Salinity
Class: Abiotic Stress
Salinity is a major abiotic stress that reduces plant growth and plant yields, while affecting most of the biological processes that take place within plants. The subject of salinity is poorly understood among growers, leading to a handful of false statements. The following are important and essential key facts that every grower should know:
What is salinity?
Salinity is the amount of salt dissolved in water. Salt is a solid crystalline composed of ions. The concentration of salts within soil or water correlates with the medium’s electrical conductivity.
Salts in high concentrations can severely damage plants, but not all salts are created equal. Each type of salt has its own properties and interactions with different plants. For example, potassium chloride (KCl) is a common fertilizer, is less toxic to plants, and has a wider range of levels that plants can tolerate compared to other salts. So, while some levels of a specific salt can be beneficial and essential to plants, other levels can inflict damage.
Symptoms in a nutshell
Toxic levels of sodium chloride (table salt) cause salt damage to crops. High concentrations of sodium chloride can have a devastating impact on seed germination and create osmotic stress causing plants to become water deficit. High concentrations of sodium chloride can also cause ion imbalances and toxicity that is seen on older leaves as burned tips, which can develop into more extended necrosis.
Where is all that salt coming from?
Salts are all around us; they occur naturally within soil and water. Some soils are considered rich in salts, such as clay soil, while other soils will have lower levels, such as sand that does not easily attach to salts. A common scenario that farmers have to deal with is the drifting of nearby salts to the roots zone of plants after heavy rain.
An unnatural contributor to the amount of salt in the soil is the addition of synthetic fertilizers and organic compounds that gardeners and farmers use throughout the year. Fertilizers are basically salts and when salts are added in reasonable amounts, they will have a beneficial effect on plants. In most cases, adding fertilizers to irrigation water will only raise the electrical conductivity by an insignificant amount.
Salinity from irrigation: Almost all water contains dissolved salts. When plants consume water, salts are left behind and eventually begin to accumulate. It is important to know that salinity from irrigation water is greatly increased by poor drainage and the use of saline water that can be suitable for some plants.
Control measures
First line of defense is prevention: Check the level of salts in the designated soil before planting. Plan in advance, taking into account crop susceptibility to sodium chloride, soil structure and characteristics, and the quality of your water source. If necessary, initiate preventive measures that can improve overall drainage or initiate several preplanting, high volume irrigation executions in order to wash and push aside salts.
Monitoring: Keeping track of electrical conductivity values of irrigation water and regularly searching for visual symptoms of salinity - especially after heavy rains. This will improve your response time and allow you to react before serious damage occurs.
Note that stopping or significantly reducing your regular (balanced) fertilizing schedule probably will not have an effect on the situation; it may actually cause more harm, as essential nutrients become deficient.
Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.