Soil scans: What is possible and what is the benefit?
How can technology help map the soil (better), and what role can soil scans and scanners play in this? The equipment is expensive, and having a soil scan carried out is costly too. On top of that, there are different types of equipment and applications. What is possible, and what is the benefit?
Performing soil analyses in an increasingly automated and rapid way is the idea behind mapping the soil with a soil scan. This can be done while driving using a soil scanner and, thanks to the increasing resolution of satellite images, with ever-greater accuracy from space. In Europe, for example, this includes the Copernicus Sentinel-2 satellite system. Copernicus is a European Union programme in partnership with the European Space Agency (ESA).
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Mapping variability
Gaining insight into soil variability—especially differences in soil type/texture, organic matter (OM), humus content, and pH—is the main driver for performing a soil scan. This makes it possible to vary location and dosage of, for example, crop protection products, fertilizers, and planting and sowing materials. This cannot be achieved through (traditional forms of) soil sampling, in which several soil samples are combined into one mixed sample and analyzed in a lab. However, soil scanning equipment is less capable of mapping (variability in) soil nutrients, although some providers claim to be able to derive such information from soil scans.
Soil scanning equipment has been used on a larger scale in the Netherlands for about 15 years to map agricultural land. However, the technology behind it has long been used in geology and soil research and has proven to be complex. For example, the Austrian manufacturer of the Topsoil Mapper soil scanner (also known as SoilXplorer) went bankrupt last year, after which the technology was acquired by the Austrian company Pessl Instruments.
Erik Eising, a Dutch-Canadian by origin, worked in recent years on the development of the SoilReader soil scanner—a NIR sensor mounted in a coulter that rotates and measures moisture and nutrient content in the soil. The SoilReader should have already been launched, but the associated website is offline and Eising did not respond to an information request.
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Gamma radiation, conductivity and electromagnetism
The unpredictable market was also experienced by Eddie Loonstra of the soil consultancy firm Loonstra & Van der Weide. Starting in 2001 under the name The Soil Company, he pioneered with the soil scanner de Mol. “We were simply too early. At the time, there was not enough global demand in agriculture for the technology and related services,” says Loonstra. Today, together with his partner, he advises on soil use and management in the broadest sense.oord.
Another of Loonstra’s companies, RH AgSystems, has been the successor to The Soil Company since 2020 and develops and supplies RH3S soil sensor systems such as the Optimizer and Surveyor. Both use the same technology as de Mol: passive gamma radiation. This same technology is also used in the soil scanner from North American manufacturer SoilOptix. Loonstra: “Passive gamma radiation measurements are not affected by soil moisture or salt content, unlike conductivity and electromagnetic measurements. That makes our data more reliable”
You do a soil scan and use the data for zoning or for modelling
Loonstra continues: “You can map a soil and process that data into one or more zones, or you can use it for modelling, in which all measured soil points are included in the recommendation. We do the latter. Bear in mind that no soil scan yields absolute values and that the measured data must always be validated with soil samples. We focus on crop cultivation—not on sampling for fertilization, as that doesn’t provide background information about a field.” Loonstra & Van der Weide offer a basic recommendation for liming and a detailed recommendation including insight into certain nutrientn.
Veris opened the market (and eyes)
Since 2011, a “new kid on the block” has been active in the Netherlands: the Veris MSP3 soil scanner from American company Veris Technologies. Vantage Agrometius introduced the device to the Netherlands and set up a soil scanning advisory service together with Agrifirm and several contractors. Today, Vantage Agrometius also supplies the Veris iScan and U3 soil scanners.rs.
“The MSP3 remains the most popular in the Netherlands and is currently used by 7 contracting companies,” says Wouter Wijnmaalen, smart farming service coordinator at Vantage Agrometius. The MSP3 determines the soil’s electrical conductivity (EC) in layers from 0 to 30 cm and 0 to 90 cm using electrically charged discs that pass through the soil. Soil structure and texture (clay, sand, and silt) can be inferred from this EC data. A NIR sensor continuously determines the organic matter percentage, and a soil probe collects soil for a pH measurement.
The U3 is a narrower MSP3 that performs stationary pH measurements and is used by one Dutch contractor. The iScan is intended for mounting on an implement and does not measure pH. After scanning, the raw data is reviewed and at least four soil samples are taken per plot. “We send the soil sample results to Veris to calibrate the raw data. The calibrated data is qualified and delivered to the client.” data.”
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‘pH is a consequence’
Under the name SoilMasters, FleurenTech, Healthy Soil, and Van den Borne Potatoes have been collaborating since 2020 in the field of soil scans, analysis, and advice. They use, among others, the EM38 and Dualem21hs soil scanners, which measure soil conductivity (EC) contactlessly via electromagnetic induction. “This is done using a sled pulled by a quad, for example,” says Marco van Gurp of Healthy Soil. “Currently, the Dualem21hs is our most-used scanner. It measures conductivity to a depth of 3 meters, but we use the 0 to 50 cm layer.”
If your soil is in order, organic matter, pH and nutrients will follow
Immediately after scanning, the data is analysed, and the scanned area is divided into 4 zones based on EC values. A soil sample is taken in each zone for validation. For (a group of) plots up to 25 hectares, 4 soil samples suffice. The samples are analyzed in the United States according to the Albrecht method, processed into soil reports, and then into a recommendation. “EC values correlate nicely with the parameters from the Albrecht analysis and thereby give value to the scanned zones and variation within a plot. You get something like a blueprint of the soil house, as we call it. We can also derive organic matter percentage and pH from the scans, but both are really a result of the landowner’s management. The same goes for nutrient availability such as N, P and K. If your soil house is in order, organic matter, pH and nutrient levels will follow,” Van Gurp emphasises.
27 data layers
In 2022, Syngenta signed an agreement with the British partner of SoilOptix to use the technology in the EU under the name Interra Scan. Aron Bom, New Farming Technology Agronomy Specialist Benelux at Syngenta, said: “With the Interra Scan, we map 27 data layers of the soil, including soil moisture, organic matter, pH, texture (clay, sand, and silt), as well as nutrients like potassium, magnesium, and the PAL value (phosphate status). If desired, we can also derive the variation in nitrogen status from the percentage of organic matter and soil texture.”
As with other providers, the measurements from the soil scanner are used to determine the location of soil samples for validation. Depending on the size of the plot, this involves four or more samples. The client receives both raw and validated data.
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Satellite data as a major step
Soil-Data (formerly BioScope) provides soil zone maps based on imagery, mainly from Sentinel satellites. “These are satellite images of arable land taken in winter or spring. The current resolution is 10 by 10 meters, and there should be no crops present on the plot. Cloud cover and cover crops make it more difficult to map soil conditions with satellite imagery, but at the same time, the state of a cover crop reflects the soil condition. By combining datasets, we can still draw sufficient conclusions about the variation in soil parameters,” says Tamme van der Wal, director of Soil-Data.
“We provide insight into the variation in organic matter and texture (clay, sand, and silt), and possibly in the variation of pH. Insight into other values and nutrients is also possible, but these are derived from the parameters mentioned. We validate the measurements with 2 soil samples per plot because without soil samples, no insight into soil parameters can be gained, not with any scanner or sensor. Measuring or scanning from closer is better, but 99% of farmers have a composite sample taken, and compared to that, satellite data is already a huge step forward.””
Goal-oriented and robotic soil analysis
Can current soil scans contribute to the government’s goal-oriented approach, as advocated by BO Akkerbouw and NAJK? Not for most soil scanners, which do not measure nutrients, and especially not nitrogen minerals (N-min). For that, more soil samples are needed—much more than the number taken to validate soil scans. Perhaps the call from High Tech NL, the industry association for the Dutch high-tech industry, for project partners to develop robotic soil analysis could lead to less time-consuming, less labor-intensive, and more efficient soil analysis.
