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Sodium Adsorption Ratio Screening Procedure for Soils Using pH and Electrical Conductivity
Author(s) -
Munk Lewis P.
Publication year - 1992
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1992.03615995005600040019x
Subject(s) - soil water , sodium adsorption ratio , adsorption , electrical resistivity and conductivity , chemistry , conductivity , sodium , analytical chemistry (journal) , soil science , environmental science , environmental chemistry , physics , ecology , organic chemistry , drip irrigation , quantum mechanics , irrigation , biology
Soils with sodium adsorption ratios (SAR) <10 are generally considered to be below the threshold for potential Na hazard. The impetus for developing this screening procedure was to reduce the resources dedicated to determining precise SAR values in situations when simply knowing that the SAR is below the designated threshold is sufficient. The model was developed using 1000 samples and validated on a 24 000‐sample data set from two different laboratories operating in the western USA. The screening procedure uses empirically derived combinations of saturated soil paste pH (pH s ) and extract electrical conductivity (EC e ) to predict if the SAR is above or below 10, or whether Ca + Mg and Na must be analyzed to determine the SAR. For some combinations of pH s and EC e , the ratio of Ca + Mg to estimated total cations [ETC = EC e (10)] is used to decide whether Na must be analyzed. On average, the model incorrectly predicted that the SAR was <10 when the actual value was > 10 in only six out of 1000 samples. In addition, about 20% of the samples required Ca + Mg and Na analyses when the SAR was < 10. For the data sets tested, the screening procedure could have reduced the number of Ca + Mg and Na analyses by 50% with little loss of information about the potential Na hazard of the soils.