Dr Uta Stockmann¹, Dr Mark Farrell², Mr Thomas Carter², Mrs Seija Tuomi¹, Mr Shaun Krawitz³, Ms Brigitte Small³, Dr Ben Macdonald¹

¹CSIRO Agriculture and Food, Black Mountain, Canberra, Australia, ²CSIRO Agriculture and Food, Waite Campus, Urrbrae, Australia, ³School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia

Intensive agricultural production systems have had a dramatic impact on the status of pacific island soils, and have changed their soil physical, chemical and biological function. Their ability to deliver crucial ecosystem services, including soil organic carbon storage, soil nutrient delivery and soil water holding capacity has been affected. The state of the soil is a key factor in farm value on pacific islands and therefore warrants monitoring to ensure the sustainability of the soil resource for future generations. However, traditional soil laboratory techniques are expensive to use for soil monitoring purposes and also hard to access at times, because of remoteness of the islands and limited laboratory capacity. Soil spectroscopic techniques offer cost-effective and rapid analyses, and hand-held, field-portable devices have the potential to be used for instantaneous soil analysis results. Spectral techniques operating in the X-ray, vis-NIR and MIR part of the electromagnetic spectrum offer the ability to predict a range of soil properties of agronomic importance including soil organic matter, pH, soil texture and macro-, micro and trace-nutrients. Here, we conducted a study to assess the suitability of soil spectral techniques to quantify aspects of soil fertility for allophanic soils of several agricultural plots on Tongatapu island, Tonga. Locations were chosen to also allow for comparison of the impact of management practices on the soil’s status. This work will contribute to building a soil spectral library for pacific island soils, to make possible the use of spectral devices to gain valuable soil information.