Loading...
Please wait, while we are loading the content...
Similar Documents
Spatial Variability of Saline and Sodic Soils in the Black Glaciated Region of the Northern Great Plains, USA
| Content Provider | Semantic Scholar |
|---|---|
| Author | Owen, Rachel K. |
| Copyright Year | 2015 |
| Abstract | Electrical conductivity (EC) is an important index for assessing salt affected soils and can also be used to predict the total soluble cations (TSC) in soil, but the relationship developed by Rhoades (1982) of EC x 10 = TSC is not accurate for soils affected by groundwater salinity in the Northern Great Plains. Therefore, the objectives of this study were to establish linear models for EC and TSC using selected South Dakota (SD) and North Dakota (ND), USA soils. Soil samples (n = 1245) were collected from four sites in SD and ND and analyzed for EC and soluble sodium (Na+), calcium (Ca2+), and magnesium (Mg2+). TSC was the sum of soluble Na+, Ca2+, and Mg2+. Results showed that the linear relationship between EC and TSC was TSC = 13.54 *EC – 0.29 (R2 = 0.88), which held true over EC values 0-18 dS m-1 and on a field, state, and regional scale. By establishing an accurate relationship between EC and TSC in this region, soil testing laboratories, crop consultants, soil scientists, government agencies, and educators have a simple way to relate EC to TSC and can more efficiently assess salt affected soils. INTRODUCTION Globally, electrical conductivity (EC) is a common index in assessing soil salinity. The ability of a soil solution to conduct electricity is directly related to the total amount of soluble cations (TSC) and anions (TSA) contained in a solution. EC readings 11 can be affected by soil moisture content (Vaughan, 1995), texture (Sudduth, et al., 2005), and mineral composition (US Salinity Laboratory Staff, 1954). The EC has been used to estimate the total dissolved cations in the solution. In 1954, the US Salinity Laboratory established the relationship of approximately 10:1 for EC (dS m-1) to TSC (mmolec L-1) , and since, this ratio has been used to simplify other salinity calculations, especially those involving the relative proportions of monovalent and divalent cations in the soil, and can serve as a quick field scale assessment of salinity issues (Rhoades, 1982, US Salinity Laboratory Staff, 1954). The total dissolved cation value is used to calculate the sodium adsorption ration (SAR). SAR is calculated using Equation 2.1: (2.1) where SAR is the sodium adsorption ratio, [Na+] is the concentration of soluble sodium, [Ca2+] is the concentration of soluble calcium, and [Mg2+] is the concentration of soluble magnesium. In this calculation, the EC×10 value is used to calculate the approximate amount of Ca2+ + Mg2+ + Na+ contained in solution. The Ca2+ and Mg2+ is determined by subtracting Na+ from the EC×10 value. This approach is based on the salt affected soils in the 17 Western States and Hawaii (US Salinity Laboratory Staff, 1954). Some crucial differences exist between the soils studied by Rhoades (1982) and the US Salinity Laboratory Staff (1954) and the saltaffected soils in the Central and Southern Black Glaciated Plains in South Dakota and North Dakota, USA (MLRA Regions 55B and 55C [NRCS, 2014a]). One of the primary differences is the source of the salts. In the Northern Great Plains, salinity occurs due to Mg 2 / 12 the subsurface transport of salts with capillary water to the surface soil, whereas in the arid and semi-arid regions of the west salts are provided with irrigation water. The soils of the Black Glaciated Plains were formed in till that overlays Cretaceous marine shale from a prehistoric ocean, so groundwater brings salts from the shale bedrock to the glaciated surface soils (Daniels, 1987). These critical differences suggest that salt identification criteria developed for surface irrigated agricultural systems might have limited applications for the Northern Great Plains. The objective of this study was to establish a relationship between EC and TSC that would fit soils throughout the Central and Southern Black Glaciated Plains of South Dakota and North Dakota. In laboratory studies done in South Dakota, with soils affected by groundwater salinity, the 10:1 relationship between EC and TSC did not hold true (Wilkerson, et al., 2014). Studies done in Canada, where groundwater salinity is prevalent as well, have also found that the original relationship does not work and have created new models for relating EC and TSC (Chang, 1983). There are two main reasons to establish a robust relationship between EC and TSC. First, indirect measurements of EC, such as electromagnetic induction with EM38 (Geomatrix Earth Science Ltd.) or Veris (Veris Technologies, 2014) technology, are quick ways to assess soil salinity on a field scale (Rhoades, 1982). Next, research institutions and soil testing laboratories can use the relationship between EC and TSC to estimate the sodium adsorption ratio (SAR). |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://openprairie.sdstate.edu/cgi/viewcontent.cgi?article=2087&context=etd |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
