Measuring Salinity in your Land
Test your water and its conductivity
Water salinity refers to the concentration of dissolved salts in water. While plants require a specific amount of salts for healthy growth, excessive salinity can become detrimental, leading to very harmful effects.
Measuring the salinity of water is then very important, especially if you're using water from a borehole in a coastal area, as it can affect your plants. Over certain thresholds, you will need to grow plants that are adapted to higher salinity levels and use special techniques to mitigate the effect of salinity on plants.
To measure how salty your water is, you can use a simple device called an Electrical Conductivity Meter, or EC Meter. This tool is affordable (it usually costs between 14 to 50 EUR) and reliable. You can easily find it online by searching for "buy EC Meter."
To explain a bit more in detail, the EC Meter measures something called the electrical conductivity (EC), which is a way to check how well the water can carry electricity. It is most of the time closely related to the salinity level of the water. The more dissolved salts and other substances there are in the water, the better it can carry electricity, and the higher the EC reading will be. The results are usually shown in microsiemens per centimeter (µS/cm) or decisiemens per meter (dS/m).
How to use the EC Meter
For Water: Simply fill a glass with water from your borehole or irrigation source, and dip the EC Meter into it.
For Soil: Mix some soil with an equal amount of water* in a container, stir it, let it sit for 15 minutes, and then measure the water with the EC Meter.
* To accurately test soil conductivity using an EC meter, you should use distilled or deionized water for mixing with the soil. These types of water have very low or negligible conductivity, which ensures that any conductivity measured after mixing the soil and water comes from the dissolved salts in the soil, not impurities in the water itself. Avoid using tap water or bottled water, as they may contain minerals or other impurities that could affect the accuracy of your test results.
In the table below, you will find the classification of the FAO about the irrigation water salinity and then can compare with yours.
| Water class | Electrical conductivity (μS/cm) | Electrical conductivity (dS/m) | Type of water |
|---|---|---|---|
| Non-saline | <700 | <0.7 | Drinking and irrigation water |
| Slightly saline | 700-2,000 | 0.7-2 | Irrigation water |
| Moderately saline | 2,000-10,000 | 2-10 | Primary drainage water and groundwater |
| Highly saline | 10,000-25,000 | 10-25 | Secondary drainage and groundwater |
And here, the soil’s EC information from FAO:
| Tolerance of crops | Soil EC |
|---|---|
| Sensitive | 0-2,000 μS/cm |
| Moderately sensitive | 2,000-3,000 μS/cm |
| Moderately tolerant | 3,000-6,000 μS/cm |
| Tolerant | 6,000-10,000 μS/cm |
Also, do not forget that the EC is closely related to salinity but not 100% related. It is important to get a full water analysis done from time to time to know the exact amount of different components of the water. Not only will it give you a more accurate result about salinity but it will also show if you are facing any other water issues. It is more costly but worth it.
Here is an example of a water analysis of a Tavira inhabitant:
How to understand the analysis?
The conductivity here is 1,820 µS/cm, indicating slightly saline water. Since most salt-sensitive crops require water with conductivity below 1,000 µS/cm, they should not be included in future plans for this person. Additionally, it’s important to consider saline irrigation mitigation techniques to manage this water’s quality and prevent the negative impacts of salt on crops.
Two important components of salt are sodium (Na⁺) and chloride (Cl⁻), which make up most of the salt in seawater. Monitoring these can help you better understand your water’s salinity. Here are the different thresholds:
| Na+ concentration (mg/l) | Comment |
|---|---|
| <70 | Low, safe |
| 70-200 | Medium, may affect sensitive crops |
| >200 | High, likely to cause problems |
| Cl- concentration (mg/l) | Comment |
|---|---|
| <70 | Very good |
| 70-140 | Good |
| 140-350 | Medium, may affect sensitive crops |
| >350 | High, likely to cause toxicity issues |
We see that in our example, the salinity levels are very high and need to be addressed immediately as part of the garden management plan.
Finally, keep an eye on the Sodium Absorption Ratio (SAR). This measures how much sodium is in the water compared to calcium and magnesium. If there’s too much sodium, it can cause problems with the soil, making it harder for water to soak in and plants to grow well.
| SAR values | Comment |
|---|---|
| 0-3 | Very good |
| 3-9 | Good to moderate |
| 9-12 | Fair to poor, significant risk of damage, suitable only for well-drained soils |
| <12 | Very poor, unsuitable for growing |
Taking this table’s reference values into account, in our earlier example the SAR level is still good.
After having done an assessment on the situation regarding your soil and water salinity, it’s now time to have a look at some of the available solutions, in case your land is indeed being affected by damaging salt levels.
Keep scrolling to find more content in this Research series.
This article was compiled by Miguel COTTON & Angela DUZAN. If you have any questions or suggestions, do not hesitate to contact us. Please write us anytime at miguel@orchardofflavours.com
Interested in more content relating to the growing issue of soil salinity and its effects on plants and soils, as well as solutions? This article is part of our Research series "Salinity and Edible Plants":
