Monitoring Soil Salinity: A Laboratory Assessment of Soil-Water Ratios, In-Situ Sensors, and Spectroscopy
AuthorTate, Amanda Elise
AdvisorVerburg, Paul S
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In arid and semi-arid regions where evapotranspiration exceeds precipitation, soils often undergo salinization over time, which can negatively affect soil structure and crop yield. Cost-effective and accurate methods for measuring soil salinity are needed by producers and land managers to allow them to make decisions about salt management. Our project seeks to assess and, when possible, establish accurate conversion regressions between three commonly used methods for measuring salinity; soil:water extracts, in-situ capacitance sensors, and spectroscopy. Small-scale agricultural producers and land managers can benefit from the sensor measurements while land management agencies and large-scale agricultural producers could benefit from the spectral assessment. It was found that soil similarities should be considered when choosing a regression equation. The 1:1 soil:water ratios showed best correlation to effective electrical conductivity (ECe) as measured using the saturated paste method, the standard method to measure soil salinity. In-situ sensors may be best suited to monitor temporal changes in bulk electrical conductivity (ECb) and volumetric water content (VWC) but correlations between ECb and ECe were typically poor. Results indicate that methods of assessing salinity utilizing spectroscopy would be unreliable due to soil moisture spectral interference and lack of salt spectral features.