Adopting a Robotic pH Instrument for Soil and Soil-Buffer pH Measurements in a Soil Test Laboratory

Abstract

Optimum software settings were evaluated to minimize time of analysis without sacrificing data quality on an AS-3010D LabFit robotic instrument. There was little to no difference between soil and soil-buffer pH values measured via manual methods and LabFit analysis with four software settings. A setting for routine laboratory analysis was determined by evaluating r2 values from a comparison of LabFit versus manual measurements. Settings for routine analysis were adopted as follows: 5 s for sample delay time, 60 s for maximum sample time, 10 readings for stability, 0.02 for pH stability, 0 s for buffer run delay, and probe rinsing after every 40 samples. These settings were evaluated on 2933 Kentucky soil samples where robotic versus routine analysis of soil and soil-buffer pH resulted in r2 values of 0.94 and 0.82 for soil pH and soil-buffer pH, respectively. The results validated the utility of robotic instruments for soil pH analysis.