Answer: Increased soil salinity levels can greatly effect plant growth and production. Some soils are naturally high in salinity but most salinity problems on farms are increased by farm practices. In arid regions of the country, irrigation water can build salinity in soils. Adding fertilizers containing salts can also built up salinity levels if there is not enough rain to flush the soils, or in high tunnel production where soils are not exposed to the weather.
Electrical conductivity of soil or irrigation water is used as a means of testing levels of salinity. This is usually measured in deciSiemens per meter (dS/m) and the higher the number, the higher the salinity. You can buy an electrical conductivity meter for about $150.
In general, levels above 1 dS/m are getting high for vegetable crops, but specific thresholds for different crops can be found in the University of Vermont Center for Sustainable Agriculture publication titled High Tunnels. It is available at www.uvm.edu/sustainableagriculture/Documents/HighTunnels.pdf. Pages 56 and 57 of this publication talk about the causes of soil salinity, testing, salinity levels that effect different crops and possible solutions. The chart on page 56 lists the threshold salinity level for individual crops before production starts to drop. Salinity is talked about here in the context of high tunnel production in the east, but the thresholds are the same wherever you are growing crops.
Colorado extension also has an excellent fact sheet on soil salinity, titled Managing Saline Soils. It discusses the causes of soil salinity, its effect on plants, and how to manage soil salinity. You can access this fact sheet at www.ext.colostate.edu/pubs/crops/00503.html.
To learn more about healthy soil, check out the Soils & Compost section of the ATTRA website at https://attra.ncat.org/soils.html.
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