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A system developed by Dr John Dell , professor of electrical engineering at the UWA, to track missiles for the US military is providing the foundation for the development of equipment that can rapidly test physical, chemical and some biological soil properties.

Dr Dell's data collection device uses infrared spectroscopy, however it differs considerably from the infrared spectrometers found in the laboratory.

Basically a spectrometer shines a beam of light, consisting on infrared wavelengths, and measures the wavelengths that are reflected from the surface of the object. The reflected data is called the spectra. The reflected wavelengths provide signature for specific properties, for example organic matter (OM) reflects different wavelengths to clay.

"Laboratory equipment for measuring mid and near infrared is relatively large and expensive, and contains sensitive moving parts." Dr Dell says.

"Using microelectronic technology we have reduced the size of spectrometer to about the size of your thumbnail."

The revolutionary spectrometer design has no moving parts. Instead a small tuneable filters allow all the near infrared (NIR) and some of the mid infrared (MIR) wavelengths to be detected by a microspectrometer.

Having no moving parts the microspectrometers are robust and unaffected by movement and vibration, which are the problems faced by conventional spectrometers. Their size and design makes them relatively cheap and they are able to acquire data rapidly. All this are factors required for a rapid in-paddock soil sensor.

"We know our microspectrometer design can reliably and repeatedly collect spectra for moving objects or while in motion, but we have yet to establish if it can detect the spectral information required from a soil sample."

Laboratory equipment gathers spectra data at a finer resolution and for a greater range of wavelengths than the microspectrometer. The next faze of Dr Dell's research is to establish if the microspectrometer is able to provide sufficient data for useful assessment for soil characteristics.

"Calibration for soil characterisation based on MIR and NIR data are still being developed and there is much modelling required before we will know if the device is sufficiently sensitive.

"We are working in parallel with several other GRDC-funded projects looking at the use of infrared spectroscopy for soil analysis".

If you are concerned about the vulnerability of a row of thumbnail-size spectrometers mounted on the harvester or the spray boom, Dr Dell is confident there is no need to worry, as the final device, including the box holding the electronics, would be at least as large as a cigarette packet. However, as the microspectrometer does not penetrate deep into the soil, it is more likely to be used in conjunction with automated soil-coring equipment to provide on-the-spot readings to depth.