As you might have read in our two previous posts (see the end of this article for links), the aim of this Defra-funded ELMS Test and Trial project is to field-test three different soil scanners to understand if they can produce replicable and consistent results against a baseline of traditional methods of soil assessment.
The third scanner was from Hutchinsons, through their Omnia Precision Agronomy service. Hutchinsons use the SoilOptix scanner, developed in Canada.
Like the Precision Decisions scanner, the SoilOptix is non-invasive—it doesn’t have to touch the soil – and is mounted 2ft above the ground. For our scanning trial, it was mounted on a pickup (see below), but it could be mounted on other vehicles, such as orchard tractors, to cope with different cropping patterns. Like the other two scanners, it scans around 12m width and can be driven at around 12 mph, so it can cover the ground quickly.
SoilOptix mounted on a pickup
However, the SoilOptix scanner gathers data very differently from the other two scanners. The Soil Optix scanner measures gamma radiation that is naturally emitted from the soil. Specifically, it measures Caesium-137, Uranium-238, Thorium-232 and Potassium-40. The level of natural gamma radiation depends on different geological and geographical conditions and different soil types will emit differing amounts. For example, Thorium-232 absorbs onto clay so clay content can be mapped using Thorium-232 concentrations. The measurement of these different radionuclides is not affected by soil moisture, compaction, crop cover or cultivation – so the limit to scanning is really whether it is possible to travel over the field without causing damage to the crop.
Yes, it does just look like a pickup in a field but this is soil scanning in action!
Scanning is only part of the process, however. Reference soil samples are also collected, with a minimum of four per field. These soil samples are used to calibrate the results from the scanning process. The soil test result and the scanner information on the relationship between the different emission rates of the different radionuclides is used to produce maps of all common nutrient properties, pH, soil texture, organic matter and CEC, as well as elevation and plant available water.
Nick Strelczuk and the SoilOptix scanner working next to the Tamar on one of the project farms
In addition, for this project, some fields were scanned and sampled under Hutchinson’s premium service to deliver more nutrient factors, including calcium, sodium, manganese, boron, copper, molybdenum, iron, zinc and sulphur. As with the Precision Decisions, results are presented through an online portal where different layers of mapping can be viewed.
Our thanks to Nick Strelczuk from Hutchinsons for all his work scanning for the project – and especially for getting all the fields scanned before the weather changed.