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How to Measure Electrical Conductivity (EC) in Soil

Updated: May 30


Preparing your soil for EC measurement follows similar principles to soil prep for pH measurement.

Typically, EC soil analysis requires a more time-consuming procedure than a straightforward liquid analysis. Use our simple guide below to choose the soil sampling and testing method that suits your needs best.


Here we will cover:



Electrical conductivity (EC) as an indicator of soil health


Soil electrical conductivity (EC) measures the soil's water capacity to conduct electrical current which is directly linked to the concentration of dissolved salts and ions (nutrients) in the soil.


This conductivity is used as a general soil quality and fertility indicator.

It is an important indicator of soil health since it impacts crop yields, nutrient availability, and the activity of soil microorganisms.


Soil conductivity is influenced by various factors, such as the soil mineral composition, ground water characteristics, and irrigation methods.


Irrigation can either reduce salt levels in the soil through leaching or accumulate salts from fertilizers, affecting the overall conductivity of the soil.


 

How does electrical conductivity impact growth and development of my crop?

Electrical conductivity does not directly influence plant growth; however, different crops have varying tolerance levels for EC.


High EC values can hinder the activity of soil microorganisms, affecting vital soil processes such as respiration, decomposition, and nitrification.


EC serves as an indirect indicator of nutrient availability, as its value correlates with the concentration of nutrients in the soil.

The conductivity measurement provides insight into the presence of salts and nutrients in the soil or soil solution; generally higher levels of these elements lead to increased conductivity.


Important to note: even if your conductivity value is within the expected range, deficiencies in specific nutrients may exist.

While conductivity results can correlate with crop development, unless you perform soil testing for other essential parameters, like pH or key macronutrients (NPK and Calcium), you will not get a comprehensive overview of your crop developmental status.

Certain salts, like sodium, also contribute to conductivity but can be detrimental if they reach toxic levels.


This highlights the importance of elemental nutrient analysis - like performing plant sap testing or analyzing the soil for nutrients - it gives you a clearer idea of how healthy your crop is and what nutrients it needs.

Sample extract from our NutriCheck Guide: Ideal EC data ranges based on different crop types

Do you want to know the optimal soil conductivity level for your type of crop? Our NutriCheck guide (comes with TestAgro NutriCheck or NutriCheck Max kits) covers 1000+ data points ranging from EC references for 50+ crops to optimal reference tables for nutrients like Nitrate, Phosphorus, Calcium and Potassium.
 

Understanding Conductivity Units and Converting Meter Results

Usually, the conductivity is measured in Siemens (S) and is expressed like this:


​ - milliSiemens per centimeter = mS/cm (usual unit displayed on field testers)

- microSiemens per centimeter = µS/cm

- deciSiemens per meter = dS/m


Conversion:

​ - 1 mS/cm = 1,000 µS/cm

- 1 dS/m = 1 mS/cm

NB: HORIBA LAQUAtwin conductivity meters have an auto-ranging function, which means that results are expressed in µS/cm from 1 to 2000 µS/cm.

If the data point exceeds this range, the meter will automatically switch to mS/cm.

Overview of typical conductivity values

 

How Should I Test EC in Soil?

As with soil testing for pH, there are four common ways of testing Soil Conductivity:

3. Saturated Media Extract (SME): saturates soil sample with water, based on moisture levels.

4. Direct measurement (details below)


To decide which method is best for you, refer to side-by-side comparison table below:


 

How to Collect Soil Samples?

For the most accurate soil test, it's crucial to gather representative soil samples from the field you wish to analyze. As soil composition varies significantly, we recommend collecting diverse soil samples randomly across the field to ensure a homogeneous representation.

Best Practices:


- Ensure all soil samples are collected on the same day.

- Maintain sampling consistency: always collect samples at the same depth and distance from the plant.

- Collect a minimum of 10 samples per acre from randomly selected spots.

- Collect samples at the level of the crop roots.

- Use a composite sample: once all samples are collected, mix them to create one sample


​Discover our Sampling Expert kit that includes all the equipment so you can prepare samples right in the field.


Soil Sampling Protocol

1. Use a soil sampling probe to collect samples at a depth of 6 inches (note: root depth varies with crop type, so verify the specific depth for your crop).

2. Collect approximately 1 ounce (around 30g) for each sample.

3. Put all samples into a plastic bag.

4. After collecting all soil samples, mix the soil inside the plastic bag to create a composite sample.


 

How to Measure Electrical Conductivity of Soil Solution

- Prepare a soil solution choosing your preferred sampling method: soil slurry (dilution 1:2), Saturated Media Extract method or SSAT (using a lysimeter tube)

- Before you measure your soil solution, make sure to calibrate your conductivity meter to ensure high precision - daily calibration is considered the best practice.

- Place the solution onto the sensor of the meter (HORIBA LAQUAtwin models) or place the solution in a beaker to immerse the EC sensor in the solution for Hanna EC meter.

- Wait for the meter to display stable reading before recording the results.

- We recommend taking 3 measurements of the same sample and taking the average result for best accuracy.

- After the measurement rinse the electrode under the running water

Direct Measurement of Soil EC


Hanna HI98331 Soil Conductivity Tester is designed for Direct soil EC testing.

It allows you to skip the soil sampling and preparation steps, as the Conductivity is tested right in the soil.

- Calibrate the EC probe prior to measurement.

- Insert the electrode insert into the hole.

- Wait for stabilization of the reading

- After measurement, gently wash off leftover soil (avoid using a cloth).

Note:

- Direct soil EC testing is not recommended if the ground is stony or hardened as the electrode can be damaged. In this case the SSAT or ½ soil preparation method is recommended.

- Take various measurements to get a representative overview of the entire field.



Interpreting EC Results and Actionable Insights

Testing conductivity levels helps determine available water and water-soluble nutrients for plant uptake.


While EC offers ample information for amateur and hydroponic growers, professional growers and agronomists often delve deeper, analyzing nutrients for a more comprehensive understanding of plant nutritional needs.

In summary, unless you're working with hydroponic crops, maximizing yield often requires specific macronutrients testing.

Fortunately, there are plenty of resources on this topic and we'll cover it in our posts.

Stay updated by subscribing to our newsletter for new articles, grower tips, and original research.

For any queries about EC or nutrient testing procedures, feel free to reach out via our 'contacts us' page.

-Seb



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