Soil electrical conductivity

Soil electrical conductivity

The electrical conductivity (EC) of the soil is used to calculate the amount of salts in the soil (salinity of soil). It is an important criterion for assessing soil health. Crop yields, crop compatibility, plant nutrient availability, and soil microorganism activity are all affected. Excess salts stifle plant growth by disrupting the soil-water equilibrium. Excess salts in soil occur naturally in arid and semiarid environments. Cropping, irrigation, and land management can all contribute to an increase in salt levels.

Although EC does not directly detect individual ions or salt molecules, it has been linked to the concentrations of nitrates, potassium, sodium, chloride, sulfate, and ammonia. Determining EC for specific non-saline soils can be a quick and low-cost method of determining the amount of nitrogen (N) available for plant growth.

Factors Affecting Soil Electrical Conductivity (EC)

Soil minerals, climate, and soil texture are all natural factors that influence EC and cannot be altered. When minerals and rocks disintegrate, salts form. In areas where there is a lot of rain, soluble salts from minerals and rocks are flushed below the root zone, eventually ending up in deep groundwater systems or streams that transport salts to the ocean. In contrast, soluble salts are more likely to accumulate and remain near the soil surface in arid areas or areas where less rainfall occurs or saline irrigation water is used, resulting in high EC.

Measuring the EC of the Soil

Electrical conductivity is measured in milliSiemens per meter (mS/m) and refers to a material's ability to conduct (transmit) an electrical current. Measurements of electrical conductivity can also be expressed in deciSiemens per meter (dS/m), which is a 100-fold increase over milliSiemens per meter. It is calculated by taking a soil sample, making a saturated paste with deionized water, extracting the water, and measuring the EC of the extracted solution. The activity of soil microorganisms decreases as EC increases. Significant soil processes such as respiration, residue breakdown, nitrification, and denitrification are all impacted. High sodium salt concentrations in soil cause additional problems such as poor soil structure, poor penetration or drainage, and toxicity to many crops. Each crop has a different salt tolerance.

Cation exchange capacity

The total capacity of soil to hold exchangeable cations is known as cation exchange capacity (CEC). CEC is a natural soil property that is difficult to significantly alter. It affects the soil's ability to retain important nutrients and acts as an acidification buffer. CEC levels are typically higher in clay-rich soils. Organic materials have a very high CEC. Sandy soils rely heavily on the high CEC of organic matter for nutrient retention in the topsoil. Electrostatic force causes negatively charged sites on the surfaces of soil's clay mineral and organic matter components to absorb and hold positively charged ions (cations). Because many nutrients exist as cations, this electrical charge is critical to nutrient provision to plants (e.g. magnesium, potassium, and calcium). Soils with a high negative charge retain more cations and are thus more fertile; however, productive crops and pastures can be grown on soils with a low CEC. A more important consideration is whether the net amount of Ca or K in the soil is sufficient for plant growth. The addition of organic matter increases soil CEC but takes many years to take effect.