Field measurements of soil pH and lime requirement using an on-the-go soil pH and lime requirement measurement system

Further adoption and implementation of precision agriculture (PA) requires the development of proximal on-the-go sensing systems. Recently, an on-the-go Soil pH and Lime Requirement Measurement System (SpHLRMS) prototype was developed in a collaborative project between the Australian Centre for Precision Agriculture (ACPA), the Swedish Institute for Agricultural and Environmental Engineering (JTI) and Computronics Holdings Ltd. The system is made up of a soil sampling and sieving mechanism, a soil analytical component with a PH ISFET (Ion Sensitive Field Effect Transistor) used to measure changes in soil pH and data collection and measurement algorithms. The system measures soil pH and lime requirement. This paper reports the results from field testing of the first prototype of the SpHLRMS. The accuracies of soil PH measurements in 0.01M CaCl2 and in deionised H2O were 0.37 and 0.6 PH units, respectively. The accuracy of estimated lime requirements was 0.6 Mg/ha. A number of improvements to the system are still needed but these first results are promising.