Agricultural irrigation water-Parameters to take into account-Accumulation of salts- (II)

The quality of agricultural irrigation water, the parameters to be taken into account and the pH influence the quality of the crops and the land.

Agricultural irrigation water

The best thing for the plants is that they have rainwater, if it is fine and that it meets their needs. It would also wash their leaves and benefit their breathing.

But this does not always happen and less in the central and southern areas of the Peninsula.

The farmer is forced to compensate for the lack of rainwater with irrigation and one of the problems he has to solve is whether the water available is the most adequate.

Pure water has no salts, therefore it does not conduct electricity. Its components are oxygen and hydrogen in the proportion H 2 O. It is for this reason that to assess whether the water has salts, let's look at how it conducts electricity.

Agricultural irrigation water is the main cause of the contribution of salts to the land in addition to fertilizers.

Parameters to take into account in agricultural irrigation water

We are going to develop in detail the parameters to take into account in agricultural irrigation water:


It is the amount of salts in the water. The most common salt is sodium chloride (NaCl)

We say that the water is fresh in rivers and lakes because the sodium chloride content is low

Salinity varies with the degree of evaporation. The water that evaporates does not contain salts and these accumulate in the ground.

  • Salinity is measured with electrical conductivity in dS / m, ( deciSiemens per meter) which is the capacity of the water to conduct electricity by meter.
  • Comparing the results of the conductivity of the irrigation water with rainwater, which has a conductivity of 0.15 dS / m , is the way to see if it has a high salt content or not.
  • In irrigation water, it is normal for salinity to be between 0.8 and 2.6. In seawater the salinity ranges between 30 and 60dS / m.
  • El exceso de sales induce en la planta un desequilibrio iónico y estrés con la correspondiente falta de agua. La salinidad repercute directamente en:
    • La germinación.
    • El crecimiento.
    • Altera la transpiración porque disminuye el crecimiento de las hojas.
    • Se reducen los estomas de las hojas.
    • Se retrasa la floración.


It is the amount of concentrated sodium with respect to calcium and magnesium and that we must analyze in the laboratory. It is measured in RAS or sodium absorption ratio by the soil .

Sodium tends to disperse the soil, especially clay particles. This causes the pores to become blocked and there is a greater risk of waterlogging. The soil becomes compact and lacks aeration, the plant has difficulties to absorb water and nutrients.

Sodium salts increase the pH.

The pH or acidity or alkalinity problem

The pH is the measure of acidity or alkalinity that indicates the amount of hydrogen ions present in the water .

pH acido o alcalino en el agua de riego agrícola
Measurement of pH-Low or Acid-Normal for irrigation-High
Agua de riego agrícola-pH del agua-acidez y alcalinidad
Color scheme to see the accumulation of water- Acid and alkaline medium in the pH of irrigation water

Importance of pH in agricultural irrigation water

The pH of the water directly affects the crop.

  • high pH : influences the absorption of nutrients because they become insoluble and are not easily absorbed. The plant suffers from a lack of nutrients and the soil accumulates excess salts.

The accumulation will be greater as the agricultural irrigation water is more acidic.

  • A low pH : seriously damages the roots and therefore the absorption of the plant. High acid soils can make the plant toxic by accumulating aluminum.

How to lower the pH:

We can add nitric acid, phosphoric acid or sulfuric acid which acts much more slowly on the absorption of the plant. If the pH is acidic and we do not raise it, the plants are deficient in potassium and later in nitrogen.

To raise the pH:

Caustic soda or caustic potash is used. We must raise it with control, slightly acidic is better than more alkaline. If the pH is very alkaline, the plants have iron and zinc problems and long-term phosphorus problems.

The pH can be easily measured with strips of litmus paper. It is enough to compare it with the color sample to assess the acidity or alkalinity.

Problem of the accumulation of salts in the ground

When a plantation is irrigated, even though it is perfect water, salts accumulate and there is a tendency to produce salinity in the land by accumulation, as we see in the following diagram.

Types of water
Types of accumulated water-salts and wet bulb. Sensors / probes at two depths. 1-2-Radicular System. 3-Wet bulb. 4-Medium salinity zone. 5-High salinity. 6-Soil filtration 7-Perspiration. 8-Evaporation. 9-Drip irrigation.

We have already dedicated an article to the problem of salinity in intensive and superintensive crops .

If we add low-quality water to the already traditional problems due to continuous irrigation, the problem increases and the crops suffer alterations.

In times of heat, evaporation is greater and irrigation is also greater, the accumulation of salts increases.

If salinity is not controlled, the land is less and less productive. We must have a balance between the contribution of salts and those that the crop needs so that the soil does not accumulate them.

The accumulated salinity is sometimes proportional to the irrigation management. We must have a rigorous control of both the quality of the water and the quantity, which is what the crop needs.

Subsoil conductivity and humidity in the land can be measured with sensors Plantae , in real time and observe it on your mobile or tablet.

Tipos de agua para riego
1-Sensors at two depths. 2-drip irrigation with two pipes. 3- Flowmeter. 4- Almond trees with agricultural irrigation water and salinity controlled by sensors / probes and humidity, temperature and conductivity for soil.

Plantae sensors help you control humidity from the soil, the accumulation of salts in crops ,




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