Premium
Improving Estimates of Soil Salinity from Saturation Paste Extracts in Calcareous Soils
Author(s) -
Amakor Xystus N.,
Jacobson Astrid R.,
Cardon Grant E.
Publication year - 2013
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/sssaj2012.0235
Subject(s) - saturation (graph theory) , calcareous , salinity , soil water , soil salinity , chemistry , soil science , environmental chemistry , total dissolved solids , environmental science , environmental engineering , geology , mathematics , paleontology , oceanography , combinatorics
In the arid and semiarid western United States, accurate measurement of soil salinity by electrolytic conductivity can be a challenge due to the formation of ion pairs in the high ionic strength soil solutions that affect estimates of the total quantity of ions in solution. Continued underestimation of total dissolved solids (TDS) threatens the long‐term sustainable management of irrigated agricultural lands in regions faced with a threat of soil salinization. This study aims to improve estimates of soil salinity in calcareous soils. We hypothesized that saturation paste extracts can be diluted to a point where ion pair formation is minimized, so that the electrical conductivity (EC) of the saturation paste extract (ECe) can be used to more accurately predict soil salinity. Results of an analytical conceptual model using salt solutions and ion speciation modeling of these solutions suggest that 0.03 to 0.05 dS m –1 is the optimal EC range beyond which dilutions produce negligible decreases in EC and where approximately 99% of the ion species occur as free ions. Diluting soil saturation paste extracts to conductivities <0.05 dS m –1 (e.g., in our samples by a factor of approximately 1000), minimized ion pairing as supported by analysis of ions in solution, solution speciation with visual Minteq, and comparisons of calculated TDS (in mmol L –1 ). To therefore improve the estimates of salinity in calcareous soils, we recommend diluting the saturated paste extracts to EC < 0.05 dS m –1 , computing TDS from the diluted EC values, and then multiplying the TDS by the dilution factor.