Sensor survey methods, including electromagnetic induction and gamma-radiometrics sensor survey systems, are available to be used for field survey, to map soil variability, and for zoning. This field survey approach aims at early detection of spatial soil variability and sampling design optimization.
As part of a trans-Tasman collaboration supported by a New Zealand Government Global Research Alliance project, CSIRO, in collaboration with Manaaki Whenua, designed and developed the Soil Condition Analysis System (SCANS), a multi-sensor platform, deployable in the field that combines a Vis–NIR spectrophotometer, a gamma-ray densitometer, and a CCD camera. SCANS is currently operating in our Palmerston North Soil Carbon Laboratory. The SCANS platform allows high resolution scanning of intact soil cores in their field condition, with no pre-processing required. The densitometer measures bulk density and the Vis-NIR spectrometer simultaneously collects spectra for predicting a range of soil properties (Fig. 3). The rapid acquisition of bulk density data enables direct volumetric measurement of soil components. We can, therefore, predict volumetric soil carbon from which we estimate soil carbon stocks. In addition, through the analysis of the spectra, we can estimate other properties such as pH, cation exchange capacity, and clay content. We are currently employing the SCANS in different projects, from soil organic carbon stock assessments at national scale to soil carbon sequestration studies at paddock scale, in a worldwide effort to mitigate climate change. And this is just the beginning, because the spectral profiles from analysed soil cores can help investigate other soil characteristics, such as phosphorus retention and plant available nitrogen, to provide critical new point data to national soil mapping and other research efforts.