Preliminary experiments towards the evaluation of a suitable soil sensor for continuous, 'on-the-go' field pH measurements

1997

R.A. Viscarra Rossel and A.B. McBratney
Australian Centre for Precision Agriculture, McMillan Building A05, The University of Sydney NSW 2006, Australia.

Precision Agriculture '97, Proceedings of the First European Conference on Precision Agriculture, Warwick, 7-10 September 1997, pp. 493-501.

ABSTRACT

A required step in the evolution of agricultural site-specific management systems is the development of real-time, continuous sensors and scanners to more efficiently and economically obtain comprehensive and precise soil and crop attribute variability information. Soil pH was chosen as an initial attribute for which to develop such technology, and a preliminary evaluation of four potentiometric pH sensors, namely a glass electrode, a glass micro-electrode, a metallic electrode and an Ion Sensitive Field Effect Transistor (ISFET), was conducted. The pH range, fragility, precision and response time of each sensor was investigated, response time being the most critical property. The ISFET sensor proved to be the most suitable sensor in terms of its ruggedness and its fast response time. Further experimentation conducted with the ISFET sensor involved testing its response time at two different solution-stirring rates and two soil:solution ratios. The speed of response increased with increased stirring speed, and when a higher soil to solution ratio was used.