Abstract
Highly soluble salts are undesirable in agriculture because they reduce yields or the quality of most cash crops and can leak to surface or sub-surface waters. In some cases salinity can be associated with unique history, rarity, or special habitats protected by environmental laws. Yet in considering the measurement of soil salinity for long-term monitoring purposes, adequate methods are required. Both saturated paste extracts, intended for agriculture, and direct surface and/or porewater salinity measurement, used in inundated wetlands, are unsuited for hypersaline wetlands that often are only occasionally inundated. For these cases, we propose the use of 1:5 soil/water (weight/weight) extracts as the standard for expressing the electrical conductivity (EC) of such soils and for further salt determinations. We also propose checking for ion-pairing with a 1:10 or more diluted extract in hypersaline soils. As an illustration, we apply the two-dilutions approach to a set of 359 soil samples from saline wetlands ranging in ECe from 2.3 dS m-1 to 183.0 dS m-1. This easy procedure will be useful in survey campaigns and in the monitoring of soil salt content.
Highlights
Salts commonly occur across the Earth’s surface
The sampled soils were either bare or supported halophytes at the less inundable positions. This is in agreement with the hypersalinity of the studied soils expressed by the mean ECe = 72.3 dS m-1 of the 359 samples studied and their range from 2.32 dS m-1 to 183.00 dS m-1 (Table 1)
Ten samples were below the ECe threshold 4 dS m-1 for saline soils, while 300 samples had ECe > 16 dS m-1,5 the threshold for very strongly saline soils
Summary
Most salts needed for life are imbibed by plants from the soil. Fertile soil provides an adequate content of salts needed by plants. Soil salts at the Earth surface are dissolved and redistributed across the landscape, leading either to salt leaching or accumulation at specific geomorphic positions. Saline soils are more frequent in regions where evaporation exceeds rainfall. Human actions can salinize or desalinize soils, sometimes in only a few years. Examples of such include the clearing of lands in Australia, or irrigation with brackish water pervasive in some countries. Changes in soil salt contents have been measured or surmised at several temporal scales [1,2,3,4]
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