Preparing your soil for Electrical Conductivity 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 electrical conductivity.
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.
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.
Electrical conductivity testing and saline mitigation
Electrical conductivity and salinity are closely linked.
Certain salts, like sodium, also contribute to conductivity but can be detrimental for crop development if they reach excessive levels.
Victor Beya Marshall, Ag. Eng. M.Sc., based in Santiago, Chile, shares his findings here on saline mitigation.
"In one of my research papers, I explored saline mitigation through the use of biostimulants, specifically Ascophyllum Nodosum Extract applied via drip irrigation.
We discovered that this management technique improved soil health by increasing organic matter, enhancing microbiology, stabilizing soil, boosting water retention and porosity.
Additionally, it reduced soil compaction, which in turn improved salt displacement.
In this context LAQUAtwin ion sensors could be valuable for comparing different management practices.
They can be used to monitor electrical conductivity and track nutrient dynamics throughout the season, helping to understand how these amendments impact soil chemical dynamics and enabling more informed decision making".
Understanding Conductivity Units and Overview of Typical Conductivity Values
We will be using pocket conductivity meters LAQUAtwin EC-11 to demonstrate electrical conductivity values and conversion.
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.
How Should I Test EC in Soil?
There are four common ways of preparing your soil sample to test for 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 the side-by-side comparison table below:
How to Collect Soil Samples?
For the most accurate soil test, it is 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
Soil Sampling Protocol
How to Measure Electrical Conductivity of Soil Solution
By now you have prepared your soil solution with the help of lysimeter, soil slurry (Dilution 1:2), or a Saturated Media Extract method.
1) Calibrate your conductivity meter to ensure high precision. Daily calibration is considered to be the best practice.
2) Place soil solution onto the sensor of the meter (HORIBA LAQUAtwin EC-11 Conductivity meter).
3) Wait for the meter to display stable reading before recording the results.
4) We recommend taking 3 measurements of the same sample and taking the average result for best accuracy.
5) After the measurement rinse the electrode under the running water.
Now you have your sample reading, you can refer to the reference values below.
Remember though that these values are inconclusive, and it is always better to check for salinity and macronutrients separately.
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.
Unless you're working with hydroponic crops, maximizing yield often requires specific macronutrients testing.
If you are a grower who wants to implement comprehensive nutrient monitoring for your crop, or simply start testing soil and plant sap yourself rather than relying on laboratories, check out our user-friendly field equipment NutriCheck LAQUAtwin.
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For any queries about EC or nutrient testing procedures, feel free to reach out via our 'contacts us' page.
-Seb from TestAgro
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