Avoiding salinization in soils thanks to an irrigation system

The quality of an irrigation water is not only explained by the specific conditions of its use, but also by external factors such as crop, climate, soil, irrigation method and management, etc.

Water quality is largely explained by the salinity of the water. This quality can be explained by different causes, although some of them are generated by anthropocentric causes such as the accumulation of salts due to over-irrigation, but also by a bad use of fertilizers in cultivation or by improper use of animal waste substances, or by the use of reclaimed water.

However, one of the main causes of salinization of both water and soil is caused by the strong evaporation that occurs in desertified or desertifying latitudes, which is avoided with the DeepDrop® irrigation system since the water is carried directly to the roots. We will see that this has another advantage.

All of this also affects soils and can have serious consequences on crops, since it affects their yields and can even make soils unsuitable for agriculture.

Salinity

Salinity is defined as the concentration of dissolved mineral salts, present in water or soil, referred to a unit of volume or weight. All irrigation waters contain dissolved salts, the type and quantity of which depend on their origin and the course they have followed before use.

Salinization affects plants and trees when the concentration of soluble salts in the water exceeds the concentration required for good plant growth.

Consequences of salinity

The consequences of salinity on crops are varied and represent an international problem since it affects the decrease in soil fertility, the inability to grow and harvest plants, problems in absorbing nutrients, destabilizing the nutrition of soils, plants and trees. In addition, it reduces crop productivity due to ion toxicity, generates variations in acidity levels, accumulation of salts that generate more problems in crops such as chlorine, sodium and boron in different parts of the plants (seeds, stems and leaves). And finally, the decrease in water potential.

The salts that generate the most toxicity in crops

The toxicity of each of the salts varies according to the crop, as well as the symptoms they produce in plants. The salts that most often damage crops are excess sodium, chloride and boron.

An excess of sodium causes dryness or burning on the outer edges of the leaves. If the problem persists, dryness follows along the nerves to the center of the leaf. Citrus, avocado and beans are the most sensitive crops to excess sodium in the soil, while wheat, cotton, barley, alfalfa and sugar beets, for example, are very tolerant.

Chloride that accumulates in leaves up to a certain level of leaf weight can have very detrimental effects. These are seen as burns at the tip of the leaves and move towards the edges. It affects mainly woody crops, with stone fruit trees, citrus, avocado and grapevines being very sensitive.

Boron, unlike the previous ones, affects both woody plants and annuals. Even in low concentrations it seriously damages some plants, but it is an essential element for good crop development. Its effects are usually seen by a yellowing of the tips of the oldest leaves that moves to the center of the leaves between the nerves and in some other areas of the plant. The plants most sensitive to excess boron are, among others, beans, stone and pome fruit trees, grapevine and avocado as well as sunflower, wheat, corn and cotton.

Irrigation and salinization methods

Depending on the irrigation method used, the accumulation and distribution of salts will greatly change soil quality as well as crop production. In turn, choosing the right irrigation method allows for more precise control of the concentration of salts in the soil.

Furrow irrigation:

Salinity tends to increase in certain areas, depending on the shape of the furrows, which may allow plants to escape from high salt concentrations. However, water consumption is very high, which is not convenient in countries at risk of desertification.

Flood irrigation:

In well leveled surfaces, it allows the application of water of lower quality than in other methods, since salinity control is easier. But as in furrow irrigation, water consumption is very high and this is a very important parameter in arid and semi-arid areas.

Sprinkler irrigation:

It offers the possibility of applying lower quantities of water than those needed in surface irrigation. But the main risk of applying saline water with sprinkler irrigation is that the salts come into contact with the leaf surface and when absorbed cause burns to the leaves of plants and trees. This in turn means that sprinkler irrigation requires higher quality water than surface irrigation.

Drip irrigation:

Drip irrigation avoids leaf damage and decreases water consumption by keeping soil moisture high, which allows keeping salt concentration low due to the frequency of applications. It is especially beneficial in sandy soils that have a low water holding capacity and where the variation in water content during the irrigation interval is more pronounced than in coarser textured soils. The only drawback is the need to remove salts that accumulate at the front of the bulb.

Drip irrigation with DeepDrop®.

The DeepDrop® drip irrigation system has the advantage of drip irrigation explained above, in addition to the dissolution of salts in the tube that carries the water to the subsoil to conduct it to the root system of plants and trees. In addition, being a subway irrigation system, compared to surface drip irrigation, it avoids any salinization of the surface since no water is lost above it and, in turn, salinization caused by evaporation of water that has not filtered into the soil is avoided.

Application of DeepDrop® according to water type

The DeepDrop® irrigation system advises the use of these flow rates depending on the type of plant or tree, type of soil and type of water available:

2 L/H dripper: black base

Horticultural crops, ornamentals, shrubs, trees with clay soils. For all types of soils, and for clay soils only the flow rate of 2 L/H is recommended. Soft water.

4 l/H dropper: green base

Arboreal. Loamy soils. Moderately hard water. Watering times are reduced compared to 2L/H devices.

8 l/H dripper: blue base

Arboreal. Sandy soils with water absorption capacity. Hard water. Very short watering times.