Managing Saline and Sodic Soils and Irrigation Water Burdette Barker, USU Extension Irrigation Specialist Grant Cardon, USU Extension Soils Specialist Matt Yost, USU Extension Agroclimate Specialist Melanie Stock, USU Extension Urban and Small Farms Specialist Earl Creech, USU Extension Agronomy Specialist Jody Gale, USU Extension Associate Professor
Introduction
Salt is important in plant and soil management. Excessive salt concentrations in soil can cause water to be less available to plants because of the osmotic forces of salt in the soil water. Excessive concentrations of some salt ions can also be toxic to plants. In agricultural soils and irrigation water, salts are typically described in two ways: 1. Salinity, or total salt concentration, and 2. Sodicity, or the concentration of sodium relative to other cations (positively charged atoms or compounds). Understanding the effect of both salinity and sodicity on plants and soils and the appropriate management and reclamation practices can improve crop yield and the optimal use of crop inputs.
Measures of Salinity
The most common measure of salinity in soils and water is electrical conductivity (EC). For agricultural soils, the EC of the soil extract (ECe) is typically used. The soil extract is obtained by saturating a soil sample with pure water and measuring the EC of water extracted from the sample. This will typically be presented in the following units: • • •
Decisiemens per meter (dS/m). Microsiemens per centimeter (µS/cm; 1 dS/m = 1,000 µS/cm). Retired units of millimhos per centimeter (mmho/cm; 1 mmho/cm = 1 dS/m).
Soil salinity is classified based on EC (Table 1). Soil salinity is typically measured by collecting and sending samples to a lab. While field test meters exist, soil probes that provide EC are typically not an accurate measure of the ECe.
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