Salinity of irrigation water
Salinity of irrigation water. This is what we will learn about today
Agricultural crops need sufficient quantity and good quality of irrigation water to help them grow and reach economic production.
The United Arab Emirates is considered one of the countries that are located within the arid and semi-arid regions and suffers from a scarcity of water resources, as it relies mainly on groundwater to irrigate agricultural crops.
The factors of high evaporation rates, lack of annual rainfall, and depletion of groundwater reserves through overpumping have led to a noticeable decrease in groundwater levels and a deterioration in its quality.
Identifying the characteristics of the water used to irrigate crops is necessary and important and cannot be overlooked in relation to its relationship to plant growth, as well as its impact on the characteristics of agricultural soil.
Why care about the salinity of irrigation water?
for many reasons :
- The salinity of irrigation water affects soil fertility, as dissolved salts accumulate on the soil surface and in the root zone, depending on the type of soil.
- The effect of irrigation water salinity on crop productivity, as agricultural crops differ in their sensitivity to dissolved salts in irrigation water.
What are the sources of salinity?
Among the most important sources are the following:
- Salts present in the soil resulting from the continuous dissolution and erosion of rocks (the mother soil).
- The high ground water level resulting from the absence of good drainage after irrigation.
- The high ground water level resulting from the absence of good drainage after irrigation.
- Dissolved salts added through irrigation and fertilization water.
What are the factors determining the suitability of irrigation water for agriculture?
The most important factors are the following:
- The amount of dissolved salts and their concentrations, where most of the dissolved salts move
With irrigation water, it seeps into the bottom of the soil or remains on the surface of the soil, causing danger to the plant in terms of growth and production. - Percentage of concentrations of harmful elements in irrigation water, the most important of which are sodium, chloride, and boron.
The following is the effect of these harmful elements on the plant
Sodium:
- Sensitive plants are affected and burn and appear on the leaves when the sodium level reaches between
- 0.25% 0.50% (based on weight).
- Trees are affected when the sodium content reaches between 0.25% – 0.50% (based on weight).
Chloride:
- This element moves easily with the soil solution and is consumed by the plant through transpiration
- Chloride collects in the leaves.
- Most fruit trees tolerate concentrations ranging between 6-10 (mg/L), however
- Damage appears on the leaves at concentrations ranging between 0.6-1.0%.
Boron:
- The concentration reaches about 15 (mg/L) in high salinity water.
- The upper limit of the permissible boron concentration for plant growth ranges between 2-4 (mg/L).
Measuring the salinity of irrigation water:
- Periodic samples of irrigation water are taken and analyzed in the laboratory to measure the amount of dissolved salts
In water, it is expressed in ppm or mg/L
(Meaning a milligram of dissolved salts in one liter of water) - Suppose that the salinity of irrigation water after analysis in the laboratory indicates 10,000 ppm
This means that 1% of the weight of water comes from dissolved salts in irrigation water. - If dissolved salts are detected in the soil, soil samples are also taken and analyzed in the laboratory
Modern techniques have now been introduced to monitor salt movements in the soil sector
By placing monitoring devices in the field that help detect changes in salt concentrations in the soil
This is done by transferring the data/data to the data analysis center or laboratory.
The effect of irrigation water salinity on crop production
Agricultural crops, including vegetables and fruits, are affected by the amounts of dissolved salts in irrigation water. An increase in the concentrations of dissolved salts, especially harmful ones, leads to a loss in production. The attached table shows the percentage of this loss when using irrigation water with different salinities and the extent of its tolerance to dissolved salts.
| Crops | Percentage of loss in production | Relative tolerance to salinity | ||||
| zero | 10% | 25% | ||||
| Irrigation water salinity (decisiemens/m) (ds/m) | ||||||
| Fruit crops | ||||||
| Palm | 2.7 | 4.5 | 7.3 | durable | ||
| apples | 0 | 1.5 | 0 | sensitive | ||
| an orange | 1.1 | 1.6 | 2.2 | Medium endurance | ||
| grapefruit | 1.2 | 1.6 | 2.2 | Average tolerance | ||
| Lemon | 1.0 | 1.5 | 2.3 | Average tolerance | ||
| grapes | 1.0 | 1.7 | 2.7 | Average tolerance | ||
| apricot | 1.1 | 1.3 | 1.8 | sensitive | ||
| Vegetable crops | ||||||
| beans | 0.7 | 1.0 | 1.5 | sensitive | ||
| radish | 0.8 | 1.3 | 2.1 | Average tolerance | ||
| tomatoes | 1.7 | 2.3 | 3.4 | Average tolerance | ||
| carrot | 0.7 | 1.1 | 1.9 | sensitive | ||
| lettuce | 0.9 | 1.4 | 2.1 | Average tolerance | ||
| Potato | 1.1 | 1.7 | 2.5 | Average tolerance | ||
| onion | 0.8 | 1.2 | 1.8 | sensitive | ||
| spinach | 1.3 | 2.2 | 3.5 | Average tolerance | ||
| Table beets | 2.7 | 3.4 | 4.5 | Average tolerance | ||
| pepper | 1.0 | 1.5 | 2.2 | Average tolerance | ||
| cabbage | 1.2 | 1.9 | 2.9 | Average tolerance | ||
| option | 1.7 | 2.2 | 2.9 | Average tolerance | ||
| Field crops | ||||||
| Barley (Gulf) | 4.0 | 4.9 | 6.3 | durable | ||
| Sorghum | 4.5 | 5.0 | 5.6 | durable | ||
| Levantine corn | 1.1 | 1.7 | 2.5 | Average tolerance | ||
| Clover | 1.3 | 2.2 | 3.6 | Average tolerance | ||
| Rhodes fodder | 2.7 | 6.35 | durable | |||
How to classify it according to its salinity?
It is divided as follows:
Fresh: Its salinity is less than 1000 ppm
Low salinity: 1000 – 3000 ppm
Medium salinity: 3000 – 10000ppm
Highly salty: 10,000- 35,000 ppm
Sea/ocean: Its salinity is more than 35,000 parts per million
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