMART-PADDY performance and features both within the consortium and beyond to a large number of industry stakeholders from the rice-growing sector.
While developing the SMART-PADDY technology, concern was also given to the cost of selected materials and components to guarantee the future exploitation of the SMART-PADDY system by keeping it of sufficiently low cost to ensure its uptake by the rice growing sector. The developed system cost is around the 2000€ per complete unit (including a sensor, gateway and software) which is in the range accepted by rice growers for such a device.
The overriding goal of this project was to ensure that the resulting pre-competitive SMART-PADDY prototype fulfils the set requirements to ensure its further development post-project into a fully industrial system that is taken to market, where its beneficial environmental and socio-economic impact will be felt at European level.
Project Results:
The main technological result of the SMART PADDY project has been the demonstration of the feasibility of an affordable, real time system able to monitor the electrical conductivity (EC) of water in rice paddies as surrogate for water salinity and its effectiveness in protecting rice plants. This is a leap forward in water management and precision agriculture as no wireless EC sensors were available in the market and the existing sensors are too expensive for multiple units to be installed over a large area. This result has implied several technological achievements and has established a clear advance in measurement science. In order to describe the specific results, the ten initial scientific and technological objectives of the project, are summarized below:
1. To research the needs and specifications of rice cultivators and use findings to define the specifications for the SMART-PADDY system.
2. To carry out research into the electrical conductivity sensors that will be effective in continuously measuring the salinity in paddy fields.
3. To develop the telecommunication system to ensure the effective transmission of data from the SMART-PADDY sensors in-field to a remote data repository.
4. To research the energy consumption of the system in order to ensure up to two years autonomous operation.
5. To integrate and test the system at laboratory level.
6. To design a flexible, easy to use, data-driven web-interface and back end software in order to process the retrieve data, as well as control instructions from operators (WP4).
7. To install the system in the field and to carry out trials with the SMART-PADDY system in a real field environment and to validate the performance of the system.
8. To study the salt effect on the physiology and quality of rice by carrying out rice agro-physiological trials and analysis, such as yield, salt injury, photosynthesis, K/Na ratio and quality.
9. To carefully outline recommendations for future development work for full commercial system.
10. To facilitate the uptake of the SMART-PADDY results by the participating SMEs, as well as a wider audience of rice growers, a comprehensive series of demonstration activities will be carried out that will showcase the performance of the prototype for measuring water salinity in PADDY-FIELDS, and communicate its benefits for water consumption, yields, economic returns and environmental protections.
The research of the first objective confirmed that current technology cannot provide the real time information offered by a system such as SMART-PADDY. It also confirmed the clear disposition of the industry to invest into new and innovative technology for improving the quality of their products and optimizing the water use. The industry consultations also provided valuable information regarding the frequency of measurements, the periods during the rice growth process where salinity measurements are more important and the measurement accuracy required for limiting yield losses. This information was taken into account for the definition of the SMART-PADDY specifications.
The research of the first objective also led to the identification of at least three different scenarios: salty irrigation water and normal soils, salty soils and quality irrigation water, and salty soils and water. EC sensor placement depends on the case. When only water is salty, it can be measured at water pumping stations or main irrigation channels. When only soil salinity is high, paddy water conductivity must be measured. Further, EC measurement at different depths in drainage channels can provide information about large areas and help in deciding when to increase the drainage flow by increasing the volume rate of pumps that empty channel water. The acceptable sensor node cost is much lower in paddies than in the two other cases and the EC sensor of SMART PADDY has been designed according to this most restrictive case.
The second objective of the project was the research and development of an EC sensor able to continuously monitoring water salinity in inundated paddy fields while fulfilling the low acquisition and maintenance costs required by stakeholders. EC sensors comprise an EC cell and the interface electronics to obtain the desired data. Usually, low cost EC sensors use two electrodes instead of four and must operate at a frequency high enough for the electrode impedance to be negligible as compared to water impedance. For high water conductivity, this implies measuring at a high frequency but then cable capacitance becomes important and contributes to the result. In order to avoid this effect, electronic circuitry can be placed next to the electrodes so that no cables are required between them, but even by so doing there is no guarantee that electrode impedance will not affect the result. This is because electrode material must withstand a saline environment, hence must be corrosion-free, and these materials do not necessarily establish a low impedance interface when immersed in saline water. Further, soiling and biofouling affect electrode impedance, which makes it still more uncertain which frequency to measure at in order for the effect to be negligible.
In order to solve this problem a novel approach to two electrode impedance measurements has been conceived: instead of trying to avoid electrode impedance, the overall impedance between the two electrodes is measured and then a procedure is devised to identify the respective contribution of electrodes and water to that impedance. This identification requires a method to distinguish both impedances.
It turns out that electrode impedance can be modelled by a resistance in parallel with a capacitance, which values depend on the frequency on the current through them, whereas below, say, 1 MHz, water can be modelled by a resistance. Overall, the measurement cell can be modelled by a simplified Randles circuit, which includes only three components, normally identified by measuring at three different frequencies, or at two different frequencies if the real and imaginary parts of the impedance are simultaneously measured. Those two or three frequencies must be apart enough for the respective measured values to be different without requiring very high resolution, which is very difficult to obtain in a low cost sensor. But in any case, solving the resulting equation system asks for computation resources unavailable in a low-power, low-cost system.
Prior art to overcome the need for measurements with sine waves from different frequencies is to inject voltage or current pulse waves into the measurement cell and then measure the resulting current or voltage at three different points and solve the equation system based on the ideal pulse response of the simplified Randles circuit. But, on the one hand, this does not overcome the need for solving an equation system, now with exponential functions, and on the other hand, actual pulse response includes transients attributable to parasitic impedances, particularly just after the leading edge of the pulse has been applied, and it turns out that the initial response value after the pulse has been applied has the information about water resistance.
During laboratory experiments to evaluate alternative circuits for impedance measurements based on pulse waves, a novel method has been developed to reduce those transients by reducing the slew rate of the leading edge of pulses. This method, however, cannot be directly applied when pulses are generated with low-cost microcontrollers.
A detailed analysis of the equivalent measurement circuit, later confirmed by laboratory experiments, revealed that the imaginary part of the EC cell impedance was due only to the electrodes. This lead to the following method: measure with a 100 Hz sine wave in order to inform about electrode impedance, hence electrode condition, and measure with a voltage pulse wave to determine water conductivity regardless of electrode condition. To avoid errors because of transients that can affect the initial value of the pulse response, two samples are taken at particular times after pulse injection and the initial value is calculated by an original interpolation method based on analytical properties of exponential functions, which performs better than linear interpolations described in some patents. The joint use of a low-frequency sine wave and a voltage pulse to measure liquid conductivity and at the same time assessing electrode condition is novel and patentable. Liquid conductivity is measured in many industrial and environmental applications other than water management in paddy fields. Overall, this approach to two electrode impedance measurements is a definite contribution to measurement science.
To achieve the low cost required for electronic circuitry to measure the impedance of the conductivity cell, and water temperature (required to compensate for the temperature coefficient of water conductivity, a low-cost microcontroller unit (MCU) that integrates 12 bit ADC and two DACs, and an analogue input multiplexer was selected. A previous uncertainty analysis demonstrated that 12 bit resolution (and ADC uncertainty for common MCUs) was enough to meet system specifications. This implementation of pulse-based impedance measurements by using a common MCU is a relevant technological result.
To reduce the analogue hardware between the EC cell and the MCU, there is no analogue demodulator to measure the real and the imaginary parts of the impedance. Instead, quadrature synchronous sampling is used, which implementation by a low-cost microcontroller is another relevant technological result because it leads to the design of compact, low-power, low-cost Electrical Impedance Spectroscopy (EIS) systems. In fact, SMART PADDY nodes measure impedance also at 83.3 kHz for redundancy. Further, the water temperature sensor is directly connected to the MCU without any intervening active component, which also reduces cost, power consumption and components number, hence improves reliability.
The design of the EC cell is also original. Low cost forbids the use of expensive materials or assembling techniques. Here it was decided to use a single EC cell design for the three different EC probes required to measure water conductivity at each of the three different scenarios identified. After several laboratory tests with saline water, it was decided to use Grade 4 (AISI 316) stainless steel acorn nuts (and bolts, common marine hardware) as electrodes and PVC for the body of the EC cell. A PVC volume delimiter determines the path of electric currents hence making readings independent from the closeness of the sensor to walls or to paddy bottom, and also from water movement. Overall, this design provided a highly repeatable cell constant for the 5 units built for the preliminary field tests of the first year and the 10 units built for the field tests of the second year.
The automatic temperature compensation (ATC), which is a required feature for all autonomous EC meters, has been designed to rely on a temperature sensor that is not in direct contact with water. Instead, the temperature sensor is placed on the internal side of the bottom of the EC cell. This temperature measurement, together with the measured impedance, permits to identify water absence and inform about that condition.
Finally, meeting discussions showed that it was convenient that sensor nodes retained the data logging capability designed in the EC sensor for the preliminary field tests and external communication features that allowed the EC sensor to be diagnosed even if it was not connected to any transceiver. This can be of help during manufacturing and troubleshooting.
The third objective concerned the telecommunication system to link the SMART-PADDY sensors to a remote data repository. Initially, a MESH (Multipoint Enhanced Signal Handling) of nodes was expected to be used, but none of the three scenarios required it. The adopted solution in the end comprised Radio Frequency (RF) communication between the sensors and the Gateway in the unlicensed 433 MHz ISM band but no need of communication between nodes was required although the protocol was studied and developed in case it was needed. The selection of this transmission frequency was made according to the price and capabilities criteria. In the market there are several ISM transceivers available which are cheap and at the same they offer important features like high sensibility, low power consumption and programmable transmission power. This satisfied two important requirements of the SMART-PADDY system: it offered low-cost Electrical Conductivity sensor nodes and an autonomous functioning over a long period of time. Moreover the use of the ISM 433 MHz frequency allowed the implementation of a small-sized antenna that can be easily embedded in the sensor node mechanics. The gateway was the central device gathering all the data coming from the sensors and storing it locally while uploading all information to the cloud server. It was formed by an Alix 3d3 embedded PC system board with an RF transceiver and a USB modem. It used UMTS/GPRS or Wi-Fi protocol to communicate externally with the cloud server.
As for the power supply system, which was the fourth objective, sensor nodes are supplied from solar cells as initially planned. They take less than 30 % of the top surface of the probes, which external diameter is less than 9 cm. This way, those cells are inconspicuous and do not attract vandals. In the first sensor prototype, the low supply voltage selected (3 V) was not enough to obtain the desired performance of the MCU so that it was raised to 3.3 V. Energy harvesting and power conditioning worked as required, the main problem being their installation in drainage channels because it may be convenient to rely on existing civil engineering works (bridges or concrete walls) but this may imply that solar cells remain several hours in the shadow. In these cases it could be advisable to split the probe in two bodies instead of using a single rigid body. Then the part with the transceiver could be fixed on a surface with a convenient orientation for solar energy harvesting whereas the part with the sensors must necessarily be immersed into the channel. Nevertheless, it must be considered that in all field tests a reading per hour was taken and communicated, that in some cases, particularly in drainage channels, was too high, as demonstrated by the large amount of repetitive readings obtained. If measurements were transmitted only three or four times a day, no special precaution for solar cells orientation could be necessary.
System autonomy in the proposal was expected to be two years. End users, however, informed that field probes would normally be retired before harvesting, which offered an opportunity to replace batteries if required. In practice, energy harvesting relies on secondary (rechargeable) batteries that can last for many charge-recharge cycles. Therefore, besides the convenience of retrieving probes to avoid any damage from or to rice harvesting machinery, no actions are required other than replacing degraded electrodes or EC cell calibration. Nevertheless, field tests have shown no effects from electrode soiling and fouling on EC measurements neither did EC cells need any calibration after cleaning them with tap water.
The fifth objective was to integrate the system and test it in the laboratory. Sensor probes that include a single EC cell comprise to printed circuit boards (PCB): one with the EC sensor electronics, next to the electrodes in the EC cell and another one close to the top of the probe that includes the control unit, the transceiver, and the energy harvesting and power conditioning circuits. Probes with the EC sensors include a PCB for each sensor and a single control and communication unit (CCU). Power and signal communication between EC sensor(s) and the CCU is performed through a custom-designed hub that is embedded into the CCU PCB. This substantially reduces the number of cables between both units and it is a solution that can be applied to other autonomous sensor nodes.
In order to reduce software complexity in sensor nodes and to avoid the need for any changes derived from possible communication system updates, all calculations required to obtain water conductivity from the measured resistance and for temperature compensation are performed in the server rather than in local processors or the gateway. Similarly, sensor calibration is performed via web so that there is no need to disassemble and reassemble probes.
The body of the three EC probe types is based on common (non-pressure) PVC piping hardware to reduce assembly costs. Both the EC cell, during the preliminary field tests of the first year, and the three different probes during the field tests of the second year have performed correctly. There were no water intrusion problems or cable disconnections in spite of their transport and installation. The system comprised a modular design in which the electronics could be assembled and disassembled without major difficulties and with no connectivity issues. The conductivity sensor was embedded in the lower cap of the mechanical design and had a constant volume cell around it which was secured with nylon bolts. The antenna and the PV cell were located in the top part of the probes. The antenna was held inside by a nylon screw while the solar cell was on top of the top cap where received the necessary sunlight. To ensure the waterproofing of the system, three piece systems with rubber joints were used in those parts where the water was in contact with the probe.
The sixth objective was the web interface, which was implemented using open-source web technology. The user interface system was based on MVC (Model-View-Controller) concept that isolates database with its processing (the Model) from the data manipulation (the Controller) and presentation of the data in web based user interface (the View). The model layer (where the database belonged to) defined the business logic of the system. The Controller system software architecture was a piece of code that called the Model to get some data that it passed to the View for rendering to the client. All requests were managed by front controllers. These front controllers delegated the real work to actions that were logically grouped into modules. The View was what the user interacted with. This layer was mainly made of PHP templates, which allowed a rapid development of views which were compatible with any viewing device (PC, phone or tablet) and any web browser. The view part of the Smart-Paddy software was developed in "open-source" technologies. The languages and structures which were selected were a MySQL database with PHP and AJAX (Asynchronous JavaScript and XML). As a data-interchange format inside the system JSON (JavaScript Object Notation) was used. It is a lightweight format, is easy for humans to read and write and for computers to parse and generate.
The designed web-user interface was refined and tailored to the end-users recommendations and needs to offer a user-friendly and useful system to understand and analyse the data coming from the field sensors.
The seventh objective was field installation and trials. The four installations were smoothly performed. Anchorages were adequate, did not require any special tools or skills, and withstood water and wind force and rain. Probes could be retrieved at the end of the season without any damage. Trials could be performed for more than four months in paddy fields, enough to monitor them during a complete rice-growing season, and for more than two months in water channels and pumping stations, which was also long-enough to assess system performance. A minor handicap was that 2013`s season was especially good in the four places and only a few high-salinity events were detected. No-water conditions were easily detected from the data obtained.
EC and water temperature readings from the SMART PADDY system were compared to those of commercial handheld EC meters and the correlation was very good, even for EC values below the specified range (0.5 to 5 dS/m). Conventional cultural practices, such as use of agrochemicals, have not interfered with system operation in the EC or temperature measurements. Sensor nodes close to high-power equipment such as water pumps were not affected by electromagnetic interference.
Electrodes during field experiments could not be continuously monitored by visual inspection. In order to ensure that EC measurements performed after long-time immersion were good, changes in electrode impedance during continuous water immersion were monitored for 70 days in a separate laboratory experiment. Changes in electrode impedance did not affect the water conductivity value measured. This validates the proposed measurement solution. Electrodes in the retrieved probes were not so affected by biofouling as those in the water tank in the laboratory, exception made of that in the drainage channel.
The eighth objective concerned the trials and analysis of the effects of salt on the physiology and quality of rice. Analysis of the four different treatments applied in the experimental rice paddies in Greece confirmed that salinity levels that result in EC > 3 dS/m during the 20 first days after sowing reduced yield and many agronomic and quality characteristics of rice. This is important because it implies that areas with high soil salinity need prolonged irrigation to wash away excess salt. That salt may be a result of sea intrusion and lack of irrigation during winter, but also from practices to combat some pests that consist of irrigating fields with salty water in winter. The SMART PADDY system can help in determining when salt has been sufficiently washed away before sowing, in addition to monitor paddy water salinity during all growing season.
Analysis of the harvested rice showed that the following traits were affected by salt toxicity: height, chlorophyl concentration index, tillering, dry matter accumulation, spikelet length, dehusked length, width and their ratio, 1000 grains weight, whole milling yield (breakage of the grains during the milling process), Na and Na/K ratio.
The ninth objective aimed at outlining recommendations for future development work leading to a commercial system. Laboratory tests, preliminary field tests, field trials in four different places to fulfill the requirements of four different scenarios, technical and general steering committee meetings and demonstration sessions where interaction with possible users was direct provided plenty of information about improvements to be considered in a design review, technical features that could be easily added and possible applications not initially considered.
These future improvements apply either to all uses or only to particular uses, the main difference being whether sensor nodes are to be installed in paddies or on channels, and in this second case, on whether they carry a single water conductivity sensor or several (up to three) sensors. In general, design provisions included to enable field testing by an expert technician would not need to be included in a commercial product because, on the one hand, information about internal status can be made available to technicians via web and, on the other hand, it would be easier to replace malfunctioning probes than to repair them in situ. However, data logging capability in the gateway is instrumental to retrieve information when the internet connection fails, which is not an unusual event. Similarly, when several nodes are used in a relative large area, which increases de risk of failed connection to the gateway, keeping the data logger feature in each node, as designed for the preliminary field tests, could be convenient and will not require any hardware modification.
All applications would benefit from an alarm about possible wrong water temperature measurements, which implementation would be easier if the sensor that measures air temperature inside the (bottom of the) probe is kept in future designs.
In probes with a single sensor, those for paddies or water pumping stations, the transceiver unit could be directly connected to the EC sensor unit in the probe, i.e. the no hub for power and data communication is required. To cover sensor-gateway distances that exceed the available RF range, a new type of “relay node” could be designed that includes only the power supply and the transceiver if that node is to be placed outside a paddy field.
With regard to the mechanical design of the probes, it would be convenient to have a means to ensure that electrodes in the EC cell are really perpendicular to the windows of the cell, instead of relying on the criterion of the person that assembles the probe.
The gateway could be programmed to accept signals from other sensor nodes that measure different quantities, related to rice cultivation or not.
In order to implement Electrical Impedance Spectroscopy based on sine waves by using the technology used in SMART PADYY, it would be convenient to modify the timing of measurements performed with high-frequency sine waves in order for some transients to extinguish down before signals are sampled. The specific changes required are described in Section 2.1 of Deliverable 5.3.
Objective 10 targeted the uptake of the SMART-PADDY results by the participating SMEs and the larger rice-growing community in the participating countries. To this end, 3 demonstration activities were planned and carried out in Greece, France and Spain. The first one, held in Chalastra, Greece on the 25th April 2013, gathered 33 attendees comprising rice growers, millers and agriculturists. The demonstration showed the functioning of the system and its installation. The session was filmed and the feedback questionnaires gathered from the attendees reflected a high satisfaction among the participants. The second demonstration activity, held in Chamone pumping station, Arles, France on the 28th June 2013 gathered the 8 participants among which there were the farmers using that pumping station and two agronomy students. The demonstration showed the working system in the field, and many issues were discussed during the session. The third demonstration activity was held in Ebro Delta, Spain, on the 18th September 2013 and gathered 6 rice growers and the participants of the European Project RICE-GUARD (606583). The session showed the installed system working in a drainage channel measuring salinity at 3 different heights and data shown in the user interface in real time.
The demonstrations served to show the rice growing community of the participating countries together with relevant stakeholders the correct functioning of the SMART-PADDY system to promote the interest of farmers across Europe. This objective was fulfilled completely by completing 3 demonstration activities and obtaining valuable and positive feedback from the rice-growers.
The SMART-PADDY system serves the purpose it has been developed for. It is a low-cost system able to continuously monitor water salinity by measuring electrical conductivity of water in rice paddies, irrigation channels, pumping stations and drainage channels. Therefore, it provides an excellent tool for irrigation water management either for individual farmers or for farmer cooperatives or other associations. It can also be used as a research tool to study the effect of paddy water salinity on rice yield and quality. In this regard, it is worth to consider that in some cultivation areas outside Europe, irrigation water available does not normally have good quality, which is different from the scenarios here considered where irrigation water had excessive salinity only at particular times of the day or season.
Potential Impact:
There are numerous socio-economic impacts that will be derived from the results of this SMART-PADDY research project.
Central to the expected socio-economic impacts is the boosting of the competitiveness of rice farmers and companies along the rice value chain- by improving the crop yield and quality. Since the reduction of the intervention price for rice by 50% in 2004, the rice sector has had to readjust to become more competitive in front of the Asian market imports. Overall, the European rice sector faces a delicate situation and needs to benefit from any technology or system capable of enhancing their yield and therefore overall income.
Despite prices of rice falling back from the average prices in 2008 and 2009 they remained well above historical price levels, with the price in 2010/11 being between 61% and 71% above the values of 2006/07. In 2011 the global trade of rice reached record levels and prices were around 22-23% higher than those of 2010. These figures suggest a considerable price volatility on global rice markets and reflect a strong dependence on climatic and weather related factors. This means that any system capable of controlling the natural variables of rice production –such as salinity, will be a very valued technology by the rice-growing sector. This need is enhanced by the fact that the trends in the EU show that the consumption is growing faster than the domestic production, therefore imports are larger and include varieties of rice not grown in the EU. Thus, EU rice growers are in need to increase productivity and yield and the rest of the rice-growing continents need to ensure a stable and productive activity in order to meet with the needs of the market. SMART-PADDY can help fulfil these needs across the global rice-growing community.
Taking into account the economic aspects and the benefits for the rice growing industry by achieving for example a reduced irrigation water consumption or an increased time management, SMART-PADDY technology is expected to have a significant impact on the rice growing industry, which is demanding of such improvements to reduce irrigation water usage, production costs and enhance crop yield, and will therefore have a direct positive effect of the environment.
Moreover, the impact of SMART-PADDY will not only affect EU rice-growers, but it can have a global effect on the worldwide rice growing community. Production is geographically concentrated in Western and Eastern Asia with more than 90 % of world output. China and India, which account for more than one-third of global supply over half of the world's rice. Brazil is the most important non-Asian producer, followed by the United States. If the SMART-PADDY system owners (OSV and BEGAS) manage to commercially exploit the system with a global patent, the sales could boost to all the producers across the rice-growing countries. This would imply a large benefit for the participating SMEs while ensuring an improved management of salinity in rice paddies worldwide.
The economic impact associated to SMART-PADDY will expand to several sectors across the value chain apart from the rice-producing end-users:
i) Producers of raw materials, components and equipment:
The electronics producers will benefit from the demand of components for the SMART-PADDY system which will require the elements for the EC sensor system, the hub and energy management system and the RF transceiver system together with the solar cells for energy harvesting. Moreover, the PVC producers and suppliers will also have to provide the necessary elements for the mechanical housing of the probes.
ii) Manufacturing and distribution companies:
The manufacturing companies will have to produce and program the SMART-PADDY hardware and software and deliver an off the shelf package for the final retail or industrial agricultural companies to distribute the system to the end users. This will increase their activity and number of orders and in return increase their profit substantially.
iii) Agricultural machinery suppliers
The responsible companies for delivering the SMART-PADDY system to the final users will be those dealing directly with rice-growers, mainly supplying the agricultural tools needed for their operation. They could also be supplying the novel SMART-PADDY system as an innovative tool for the rice-growing communities and therefore increasing their share of sales and support and in return, their benefits.
The increased productivity and growth generated by the more accurate control of salinity in irrigation water will directly affect the job creation and rural employment, offering a social benefit to the SMART-PADDY system. In areas where rice is cultivated it is often the only source of income of the communities inhabiting those zones and therefore tools such as SMART-PADDY will be welcome by all agricultural land owners and associations. Moreover, taking into account that rice provides 21 % of global human per capita energy and 15 % of per capita protein; that rice is the second largest produced cereal in the world while world rice consumption increased 40 % in the last 30 years, from 61.5 kg per capita to about 85.9 kg per capita (milled rice) we can assume that the introduction of tools such as SMART-PADDY offering an increase productivity will revert in an increased food security and production, assuring the source of food for the growing world population.
In addition to the socio-economic benefits, the SMART-PADDY system offers also environmental profits. Firstly, it will optimise water usage by suggesting when it is advisable to water to reduce the effects of salinity in rice paddies leading, in some cases, to irrigation water reduction. Secondly, it will reduce energy usage from pumping stations: by monitoring the salinity of irrigation water it will be possible to determine when saline water is intruding the water table or river and therefore when it is not recommended to turn on the pumping stations. Thirdly, the intrusion of salty water will be reduced if irrigation is controlled under salinity parameters. This will reduce the irrigation in times when water is saltier and thus it will reduce the possible contamination of the water table or river. Finally, the concept of smart and sustainable agriculture will be enriched by the usage of SMART-PADDY. This will stimulate the consumption of “greener” products in the market and will have a positive effect on the environment and in the rice growers.
Finally, the SMART-PADDY sensor technology can be exported to other economic sectors such any industrial process demanding EC measurement or corrosion detection in submerged elements. This could be done by the SMART-PADDY sensor and would definitely become a major source of profits for the owners of the system will offering an improved productivity and yield to those sectors using the SMART-PADDY technology.
Main dissemination and exploitation activities
As previously discussed, the foreground generated by the SMART-PADDY project is broad and covers the whole supply and value chain and gives rise to potential exploitation opportunities for each member of the consortium. Each partner has expressed its intentions and wishes for the exploitation strategy. In addition, it allowed a great deal of dissemination activities to be carried out.
The current status of the protection and exploitation strategy for the SMART-PADDY foreground within the Consortium can be summarized as follows:
- A patent process related to SMART-PADDY to be commenced by 2 of the participating SMES (OSV and BEGAS) as described in the Joint Exploitation Agreement.
- The end-users SMEs (are willing to have preferential access to the technology for using it in their rice paddies.
- An industrial SME (LNL) is willing to have the role of the supplier for components of the system given their professional activity.
All these roles and strategy are defined in the Joint Exploitation Agreement signed by all partners.
A really successful dissemination strategy has been carried out during the SMART-PADDY project maximising the exploitability of the material and demonstrating its potential to provide rice growers a tool for remotely managing salinity and irrigation in their fields and thus increasing productivity and quality of rice.
Over the course of the project a total of 1160 interested people were directly contacted by the SMART-PADDY Consortium members in conferences, trade fairs, personal meetings and workshops. Moreover, a larger number were indirectly aware of the SMART-PADDY project via 5 press releases in the general media, 1 radio interview and 1 article published in a scientific publication. The details can be found in the list annexed or in the Part A of the PUDF.
The project has attracted a large interest from the rice-growing and scientific community and has been in contact with other FP7 projects to find synergies and evaluate the possibility of uniting the different developed technologies to provide farmers with a unique, complete tool.
List of Websites:
www.smartpaddy.eu
Contact details:
Mr. Pau Puigdollers
IRIS Innovació i Recerca Industrial i Sostenible, Spain
ppuigdollers@iris.cat