Following an irrigation event, water will evaporate from the soil surface. This is a natural process known as salinization where salts are left behind in the soil and accumulate over time. Both surface water and groundwater contribute to this situation. For groundwater, a rise in the water table can push salts nearer to the roots of growing plants. Regardless of the water source, the effects of salinization tend to get worse when temperatures heat up and evaporation increases.
Most agricultural crops do not grow well on salty soils because toxic effects from salts negatively impact plant physiology. In fact, salts decrease the rate and amount of water that plant roots can take up from the soil. Normal, healthy soils have a chemical and physical balance with good structure which allows for optimum water and gas exchange. When soil has a high concentration of salinity, structure is compacted and causes a reduction in soil water potential. This decreases plant metabolic activities and stunts growth, reduces photosynthetic activity and leads to oxidative stress. These stresses can be severe enough to result in plant death.
Certain plant species are more tolerant of saline soils but many of the specialty crops grown in California are very sensitive to high salt concentrations. Those sensitive crops include almonds, citrus, stone fruit and pome fruit just to name a few.
There are a variety of practices that are effective in reducing salt concentrations in the soil. A standard practice is using a leaching fraction during irrigation applications to push salts out of the root zone. A clean water source is preferable, but a leaching fraction can be effective even when using saline water. Soil amendments are also used to displace sodium that is attached to soil particles in order to replace it with calcium or magnesium.
Gypsum (calcium sulfate), lime (calcium carbonate), dolomite (calcium and magnesium carbonate) or a strong acid such as sulfuric acid are common treatments for mitigating salts. These amendments are generally post-harvest applications. The calcium-based treatments tend to require long periods of time to break down with the help of winter rains for leaching salts. Acid treatments in large volumes pose a risk to actively growing tissues so applications are best in the winter or during dormancy. This leaves an in-season void for addressing soil salinity while fruits and nuts are actively developing.
GAR Bennett carries a variety of products and programs that support plant development under conditions of salt stress. Contact your PCA today to help alleviate the stress on your crops!