Salt occurs naturally in soil. Ordinarily, the forces of nature ensure that salt leaches at a regular rate below the root zone of most plants, even as ground water picks up more, resulting in a consistent range of soil salinity that doesn't harm plant life. In agriculture, however, repeated tilling creates a hard-pan underground just below the roots that traps salt, even as irrigation brings more salinity to the soil. With close to 20 percent of cultivated land in the U.S. experiencing issues with elevated salt concentrations, farmers are increasingly looking for crops that can tolerate at least moderate salt intake. Trials with rye grasses are encouraging in this regard.
Salt Robs Plants of Nutrients
The two most common harmful salts in soil are sodium chloride (NaCl) and sodium sulfate (NaSO4). They dissolve in water, making the sodium bioavailable, and which plants readily take in through their roots. The sodium enters regions intended for the chemically similar potassium (K) mineral, robbing the plant of an element needed to catalyze dozens of cell functions related to growth. There really are no crops that need salt to thrive, but some plants can resist the negative consequences better than others, including some varieties of rye grass.
Rye Grass and Drought
Another devastating effect that salt has on plants is to mimic drought conditions for the plant, even if there is sufficient moisture in the soil. When salt is present, plant cells are under osmotic pressure to lose water. Water maintains plant cell rigidity, so leaves and stems literally sag if there isn't enough water. Plants fight back by closing the stomata in their leaves, which blocks some water vapor loss through transpiration. However, this also results in less carbon dioxide gas exchange, which plants need for photosynthesis.
How Rye Grass Copes with Salt Exposure
Because rye grass is already drought-tolerant, it is able to withstand water loss brought on by salt for a longer period of time than many crops. A high calcium content in the stems and leaves also prevents most wilting, which could cut off plant circulation.
Hardy Rye Grass Strains
Ryegrass is called an "outbreeder" by scientists, meaning that there is quite a bit of genetic variety within the type. Research is ongoing as to which specific strains best resist salt and at what concentrations. "Penguin" and "Hawkeye" are among those varieties that show the best promise, with good germination in salt concentrations up to 12,000 parts per million.
Ways of Mitigating Salt Exposure
Salt solubility is how it so readily gets into soil and also the means by which it can be flushed out of soil. Good drainage is crucial, so salt can be leached out of the root zone in surface soil. Clean, saline-free water lowers the salt concentration of soil as well. Extra potassium in fertilizer allows that nutrient to be found by plant roots more readily, so fewer sodium atoms can displace it in the cells.