For agricultural (or any plant) production, salts are necessary in the form of plant nutrients, but become toxic in excessive quantities. Salts such as calcium (Ca), magnesium (Mg), and sulfur (S) are necessary for plant growth, but saltwater intrusion can raise these levels higher than (upland) plants are adapted to. These excess salt reduce the ability of plants to absorb water, causing dehydration (see bottom of the page). These salts may also compete for uptake into the plant, altering nutrient balances. A well known example is how excess potassium (K) can reduce Mg uptake into grasses.
Soil quality can also be reduced with excessive salts, particularly sodium, which may cause crusting reducing water infiltration and the ability of the germinating seed to push through the soil surface.
Sodium (Na) is a separate issue, as it can cause the issues noted above (reduced water uptake) but is also toxic to most plants at increased concentrations in the soil. Levels of Na and chloride (Cl) from salty or brackish water can quickly raise levels on the edges of coastal fields. Normal Na levels in soil can be 5-40 ppm, but have been observed at 1000 ppm following saltwater intrusion.UD
UD SWI Extension Factsheets:
Salt Measurements and Soil Classifications
For an overview of salts in agriculture, you can watch this webinar from the Mid Atlantic Women in Agriculture series. A pdf copy of the slides is available here: Soils and Salts: From Fertilizer to Tidewater.
These corn plants along the edge of a tidally influenced ditch didn’t germinate or grow in some parts of the field, but are also suffering from excessive dry conditions. Droughts will be worse with excess salts in the soils.
