How does salinity affect plant growth and yield?
Stress in the form of salinity is the most limiting environmental factor affecting plant growth in regions where rainfall is limited (Parida and Das, 2005). Salts limit plant growth via several pathways. First, saline soils reduce a plant’s ability to absorb water. “Osmotic stress symptoms are very similar to those of drought stress, and include stunted growth, poor germination, leaf burn, wilting and possibly death” (McCauley and Jones, 2005). These symptoms, similar to drought stress, occur even when water is present in the soil. In addition to affecting a plant’s ability to take up water, excess salinity can affect nutrient availability and uptake, and it can cause toxicity issues from sodium and chlorine (Evelin et al., 2009).
The effects that salt have on plants vary depending on the type of crop being grown, the amount of salt, and the type of salts in the soil. The presence of salts in the shallow layers of the soil profile will have a greater negative impact than those at layers further down in the profile, due to their proximity to plant roots. Salt tolerance varies greatly from crop to crop. Carrots and strawberries, for example, are sensitive enough to suffer yield and growth losses in soils considered to be “very slightly saline,” while asparagus and chard are tolerant to much higher levels of salts. Each crop species has a corresponding level of tolerance to salinity and, beyond this level, growth and yield begin to diminish. Many plants will not display negative effects of salinity stress; thus, observational analysis may not be sufficient to determine if salts are affecting the yield of a particular crop. Salt stress can darken leaves and restrict growth, but plants may otherwise appear healthy (Maas and Grattan, 1999).
You’ll benefit from reading the new ATTRA publication Saline and Sodic Soils: Identification, Mitigation, and Management Considerations, which explores this topic in detail. It includes a table showing crop-specific tolerance levels.
Evelin, H., R. Kapoor, and B. Giri. 2009. Arbuscular mycorrhizal fungi in alleviation of salt stress: a review. Annals of Botany. Vol. 104, No. 7. p. 1263–1280.
Maas, E.V. and S.R. Grattan. 1999. Crop yields as affected by salinity. In: R.W. Skaggs and J. Van Schilfgaarde (eds.). Agricultural Drainage. Number 38 in the series Agronomy Monographs. American Society of Agronomy, Madison, WI.
McCauley, Ann and Clain Jones. 2005. Salinity and Sodicity Management. MSU Extension Service Continuing Education Series. 4481-2.
Parida, A.K. and A.B. Das. 2005. Salt tolerance and salinity effects on plants: a review. Environmental Toxicology and Environmental Safety. Vol. 60, No. 3. p. 324-349.