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Extension > Local Extension Offices > Dakota > County Agriculture Educator > Articles > Irrigation water management tools: Soil moisture monitoring

Irrigation water management tools: Soil moisture monitoring

Tensiometer for monitoring soil moisture

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What tools fit your management system?

Monitoring the amount of water stored in the soil can help irrigators decide when and how much to irrigate.

With recent advances in cellular telemetry and computer software, many new tools are available to monitor soil moisture and use that information to make irrigation water management decisions. Finding the right tools that meet your needs is all about finding the right equipment, and the right price, to optimize profitability.

This article will describe some of the traditional and newer options available for monitoring soil moisture.

As you read about the options available, consider the following questions:

  • What is your farm management style? Would you prefer a low-cost, hands-on approach, or a higher-priced, turn-key system?
  • How variable are your soils within a single field?
  • How much soil water holding capacity do you have to work with?
  • Products and brands shown below are only used as examples and are not an endorsement.

Traditional irrigation water management tools

Tensiometers:

Behave like a plant root and measure how hard it is for the root to extract water from the soil.

Strengths: Self-contained, accurate

Weaknesses: Requires some special equipment to setup and maintain, cannot be remotely read.

Costs: $150 per field or zone

Best fit: intensively managed or horticultural crops that requires routine infield management.

 

Resistance sensors:

Resistance based soil moisture sensors that are calibrated to provide the same readings as a tensiometers, but without the maintenance requirements.

Strengths: Accurate, requires no maintenance once installed, very versatile, can be read in many different ways.

Weaknesses: Requires special equipment to read.

Cost: $60 per field or zone

Best fit: Growers that are looking for low cost ways to precisely apply irrigation water across diverse soil types.

 

Capacitance Sensors:

Soil moisture sensors that provide  volumetric water content (when properly calibrated).

Strengths: Provides volumetric soil water content that can be used in conjunction with irrigation scheduling to forecast days until next irrigation.

Weaknesses: Expense, may require  dataloggers/telemetry, and needs to be well calibrated to soil type to get accurate reading.

Cost: $200-$3000 per field or zone

Best fit: Growers that have very uniform soil types and, or are looking for a integrated solution with lots of technical support.

 

Irrigation Scheduling Software:

In Minnesota and North Dakota this is an Excel based program that allows growers to schedule irrigation applications based off of a soil water balance.

Strengths: Can monitor multiple fields quickly and accurately, integrates record keeping, and requires no special equipment.

Weaknesses: Steep learning curve and daily entry of accurate climate data.

Cost: $0
 

Enhanced, real time irrigation water management tools

Cellular telemetry for soil moisture sensors

The ability to remotely monitor soil moisture conditions, using the previously mentioned sensors, in farm fields has been around for the last decade, but recent declines in costs and newer application platforms have made this a much more powerful management tool for irrigators.

These self-contained cellular devices also offer more than just soil moisture monitoring. They can provide real-time, site-specific precipitation data, start and stop irrigation, or even change the amount of irrigation water being applied from across town, or from across the state. Many irrigation companies offer remote management capabilities on their newer pivots, but there are also companies that offer retrofit options for many older model pivots for less than $2000.

Joshua Stamper, University of Minnesota Extension Irrigation Specialist

Posted 3-30-2016

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