Salinity in intensive and superintensive plantations is one of the problems encountered by the farmer. We will try to explain it and how to avoid it.
The control of salts in a field is known as " edaphic study ". Edaphology is a branch of science that studies the composition and nature of the soil in its relationship with plants and the environment that surrounds them.
What is the salinity of agricultural soil?
Salinity in soils is contamination by soluble salts . Salinization is measured by the concentration of salts in a certain area.
The most common salts are:
- Chlorine, sulfate, nitrate and bicarbonate ions.
- Cationes de sodio, calcio, potasio y magnesio.
The excess of these salts reduces the development of plants in general and can even make the land unproductive. The saline stress that occurs influences:
- Photosynthesis influencing its growth.
- In its germination and in its shoots.
It is a serious problem for agriculture and is intensified in intensive crops due to increased irrigation if it is not controlled.
To calculate the amount of salts we measure:
- Electrical Conductivity (CE).
- Also the Percentage of Exchangeable Sodium (PSI).
- The Sodium Absorption Reaction (RAS).
Conductivity increases with the amount of salts.
As the angle is greater, its slope increases, which we can easily calculate with the calculator with the «tan» key. If the slope is greater than one, the crop begins to lose productivity.
With salinity the soil compacts and the ability to absorb water by the root system decreases.
Salinity does not affect all crops equally and they are usually classified into:
- Moderately sensitive.
- Moderately tolerant.
How is salinity produced in intensive and super-intensive plantations?
- It may be due to the presence of saline rocks, but it is usually due to the type of water used, especially in coastal areas, that seawater seeps into the aquifers. Therefore, the first thing that interests us is an analysis of the irrigation water. The less you have the better.
- It can also be due to poor irrigation management in intensive and superintensive productions of olive trees and others crops and improper use of fertilizers.
Irrigation in areas of extreme heat is not absorbed 100% by the plant, the heat causes part of the irrigation water to evaporate and the salts remain in the plant environment because the salts do not evaporate.
This problem is exacerbated if the risks are abundant and spaced apart in time. In turn, the plant can suffer water stress due to lack of water in the period that it is not watered. When it is irrigated, it is not able to absorb the salts that accumulate between one and the other.
At this point the composition of the soil also intervenes. A study of the terrain is necessary to combine the distance between the risks and the amounts that we must contribute. The more clayey, the more problem.
Excess agricultural salinity and where it accumulates
- First we see with the scheme how irrigation forms the wet bulb and in the superficial part the water evaporates the larger the area and the more heat there is. The width of the wet bulb depends on the type of terrain. As it is more clayey it is wider and therefore gives rise to more evaporation.
- Secondly, we analyze how salts accumulate when the irrigations are very abundant and far apart. Evaporation causes salts to accumulate in the wet bulb and around the roots of the plant.
- Third, and once we observe the problem, one of the solutions is to wash the area, but this causes the salts to move from the wet bulb, but not to disappear. If the soil is also clayey, the accumulation will make a plate of salts that ends up being very harmful for the plantation and in the long run for the land. The more gritty, the more the salts are filtered out with the washings.
- Finally, it is recommended that in case of rain, drip irrigation should be maintained to prevent surface salts from going to the root zone. It is a way to have the bulb isolated from excessive salts.
Classification of soils affected by salts
Effects of salinity in agriculture
- The main one is the sealing of the soil pores, preventing the nutrients from moving.
- The floods that negatively affect most of the crops as we already indicated in other articles.
- Root suffocation prevents root growth and normal elongation that can lead to serious plant problems.
- Stomatal closure, a serious problem that leads to altered perspiration and carbon dioxide concentration.
Solutions to salinity in intensive and superintensive plantations.
To avoid salinity and distance the washings or not having to reach them, it is best to do short and frequent waterings.
Plantae sensors indicate the degree of humidity and conductivity in real time and therefore the need for irrigation and the risk of salts. In this way, there are no drought intervals around the plant in addition to absorbing it in a more continuous way and this means that with evaporation the salts accumulate much less.
To all this we can add a padding that prevents evaporation.
In cases of excessive accumulation, a drainage can be made with ditches that receive the salts when washing.
At present, different Universities carry out studies on in vitro embryo cultures that are resistant to salinity, especially the olive tree. The Picual variety is quite resistant to salinity but other varieties such as chamomile are more sensitive.
Studies in the creation of these plants in vitro in the nursery can shorten the problem and if it is also accompanied by a control, the effect of salinity in the short and long term can be reduced to a minimum. There are also studies that indicate that in the first years, salinity does not affect growth or production, but in the long term there is a significant decrease in growth and fruit.
The intensive and super-intensive olive varieties are usually Arbequina and Arbosana, which in traditional cultivation are not usually sensitive to salinity because irrigation is scarce. When the cultivation is intensive or super-intensive, irrigation in times of heat intensifies and the problem appears if we do not control it properly.
For this reason, the control by humidity sensors, in addition to saving water and energy, will reduce salinity and therefore favor the production and duration of the plantations.