The SNiP-MP4 is a 'Sensor Node Integrated Package' for LoRaWAN or CAT-M1 communication of real-time accurate soil moisture measurements for continuous soil monitoring.
The base SNiP-MP4 integrates 1x MFR-NODE and 1x MP406 soil moisture probe to a site’s unique network, communication and power requirements. The MFR-NODE can support an added 3x MP406 soil moisture probes to monitor soil moisture at multiple depths.
The MP406 provides a measurement on the absolute Volumetric Soil Water % (VSW), based on the Standing Wave, or Amplitude Domain Reflectometry (ADR) measurement principle.
Alternatively, an extended SNiP-MP4 can be customised to include sensors that measure
Standing Wave, or Amplitude Domain Reflectometry (ADR), uses an oscillator to generate an electromagnetic wave at a consistent frequency, which is transmitted through a central signal rod, using outer rods as an electrical shield. The electromagnetic wave is partially reflected by areas of the medium with different dielectric constants (water content), producing a measurable voltage standing wave. ADR measures volumetric soil water (VSW%) independently of all other soil variables, including density, texture, temperature and electrical conductivity. ADR does not require in-situ calibration to accurately measure Volumetric Soil Water (VSW%).
Environmental, agriculture & engineering applications requiring assessment of the changes of soil moisture in absolute mm and the exact volumetric soil moisture use ADR or TDR technologies. ADR sensors that have been buried permanently in landfills are still functioning after 15+ years.
|ADR Soil Moisture SNiP||SNiP-MP4|
|SNiP Measures||VWC %|
|Core Sensor/Device (Measurement Principle)||MP406 (ADR)|
|Calibration||Mineral & Organic Soils|
|Sensors SNiP Supports||Up to 4|
|Mounting / Power||SPLM7 / 10W Solar Panel (SP10)|
|Optional SNiP Extensions of Parameters:||Tipping Bucket, Rain Gauge|
MP406 uses the standing wave principle of measurement. It is equivalent to a Time Domain Reflectometry (TDR) sensor without the need for a complex and expensive pulse generator. MP406 is a high accuracy, precision sensor with 1%VWC accuracy following soil-specific calibration and 0.01%VWC resolution.
The results from measurement of absolute volumetric soil water percent (VSW%) from prepared soil samples using the MP406 are given above (Figure 1). This result is typical of the results obtained from comparative testing of the MP406 in prepared soil samples, for a wide range of agricultural soils.
Standing Wave Technology and hence the MP406 are not affected by changes in temperature or salinity of the soil or material being measured and hence the values of VSW% are equivalent to oven dried water content.
The standing wave technique uses an oscillator to generate an electrical field in order to detect the dielectric properties of a substrate of interest. The parallel needles of an MP406 act as a coaxial transmission line to generate a signal. The amplitude of the signal is related to the dielectric constant which in turn is directly related to moisture content.
The results from measurement of absolute volumetric soil water percent (VSW%) from prepared soil samples using the MP406 are given alongside. This result is typical of the results obtained from comparative testing of the MP406 in prepared soil samples, for a wide range of agricultural soils. Standing Wave Technology and hence the MP406 are not affected by changes in temperature or salinity of the soil or material being measured and hence the values of VSW% are equivalent to oven dried water content.
Linearisation tables can be added to Data Loggers using the following data:
Converting Data Table for MP406. From VSW% to mV & mA
|Soil moisture VSW%
The Multifunction Research Node has been designed to provide flexible communication, sensor and power options.
The MFR-NODE supports SDI-12 and 4 x dry contact digital inputs as well as 2x differential / 4x single ended analogue inputs. The MFR-NODE supports sensors with higher power requirements; a solar panel can charge either the internal lithium-ion battery or both the node and sensor can be powered by an external 12V system (e.g. battery or mains source). Optional CAT-M1 provides an option for remote installation in areas outside the range of existing LoRaWAN networks. The optional multiconstellation GNSS ensures you won’t lose track of your device. The MFR-NODE has an onboard 8GB SD Card to provide data logging capabilities and full data redundancy in the event of temporary loss of communications or dropped packets – ideal for research applications.
Measure volumetric soil moisture for scientific research, agriculture and civil engineering.
The MP306 has a compact body and the needles are arranged in a single plane making it ideal for use in soil columns. It is also ideally suited to measuring pots in glasshouses and growth cabinets. The MP306 can also be installed in the field, with a lifespan of 20+ years in the most extreme conditions.
|Measurement Range||0-100 VSW%|
|Accuracy||1% VSW% after calibration to a specific soil type
± 5 VSW% using the supplied soil calibration
|Response Time||Less than 0.5 seconds|
|Stabilisation Time||3 seconds approximately from power-up|
|Input Requirements||9-18 V DC unregulated|
|Power Consumption||24 mA typical, 30mA max|
|Output signal||0-1160mV for 0-100 VSW%|
|Total Length||210 mm|
|Needle Length||60 mm|
|Needle Seperation||12 mm|
|Needles||Stainless Steel (Grade 316) – does not corrode in saline solutions|
|Environment||Designed for permanent or temporary burial|
Traditional irrigation systems typically operate on a timer and do not respond to weather conditions or actual plant water requirements. Smart irrigation systems which are responsive to plant water requirements can optimise water usage, improve plant growth, and reduce nutrient leaching into adjacent water bodies.
For sustainable management of parks and lawned surfaces, it is important that the factors that influence changes in soil moisture content are understood and measured so that the irrigation conditions can be optimised to suit each location and the plant type. In 2019 the Cairns Regional Council, in conjunction with Central Queensland University, commenced the Smart Urban Irrigation Project with the aim of optimising irrigation via the integration of best available irrigation equipment, real time monitoring data and the latest irrigation software.
The project investigated various aspects that influence soil water content in Cairns parks, including soil properties, plant characteristics, weather conditions, and management practices, with the aim of developing a computer model that would help control irrigation in Cairns parks. Two parks, the Eastern Lagoon and Fogarty Park, were selected for intensive investigation. The grasses in these parks have shallow root systems (<20cm depth) due to compaction and low soil infiltration rate, and currently require frequent irrigation.
The researchers, Associate Professor Nanjappa Ashwath and Dr Biplob Ray, say that the data collected from this project will help minimise deep drainage so excess water and nutrients leaching into Great Barrier Reef can be reduced.
Following Dual EM and infiltration surveys, soil moisture content at each of the two parks was monitored at three locations, each broadly representing low, medium and high moisture zones. At each location 4x MP406 moisture sensors were installed at 10, 30, 90 and 120cm depths. The MP406 sensor was selected because of its capacity to measure VSW% accurately in the saline coastal soils.
The MP406 probes were supported by an MFR-NODE, which transmitted the data from each site over LoRaWAN to a solar powered gateway located on the rooftop of the CQUniversity in Cairns. Given the public nature of the site all monitoring equipment was housed in a subterranean junction box and battery powered. The 4G connection, gateway and nodes were administered using The Things Network (TTN) LoRaWAN server via 4G connection.
The interface has been set up to receive and translate LoRaWAN gateway signals in National eResearch Collaboration Tools and Resources (Nectar) Cloud which also hosts the Chronograf dashboard with the InfluxDB database to store, analyse, and manage the data. The Chronograf dashboard helps visualise the data and sends alerts based on events extremely low or high moisture content. The AI (Artificial Intelligence) powered brain of the system was also developed for automating the entire irrigation process.
Data (above) from dashboard showing how the MP406 sensors are responding to daily irrigation or rain on the 18th, 19th, 20th December 2019. The Data assisted the park manager with an ability to discern moisture content of selected soil layers (for example 10cm depth) so a decision can be made to judge if the park is under or over-irrigated.
This project was supported by Cairns Regional Council, the Australian federal Smart Cities Program and CQU’s Centre for Intelligent Systems.