Soil Moisture Sensors
Soil Moisture Sensors

Better Landscape, Less Water, More Savings with Baseline's Soil Moisture Sensors

Baseline biSensor Soil Moisture SensorUsing Baseline’s biSensor™ soil moisture sensors, you can create healthier landscapes and save time, money, and water in the process.  Baseline’s biSensor soil moisture sensors use patented technology to water better than any other technology on the market and biSensors save money because they reduce water usage—up to 62 percent or more over traditional irrigation methods.  They automatically self-adjust with the season, which means fewer trips to the field to adjust your irrigation controllers.  Simply put, you’ll love the results in your landscape and the savings of time, water, and money.
 

Baseline offers two different biSensors to meet your watering needs. The 15-inch original biSensor is ideal for in-ground applications, and water feature monitoring. The 3-inch compact biSensor is ideal for greenroofs, greenwalls, and containers. The biSensors differ only in their dimensions; otherwise, they both have the same operating features and operating specifications. Either biSensor can be used in any application.
 

Patented Reliability

Baseline’s biSensors use patented technology called Time Domain Transmission (or TDT), to measure volumetric soil moisture and provide the most sensitive, repeatable, and accurate readings from the most durable device available.
 

Sensitivity.  The biSensor is capable of measuring volumetric soil moisture changes of less than 0.1 percent.  biSensors are a powerful tool for natural and engineered soils alike. 
 

Repeatability.  Always get the right reading, regardless of changes in soil salinity or other factors.  biSensors give you unmatched confidence in your irrigation system. 
 

Accuracy.  Soil moisture readings are within ± 3 percent of the actual volumetric soil moisture content.   biSensors allow for the best possible irrigation decisions from an irrigation controller.
 

Durability.  The biSensor has a rugged design that will stand up to the toughest conditions.  biSensors will give you year after year of dependable service for your irrigation system. 
 

A Thermostat for your Landscape

A Thermostat for your LandscapeBaseline’s biSensors are as effective at irrigating your landscape as a thermostat is at keeping your home a comfortable temperature.  biSensors measure soil moisture levels where it matters, in the root zone of the plant.  Other “smart” watering methods, like weather-based ET systems, rely on environmental factors and a complicated mathematical formula to estimate how much water the plants need.  Plus, a weather-based system can’t measure the effectiveness of the decisions that were based on the complicated formula.  A Baseline biSensor automatically adapts to the effects of evapotranspiration in real-time. The bottom line—biSensors water better than any other irrigation system on the market. 
 

How it Works

How a biSensor WorksBaseline Soil Moisture Sensors work by sending a high frequency pulse of electricity down an embedded wire path.  The high frequency of the pulse causes the sphere of influence to move outside the sensor blade and into the soil around it.  When the pulse travels through moisture, it slows down.  The sensor measures the speed, and then converts this measurement to a moisture content reading. 

 

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Baseline's Soil Moisture Sensors — Features and Specifications

Features

  • Accurately measures soil moisture using patented modified TDT technology
  • Self-calibrates to all soil types and conditions
  • Soil moisture readings are within ±3% of the actual volumetric soil moisture content
  • Measurement ranges from 5% moisture to fully saturated soil
  • Capable of measuring changes of less than 0.1%
  • Measures soil temperature
  • Moisture readings are consistent in salty conditions
  • Sensor is completely sealed – no electrical contact with soil eliminates any electrostatic degradation or Galvanic corrosion of the sensing element
  • Power surge resistant
  • Shock resistant
  • Not affected by salts or fertilizers
  • Provides automatic and continuous measurements of soil moisture and soil temperature
  • Has true two-way communication using a 9-byte packet for commands and replies
  • Capable of self-identifying to the two-wire controller and will report pre-configured unique serial numbers
  • Has one pre-assigned serial number
  • Has standard error collision detections and will resend messages on the two-wire

 

Specifications

  • Sensor has no electrical contact with soil
  • Freeze/heat resistant -4oF to 140oF (-20oC to 60oC)
  • Can only be connected to Baseline controllers
  • Requires 3M™ DBR/Y-6 Direct Bury Splice Kit wire connectors on the two-wire side
  • Requires all connections to be installed according to manufacturer’s instructions
  • Sensor element is constructed of a multi-layer fiberglass stick
  • Comes with 50 feet of 18-gauge (UL) direct burial, dual conductor irrigation cable (voltage rating: 300V, temp rating: 167oF (75oC)) to connect to the two-wire
  • Has a built-in temperature sensor used while calibrating the soil moisture readings
  • Has a conditional five-year exchange warranty
  • Sensor logic module measures 2” x 3” x 1” 
  • BL-5311 Compact biSensor
    • Sensor blade measures 3.2” x 3.25” x .075”
    • Measured volume is 4.5 cubic inches, or 0.25” on either side of the sensor
  • BL-5315B Original biSensor
    • Sensor blade measures 14.95” x 2.25” x .075”
    • Measured volume is 12.96 cubic inches, or 0.25” on either side of the sensor

 

Installation Specifications

  • Keep the maximum wire run between soil moisture sensor and the controller the same as stated in the two-wire specifications
  • Connect the soil moisture sensor to the two-wire per manufacturer’s specifications
  • Install the soil moisture sensor in a location representative of the zones that the sensor is controlling
  • Bury the soil moisture sensor in an area of average water distribution between two sprinkler heads and place it on the centerline between sprinklers
  • Install the soil moisture sensor 2-3 inches below the surface of the soil or in the top 1/3 of the root zone
  • Bury the soil moisture sensor so there are no air pockets or rocks in contact with the sensor
  • Mark the location of the soil moisture sensor so you can find it in the future and avoid damaging it when aerating
  • Make all splices inside a valve box with a 3M™ DBR/Y-6 Direct Bury Splice Kit connectors
  • Refer to the following installation guides, which include additional instructions:

 

Brochures:

Product information about Baseline's patented Soil Moisture Sensors
This brochure describes how Baseline's irrigation products can benefit large sites such as schools and parks
Learn how to comply with California's Emergency Water Conservation Regulations and other water restrictions

Spec Docs:

Technical details, product detail and specification information for Baseline's original and compact soil moisture sensors
General specification information for Baseline's two-wire products in Microsoft Word format. Suitable for including in specifier's documentation.
General specification information for Baseline's two-wire products in Microsoft Word format. This non-proprietary spec does not give the manufacturer's name or the brand name of a product, which enables the irrigation designer to specify Baseline products while complying with the requirements in the bidding documents.

Support Docs:

A comprehensive look at how Baseline's soil moisture sensor works, and how to successfully start watering with soil moisture sensors
This document describes the LEED v3/2009 Water Efficiency credits and explains how irrigation specifiers can use Baseline products to achieve points in these credits.
Complete the extended warranty application and fax it to Baseline
Baseline Warranty Information
This document describes the LEED v4 Outdoor Water Use Reduction credits and explains how irrigation specifiers can use Baseline products to achieve points in these credits.

Case Studies:

Compares evapotranspiration-based watering with soil moisture sensor-based watering
The City of Eden Prairie, Minnesota installed Baseline controllers and soil moisture sensors. This case study demonstrates how much water and money they are saving.
The Portland Water Bureau conducted a two-year study to investigate the ability of soil moisture sensor-based irrigation to reduce water usage at landscape sites in Portland, Oregon.
The University of Florida compared the water savings on irrigation systems equipped with soil moisture sensors with other smart irrigation systems.
The Eastlake Vons shopping center in Chula Vista, California is reducing water consumption with a BaseStation 3200 irrigation controller
The City of Twin Falls Idaho manages more than 800 acres across 65 locations with their Baseline equipment
A look at how Red Diamond, Inc. in Moody, Alabama uses Baseline products to maintain their award-winning landscape
A look at how Bakersfield College uses Baseline products to save time and prevent overwatering at their athletic fields complex
A look at how Clif Bar Baking Company uses Baseline products to manage their facility in Twin Falls, Idaho
A look at how the City of Boise uses Baseline products to manage Esther Simplot Park in Boise, Idaho
A look at how Facebook uses Baseline products to manage the greenroof on their corporate campus in Menlo Park, California
A look at how landscape managers are using Baseline products to care for the grounds of the Edsel & Eleanor Ford House in Michigan
A look at how the Baseline irrigation controllers on Kiawah Island stand up to a hurricane
A look at how Baseline products are being used to manage the greenroof and planters at Levi's Stadium in Santa Clara, California
A look at how Nashville's Riverfront Park & Amphitheater uses Baseline products to manage their irrigation
A look at how San Luis Coastal Unified School District uses Baseline products to manage their school grounds
A look at how Sanger Unified School District uses Baseline products to manage their school grounds and athletic fields
A look at how landscape managers are using Baseline products to care for the grounds of the Travisso Master-Planned Community in Austin, Texas
A look at how The Woodlawn uses Baseline products to manage the irrigation of their green wall

Spec Drawings:

Detail on how to install a soil moisture sensor on a conventional wire system
Detail on how to install a Baseline soil moisture sensor in relation to a plant's root ball
Detail for installing soil moisture sensors on a two-wire system
Detail for locating a soil moisture sensor in a zone that is watered with part circle rotors
Placement of a soil moisture sensor in relation to a plant's root ball
Detail on how to install a Baseline soil moisture sensor with part circle rotors
Detail for installing soil moisture sensors on a two-wire system
Detail for installing a soil moisture sensor on a conventional wire system

Install Guides:

Installation instructions for the BL-5311 compact soil moisture sensor
Installation instructions for the BL-5315B original soil moisture sensor
Instructions for installing a BL-5200R powered biCoder. Includes instructions for connecting a biSensor.

Advanced Programming:

An overview of how you can use Baseline products to keep a pond or cistern full when it's being used for irrigation
Instructions for using a biSensor to monitor the water level in a pond or cistern. Describes how to program the BaseStation 3200 controller to refill the reservoir with a start condition
Instructions for using a biSensor to monitor the water level in a pond or cistern. Describes how to program the BaseStation 1000 controller to refill the reservoir with a start condition
Instructions for programming a BaseStation 3200 controller to pause irrigation programs while a reservoir refills to an acceptable level
An overview of using a pond or a cistern as a water source
Instructions for using a biSensor to monitor the water level in a pond or cistern. Describes how to program the BaseStation 3200 controller to shut down irrigation when the water in the reservoir drops below a certain level
Instructions for using a biSensor to monitor the water level in a pond or cistern. Describes how to program the BaseStation 1000 controller to shut down irrigation when the water in the reservoir drops below a certain level
Instructions for programming a BaseStation 3200 controller to shut down one water source when the water drops below a specified level
An overview of how Baseline's BaseStation 3200 irrigation controller deals with water restrictions
How to configure lower threshold moisture sensor-based watering on a BaseStation 1000 irrigation controller
How to configure upper threshold moisture sensor-based watering on a BaseStation 1000 irrigation controller
How to configure lower threshold moisture sensor-based watering on a BaseStation 3200 irrigation controller
How to configure upper threshold moisture sensor-based watering on a BaseStation 3200 irrigation controller
Tips that will help irrigators comply with water restrictions and avoid fines and penalties

Specification Tips for Soil Moisture Sensor Placement

A soil moisture sensor needs to be placed in the effective root zone of the plant it is monitoring. Usually the sensor will be making the irrigation decision for many plants or even multiple zones of plants with similar water needs, so it should be placed in the effective root zone of a representative plant.
 

Consider this analogy: if the thermostat in your home is next to a window or door that is left open on a hot day, the thermostat will sense the incoming hot air and cause the air conditioner to run continuously trying to lower the temperature. Similarly, if you put your soil moisture sensor in the driest spot of the landscape, your system will over irrigate the rest of the landscape in order to put enough water on the spot where the sensor is located.
 

Consider another example: if your thermostat is located above your oven, it will think the whole house is hot every time you cook, and it won’t allow the furnace to come on. Likewise, if you place your sensor next to your driveway, every time you wash your car, the sensor will think that the whole zone is wet and not allow irrigation in that area.
 

You will want to consider the following guidelines when deciding where to place your sensors:

  • Consider your various plant types first. For most sites, the ideal scenario would be to place one sensor in the lawn, one in the shrubs, and one in the trees if these plant types are in separate zones.
  • Consider how your zones can be grouped, and then bury the sensor in the zone that needs to be watered the most frequently (the one that dries out the quickest). This zone will be considered the “primary zone” for the scheduling groups in your irrigation controller.
  • Place the sensor in an average to slightly dry area (a spot that receives an average amount of water for that zone).
  • If you have very poor distribution uniformity (for example, mixed sprays and rotors), then you need to bury your sensor in a drier spot within the zone to avoid higher than average moisture readings. But keep in mind, the drier the area where the sensor is placed, the more the system will overwater the wet areas. 
  • Bury the sensor in the top third of the root zone, usually 2 - 3 inches deep.
  • Be sure to use some water to compact the soil against the sensor.
  • Mark or record the location of the sensor. This way, you can avoid damaging it when aerating or digging.
  • In your controller, create what is known as a scheduling group by grouping all zones that will water on the same interval together, such as lawn, shrubs, or trees. A scheduling group is made up of a primary zone (the zone the sensor is buried in) and linked zones (zones that water on the same interval as the primary).

 

Special Soil Moisture Sensor Applications

Sports Fields and High Use Areas

Baseline soil moisture sensors are commonly used for irrigating sports fields and other high use areas because of the system’s ability to separately manage the schedule on each field in the complex and to fill the profile up to the desired level on a stringent schedule.
 

When placing a soil moisture sensor in a sports field, the same rules apply as multiple sensors with one very important exception. Each field is usually its own scheduling group and will require its own sensor. This is because you may have a game on one field but not the one next to it. If this causes a difference in irrigation frequency, it will require a separate sensor to control the separate schedules.

The goals and challenges

  • Maintain a firm and consistent playing surface at game time (not so hard that it creates a higher risk of injury, not too soft or the surface will get damaged).
  • Schedule irrigation around games and other events.
  • Allow different schedules for different fields within the complex.
  • Deal with all the other challenges of a regular irrigation system, such as limited water supplies, distribution uniformity, maintenance needs, and so on...

Suggested features and practices

  • Use the upper threshold watering strategy. Set the upper threshold below field capacity to increase turf durability.
  • When possible, try to set the start time long enough before play begins to give the surface a chance to firm up. Start irrigating again after the event to help the field recover.
  • Place a sensor in each field that has a different schedule. The operator can pause the irrigation at any time and then the system will automatically “catch up” at the next opportunity.
  • Place the sensor in an average area in the field, but not in the highest use area. Avoid areas that may receive water from an alternate source such as water and drinks being poured out along the sidelines.
  • Keep the sensor wire below the aeration depth to avoid damaging it when aerating. Do not bury the sensor too deep, but keep the sensor itself within the most active part of the root zone. Mark the spot where the sensor is buried using GPS, a sight marker, or a measurement.

Engineered Environments (Greenroofs, Greenwalls, Interior Plantings, Containers)

Baseline's compact soil moisture sensors are ideal for use in engineered environments because these sensors are usually the only way to effectively automate the control of the irrigation system. The engineered environment presents many challenges that cannot be managed by an open looped system such as a weather-based system. The primary challenge is that an extremely small amount of plant available water can be stored in the soil reservoir. This is often coupled with extreme environments.

The goals and challenges

  • Often water conservation oriented sites
  • Shallow soils or low water holding capacity, often not enough holding capacity to last a full day during peak usage
  • Greatly increased evaporative effects over traditional on-grade plantings
  • High to very high replacement cost of plant material
  • Environmental benefits from keeping plants healthy and thriving

Suggested features and practices

  • Use lower threshold and set the turn-on point much closer to field capacity than would be necessary with on-grade plantings.
  • Use multiple start times per day to ensure the plants always have available water.
  • Set the threshold using an auto calibration method or by manually identifying the field capacity of the soil.
  • Set fairly short run times by visually monitoring the site for the first couple weeks. Run times need to be long enough to take the moisture from lower threshold to field capacity, but short enough to prevent runoff.

Steep Slopes

Baseline irrigation controls provide features to irrigate slopes as efficiently as possible. Using Intelligent Soak Cycles and the soil moisture sensor’s ability to measure only effective irrigation, you can minimize runoff and often eliminate it completely.

The goals and challenges

  • Eliminate or at least minimize runoff
  • Raise healthy plants
  • Avoid soil erosion or land movement caused from excessive irrigation

Suggested features and practices

  • Know your precipitation rate so you can work toward deep and infrequent watering as much as possible.
  • Put zones with steep slopes on a separate program.
  • Use Intelligent Soak Cycles™ and adjust cycle times by visually monitoring runoff during an irrigation event. It is not unusual to have cycle times as short as one or two minutes.
  • Bury the sensor in line with the slope so that water moving downhill will run past the sensor and not build up on the uphill side.
  • Not all slope issues can be remedied with controller settings. If you have one or more of the following issues, you may need to address the issue before adjusting the controller setting:
    • The slope is too steep.
    • The soil is heavily compacted.
    • The sprinkler heads put out water at too high of a rate (for example, VAN spray nozzles).
    • The zone has very poor distribution uniformity.

Subsurface Drip Tubing Irrigation

Subsurface irrigation systems can be difficult to manage because you cannot see the water being applied. The surface can be dry even when the root zone is saturated. A Baseline soil moisture sensor is the perfect tool for managing subsurface irrigation systems because the sensor is buried in the roots where the water is used.

The goals and challenges

  • Do not let the soil dry out. Very dry soil loses its capillary action and becomes difficult to rewet. In very dry clay soil, it is nearly impossible to move water up in the profile.
  • Do not over irrigate. Subsurface irrigation is often selected for its ability to conserve water. However, if you are not paying careful attention, water can easily be leached below the reach of the plant roots.
  • Know when the system is not functioning properly.

Suggested features and practices

  • Know your application rate. Don’t guess — use the manufacturer’s chart or run the calculations.
    • Irrigators often falsely assume that water is being applied very slowly and assign very long run times to subsurface zones.
    • Even when installed properly, some drip tubing can apply more than 1.4 inches per hour. This rate is likely higher than your soil can accept. 
    • To encourage the water to move up in the profile, set the application rate to match the infiltration rate.  
  • Use soak cycles to allow time for the water to move up through the soil to the roots.
    • Drip tubing manufacturers typically specify that you install the drip line 6 inches deep. However, this depth is often below the effective root zone of the plant, and consequently, below the recommended depth for burying the sensor.
    • If the drip line is 6 inches deep, bury the sensor in the effective root zone of the plant, and then use the lower threshold watering strategy.
  • Make sure the sensor is buried in the right spot. The same sensor placement recommendations apply as in other situations, but in practice finding the “right spot” is not as obvious.
    • Place the sensor in an area that receives average to slightly less than average water from the irrigation system. Typically, this location is between two emitters and half way between the drip tubes.
    • The sensor must be in the root zone of a representative plant.

Point Source Drip Irrigation

A properly installed and maintained point source system can be extremely water efficient because the amount of water each plant receives can be varied to suit the need. Using a soil moisture sensor to irrigate this type of system enables you to fine tune the amount (how much/how long to water), and then use the soil moisture sensor to adjust how often the system runs.

The goals and challenges

  • Adjust the frequency of irrigation to match changes in plant need and weather.
  • The number one challenge for a point source system is maintenance. The system needs to be checked periodically for the following issues:
    • Plugged emitters
    • Leaks
    • The emitters remain in the right spots to deliver the water to the plants
    • The size or number of emitters remains appropriate as plants grow

Suggested features and practices

  • Know your plant’s water requirement in comparison with the other plants in the zone.  Many point source emitters are labeled based on the GPH (gallons of water that is delivered per hour).Make sure the water is getting delivered to the entire root zone and not just on one side of the plant.
    • As a professional irrigator or landscaper, you need to use your knowledge of plants and water requirements for each plant in the zone.
  • Use soak cycles to allow time for the water to soak down to the sensor.
  • Use either the upper or lower threshold watering strategy.
  • Make sure the sensor is buried in the right spot. The same sensor placement recommendations apply as in other situations, but in practice finding the “right spot” is not as obvious.
    • Place the sensor in an area that receives average to slightly less than average water; usually not directly under the emitter and not too far away from it.
    • The sensor must be in the root zone of a representative plant – typically, the one that needs to be watered most frequently.

Water Feature/Cistern Keep Fill

You can use a Baseline soil moisture sensor to keep ponds and cisterns full. With no mechanical parts, they are much more reliable than standard floats, and much less expensive than most high quality float solutions.

The goals and challenges

  • Keep the water level constant

Suggested features and practices

  • Simple to use and install
  • Use any standard irrigation valve
    • Water usage can be measured
    • Will not affect the system’s ability to monitor and manage flow (with proper settings in the controller to account for the additional flow)
  • Use any standard valve biCoder (1, 2, 4 or Powered) to operate the valve
  • The fill rate needs to be slow enough to allow a full minute of operation each time the pond or cistern is filled. You might need to install an orifice and pressure regulator to slow the water fill rate.
  • Use the lower threshold strategy
    • Fill the pond or cistern to the desired low water mark, and then take a manual sensor reading.
    • Set the lower threshold to this number.
    • Set all 8 start times about 2 hours apart.
    • Set the run time of the zone at one minute or long enough to fill the pond or cistern to the desired level.
    • The water will now turn on for one minute up to 8 times per day depending on the need.

Heavy Clay

In heavy clay soil water infiltrates slowly, but clay soil holds more water per foot than other types of soil. For these reasons, irrigating in heavy clay can be challenging. If you set your soak cycles correctly and use a Baseline soil moisture sensor to closely monitor moisture levels, you can overcome those challenges.  

The goals and challenges

  • Get water down into the profile
  • Don’t drown plants
  • Don’t allow the soil to dry out

Suggested features and practices

  • Use soak cycles to slow the application rate to match the infiltration rate – know your math.
  • Standard sensor placement rules apply.
    • Even though the field capacity of heavy clay soils can be more than 4 inches of water per foot of soil, the plant available water in the same soil may only be 1.5 inches of per foot of soil.
    • If your plants have an effective root depth of 6 inches, they can only draw from half of that available water (approximately 0.75 inches).
    • Assume that you need to irrigate when your plants have used half of the moisture in the top 6 inches of soil. In this scenario, you will need to add .375 inches of water to restore the moisture to field capacity.
    • The infiltration rate of clay soil could be as low as 0.10 inches per hour (0.0017 inches per minute).
    • If the zone is watered by spray nozzles that put out 1.5 inches per hour (0.025 inches per minute) assuming the landscape is fairly flat and that the turf or mulch will help hold the water, it will take at least 14 minutes for 1 minute of applied water to soak in.
    • Given the scenario described above, you should set the zone to cycle for 1 minute and soak for 15, and set the total run time to 13-15 minutes. This setting assumes near perfect distribution uniformity, which you do not have with a spray head. Be sure to adjust your settings to compensate for your system’s distribution uniformity.
  • If you do not get the soak cycles set correctly, both the upper threshold and lower threshold watering strategies will result in over watering by watering longer or more frequently than needed.

Coarse Sand

Because water infiltrates rapidly in coarse sand, moisture often ends up below the effective root depth of plants.  A Baseline soil moisture sensor monitors the moisture level in the root zone and will cause the irrigation system to run multiple times per day in order to provide sufficient moisture for the plants.

The goals and challenges

  • Keep the soil from drying out
  • Manage dry spots

Suggested features and practices

  • Be prepared to water more than once per day.
    • Extremely coarse sand may only hold 0.5 inches of water per foot.
    • Even though plant roots can easily penetrate sand, a plant that is genetically programmed to have 4-6 inch roots will not have a 12-inch effective root depth no matter how good you are at irrigating.
    • If your soil holds 0.5 inches of water per foot and the plant’s effective root depth is 6 inches, the plant available water immediately following an irrigation cycle is only 0.25 inches.
    • Peak water usage for the plant may be as high as 0.41 inches per day depending on location; therefore, you might need to water more than once per day to keep the soil moisture level above the permanent wilting point.
    • Use the lower threshold watering strategy.
      • Set your threshold 1-2 points below field capacity.
      • Set multiple run times for each day trying to avoid the hottest time of the day.
      • Set run times based on application rates and desired watering depth.
        • For example, a spray zone applies 1.5 inches per hour, and the water holding capacity of the soil is 0.5 inches per foot. Filling the soil from dry would take 6 minutes. However, you are not going to start watering when the soil is completely dry, so you need to decrease the run time to something like 4-5 minutes depending on distribution uniformity of the zone.
  • Avoiding dry spots
    • Because coarse sand does not allow much horizontal movement of water, distribution uniformity issues are more noticeable in sand.
    • In order to avoid dry spots, you will have to water based on the lowest application rate within the zone.
    • The poorer your uniformity, the more water you will be wasting in the average and above average areas within the zone.