Comparing Field Measurement Methods of Soil pH and Moisture for Use in an Urban Site Assessment.

Accurate and practical field measurements of urban soil moisture and pH can be challenging to acquire. These measurements are important for urban soil assessments that can be used to identify site quality and observe the efficacy of management actions. An experiment was conducted on twenty-two sensors (eleven moisture, seven pH, and four combination) of varying expense ($10-$750+) and measurement methodology (soil electrical conductivity (EC), time domain reflectometry (TDR), frequency domain reflectometry (FDR), and pH glass electrode). Sensors were tested on four soil textures (loamy sand, sandy loam, silt loam, and clay) at three moisture contents (air dry, near 50% field capacity, and near field capacity) and evaluated against a standard determined using either the thermogravimetric method, or a glass electrode pH sensor. The hypothesis tested was sensors that use TDR and FDR methods or a glass electrode are more accurate than those measuring soil EC. This is maybe due to the quality of the instruments and the influence of soil salt contents and is based on observations suggesting that urban soils are highly variable in salt content both seasonally and as a result of management actions. Sensors measuring soil pH were evaluated using Pearson's Correlation Coefficient. Sensors using the EC method showed no significant correlation (P > 0.1, r <0.2) to the standard. Glass electrode sensors where found to be significant (P <0.0001) and strongly correlated to the standard (r >0.95). Moisture sensors were evaluated using Lin's Concordance Correlation. Most soil EC sensors were weakly correlated to the standard (P_c <0.40) with the exception of two sensors (P_c >0.70). Sensors using TDR and FDR methods were found to be highly correlated (P_c 0.76, 0.89 respectively) to the standard. These findings provide valuable insight into which sensors can best be used to assess urban soils. The poster will also cover how these sensors can be used as part of an urban soil assessment.