Soil Moisture Monitoring

Application Notes

Application Background

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Soil Moisture Monitoring is used in agricultural water management applications such as irrigated fields, and in the turf industry for large grassed areas such as sports playing fields and market gardens to optimise the use of reticulation / irrigation system water usage. There is also a very large installed base in the viticulture industry. These systems may employ a range of different soil moisture sensors. The simple approach is to measure soil moisture directly and then decide on the best settings for a reticulation/ irrigation

Monitoring Industrial Overflow
Soil Moisture Monitoring - Turf

A more complex and more detailed approach is to measure Evapotranspiration (ET). ET is the most significant indicator to measure water movement for agriculture. ET refers to two processes: water loss from surfaces such as soil (evaporation) and water loss from the leaves of crops (transpiration).
The weather affects ET, solar radiation, air temperature, air humidity, and wind speed. But ET also depends on the nature of the crop, how it changes with time, and soil moisture levels. Evaporation and transpiration occur simultaneously and dependently, so are treated as one process. When a crop is first planted, the soil is exposed to the sun and most of the water loss initially is through evaporation. But as the crop grows and starts to shade the soil, evaporation decreases and transpiration increases.

Application Detail

For the simple approach single soil moisture sensors can be an older style of gypsum block, measuring resistance across that block or a modern sensor using Time Domain Reflectometery (TDR) techniques to send out a pulse and measure the return echo to determine the water / moisture content of the soil.

Soil Moisture Monitoring - Installation NEON Datalogger
Soil Moisture Monitoring - Installation

The soil moisture sensor is connected to a data logger or Neon Remote Module and a scheme / program is set up to measure, store, and optionally display soil measurement data locally, or routinely send that data via the internet to a Neon Server, so it can be viewed on a standard web browser. The data logger or Neon Remote Module can also be programmed to react to certain events. For example, if it has rained and the soil is very moist, the data logger could be programmed to signal an irrigation system that it did not need to run at that time.
The turf industry, especially those that operate on sandy soil areas has been slow to take up soil moisture monitoring. With recent advances in technology and communications, however, soil moisture monitoring is now a real option.

Modern soil moisture probes are reliable and affordable. Telemetry options mobile phone / cell phone and satellite network modems are also affordable, so moving data from the field to websites, and easy access to data on mobile Web Browsers and specialized apps on iPads and iPhones make it easy for Turf managers and Irrigators to check soil moisture reading in the field.

Soil Moisture Monitoring - Performance Demonstration
Soil Moisture Monitoring - Installation Datalogger Equipment

The Unidata partner, Future Turf produces a complete system. This turf irrigation tracker system is easy to of install and there is minimal disruption to the sports oval playing surface. The user gets instant collection and transfer of data through its “plug and play” nature and soil moisture data is well presented on easy to understand graphs either on an iPad or Laptop. It is also easy to relocate the probe if needed.

Soil Moisture Monitoring - Installation Works
Soil Moisture Monitoring - NEON Datalogger

The Irrigation Tracker generates important information for irrigation managers, such as confirmation of the amount of irrigation applied, monitoring irrigation depth, monitoring the soil moisture status of the root zone, monitoring root zone salinity and monitoring root zone soil temperature. The Irrigation Tracker components are securely housed in a standard valve box, or buried below the turf surface. A 40cm sub-surface probe with four sensors measures soil moisture, salinity and temperature at 10, 20, 30 & 40cm, The Neon Remote Module / logger stores data collected from the probe and sends that data back to a Neon Server daily. With a daily reporting period a battery pack can power the entire system for 2 years. For the more complex and detailed approach to measure ET we can estimate ET from meteorological data, but a far more direct, accurate and defensible measurement uses the ‘Eddy Covariance’ (EC) method. Instruments on the EC tower continuously and rapidly sample the turbulent airflow that transports water vapor, heat and carbon dioxide used, or given off, by plants during photosynthesis or respiration. This method is accurate, but complex, and to get good results, we pay detailed attention to specifics.
The EC tower uses the following sensors to telemeter several parameters needed to accurately calculate ET:

  • a sonic anemometer to rapidly and continuously measure turbulence in the air
  • a sensor/analyser to continuously measure the concentration of carbon dioxide and water vapor in the air next to the anemometer
  • a net radiometer to measure the difference between incoming solar radiation and radiation reflected back to the sky
  • a quantum radiometer to measure only that part of solar radiation that the plants use for photosynthesis, when they use carbon dioxide and water to grow
  • a pyranometer to measure radiation from sun and sky and air temperature/humidity sensor a heat flux sensor to measure heat flow into and out of the ground.

You can measure the water passing through the soil with lysimeters, located near the EC tower. Sites need careful preparation and require a significant amount of excavation to create two underground bunkers where the measurement equipment is housed.
You can use a containment vessel, or barrel, to isolate a cylindrical core of the crop along with the soil it grows in. You then reposition this, with the lysimeter opening at ground surface level, so it looks like and shares the same environment as the rest of the crop, in this case pasture. You can measure the amount of water leaching through the contained soil by piping it out the bottom of the barrel to a rain-gauge located below it in the underground bunker. You can then compare the amount of water that flows through the lysimeter (water out) with the rainfall or irrigation (water in) that we measure in another rain-gauge at the same location. You can also use more than one lysimeter at each site to measure soil moisture sensors at different depths within the barrel, to give a continuous representative vertical soil-moisture profile

Typical Configuration

Options for Application Specific Instruments / InputsUnidata Part NumberDescription
EnviroPro Soil Moisture and Temperature Probes6513GL-XXSoil Moisture and temperature probes with number of sensors from 4 to 12
Vaisala Weather Transmitter WXT536 measures barometric pressure, humidity, precipitation, temperature and wind speed and direction6501V-HVaisala WXT536 Weather Transmitter RS232/422/485 SDI-12 With Bird Spikes
Rain Gauge6506CRain Gauge / Tipping Bucket
Options for Neon Telemetry - NRT / RTU / Field UnitsUnidata Part NumberDescription
Cellular RTU 3G2013F-AB03Neon Metering Module 3G with Antenna and Li Battery
Cellular RTU 4G2013F-AB04Neon Metering Module 4G with Antenna and Li Battery
Cellular RTU 3G - Industrial2016F-AB03Neon Remote Terminal 3G with Antenna and Li Battery
Cellular RTU 4G - Industrial2016F-AB04Neon Remote Terminal 4G with Antenna and Li Battery
Low Earth Orbit Satellite Globalstar2015E-AB0Neon Remote Terminal - Satellite Globalstar Modem with Antenna and three Li Batteries
Ethernet2017E-0B0-1 or 3NRT Ethernet with single or triple Ethernet Ports
with three Li Batteries
Equatorial Orbit Satellite - Inmarsat2018E-AB0-1 or 3NRT Ethernet with single or triple Ethernet Ports
with three Li Batteries
LCD Display2500ENRT LCD Display
NRT Field Termination Strip2103F2015E,2016F,2017E, and 2018E NRT FTS
NRT Firmware Option2303A-8M8M Extended Memory Option
NRT Firmware Option2303A-8M-CAM8M Extended Memory & Serial Camera Option
NRT Firmware Option2303A-CAMSerial Camera Option
Options for Neon Application Software - Customer ServerUnidata Part NumberDescription
Neon Application Software2302ANeon Server Software Licence Incl 5 NAL
Neon Application Software2302A-10Additional 10 NRT Access Licences
Neon Application Software2302A-20Additional 20 NRT Access Licences
Neon Application Software2302A-50Additional 50 NRT Access Licences
Options for Neon Application Software - Unidata ServerUnidata Part NumberDescription
Neon Application Software2301ANeon Data Initial Subscription Setup Fee
Neon Hosting Service2301A-01Neon Data Service Fee for 1-50 NRTs
Neon Hosting Service2301A-02Neon Data Service Fee for 51-100 NRTs
Neon Hosting Service2301A-10Neon Data Service Fee Metering
Options for Conventional Dataloggers / Field UnitsUnidata Part NumberDescription
Standards Starlogger6004D-11Red Logger 512K with Alkaline Battery
Display Starlogger6004D-21Blue Logger 512K with LCD and Alkaline Battery
Prologger7001D-11Green Logger 1M with LCD and Alkaline Battery
Micrologger8010C-EURMicrologger 512K
Starlogger Field Termination Strip6103E6004D FTS
Prologger Field Termination Strip7100E7001D FTS
Starlog V4 Management Software6308A-AUEStarlog V4 Full Licence Key