New machine acts as soil lab on wheels

SPRINGFIELD, Ill.. — The new Veris MSP3 simultaneously measures electrical conductivity, soil pH and organic matter while logging the data on a GPS map.

It does all this on the go at six m.p.h.

Dubbed by some as a soil lab on wheels, the MSP3 had its first public showing at the InfoAg precision farming workshop in Springfield last month.

Veris representative Paul Drummond said advances in soil analysis technology have allowed the company to turn its original single purpose EC cart into a micro, multitasking mobile soil lab.

“We’ve blended three distinctly different technologies into one field unit,” said Drummond.

The new model is an extension of the electrical conductivity (EC) mapping machine Veris has sold to agronomists and researchers since 1997.

“MSP stands for mobile sensor platform. When we designed the original cart, the idea was that we’d gradually add more sensors as technology evolved.

“The coulters still measure EC on the go, but we’ve added on-the-go soil pH and organic matter (OM). As you travel across the field, the system geo-references the exact spots where all three readings are taken.”

Drummond said data from all three sources can be blended later into a map that provides a highly accurate picture of the field, thus allowing more precise management.

However, in most cases the pH map is a standalone used strictly to make lime recommendations in regions where that is a normal practice.

Most MSP operators travel at five to six m.p.h., but Veris says accurate measurements can be taken at speeds as high as 12 m.p.h. for EC and OM mapping. Mapping for pH must be done at five to six m.p.h. so core material doesn’t fly out the back of the machine.

Drummond said the massive quantity of data collection points produce a crisper field map than a four or 2.5 acre grid system.

“With typical 2.5 acre grid sampling, cores are pulled once every 330 feet and software fills in the gaps with what it thinks should be there,” he said.

“But university studies in Iowa show that pH within a 2.5 acre grid can vary as much as it does across the entire field.”

Soil pH

According to the Iowa study reported in theAgronomy Journal,soil pH varied from 5.4 to eight over 480 feet in most transects.

“In some sections, soil pH varied about two pH units over a 40 foot distance,” it said.

The Veris Soil Manager takes 10 seconds from the time a core is pulled until it provides a pH reading. The MSP operator continues to drive the GPS controlled field pattern while this is happening.

“Soil Manager first came to the market in 2003 as an on-the-go sampler mounted to the MSP,” Drummond said. “It has only one moving component.”

The parallel linkage is hooked to a hydraulic cylinder. The controller automatically sends a message to the cylinder, which pushes the sampler shoe down into the soil to a predetermined depth. The core is delivered to the analysis instrument through a two-inch tube.

The sample comes up and pushes against two ion selective electrodes, but they don’t determine pH directly,” he said.

“What they do is measure hydrogen ions in the soil. By knowing the hydrogen ion level, we extrapolate soil pH. That’s because pH is really nothing more than a measure of the presence of hydrogen. All this is taking place in the field, on the Mobile Sensor Platform, while you’re driving the field.”

The water tank mounted to the MSP3 is necessary because high-pressure nozzles must wash all residual soil off the electrodes before the next core arrives.

More EC and OM readings are collected than pH readings, but Drummond said the system still collects eight to 10 pH samples per acre.

“That’s far better than the one pH reading every 2.5 or four acres you get with a conventional grid system.”

He said pH readings are geo-referenced to the spot where the core was pulled rather than the spot where the chemical analysis was completed.

“The pH Soil Manager is designed so consultants can do a better job of capturing the true pH variability in the field. It’s geared more toward areas of low PH,” he said.

“But at the same time, even in areas of typically high pH, there can be some low pH areas, and vice versa. Certainly the last thing anyone wants to do is to apply lime in high pH areas of the field. The Soil Manager can help avoid this.”

Organic matter

Drummond said the OpticMapper, which measures organic matter on the go, is the latest innovation from Veris.

The concept behind OM on the go is similar to normalized difference vegetation index (NDVI) imagery taken from satellites, except OM images comes from within the Earth instead of from above. It’s based on the fact that soil colour correlates with organic matter.

The ability to measure light absorption and light reflectance is the key, whether the operator is measuring vegetative density or soil structure.

The instrument uses visual (VIS) and near infrared (NIR) reflectance. The data is then processed by a spectrophotometer developed by Veris to convert soil reflectance into a value that is logged on the field map. Veris says spectrometers are used in milling, rating forages, meat processing and other food related processes.

“Soil with strong CH (carbon-hydrogen), NH (nitrogen-hydrogen) and OH (oxygen-hydrogen) bonds absorb more light, which is why wet soil and soil with high organic matter looks darker, even to the naked eye,” says Veris’ website. “ And VIS-NIR spectral data is more powerful than the human eye.”

Drummond said it’s merely a matter of mounting a module beneath the surface, facing down, and pulling it through the soil like a hoe type opener at six m.p.h.

Just as NDVI images tell us about vegetative variability on the surface, the subterranean images can be extrapolated to give an accurate reading on organic matter in the soil.

Veris puts the OpticMapper where the opener would normally mount on a single row corn planter. It’s a parallel linkage unit that provides accurate depth control and uses the regular coulters and trash managers to remove surface residue.

Drummond said consistent depth is critical to avoid incorrect readings caused by soil moisture. Also, the OpticMapper needs to run deep enough that the light sensor isn’t affected by sunlight. It must be like a photo darkroom.

The optic module is mounted in a steel plate that travels as deep as three inches underground. The light points straight down.

The unit also has a sapphire window to protect the optics as it is dragged through the soil.

Veris shines two different wavelengths through the window into the soil mass: VIS and NIR. The optic sensor measures the reflectance of the light and sends the data back to the console.

The percentage of light absorption has now been logged at specific spots throughout the field.

“We know that lighter coloured soils have high reflectance. They don’t absorb much light. These are the sandier and lighter soils with lower organic matter content,” Drummond said.

“And the darker coloured soils have low reflectance. They absorb more light. These are the soils with higher organic content. We go to the geo-referenced points with the highest reflectance and pull cores for the lab. Then go to the geo-referenced point with the least reflectance and pull cores.”

When the results come back from the soil lab, the operator assigns the correct OM designations to the two extremes and all grades of variability in between.

Correlations to the lab results are extremely high. If the lab says the highest OM is four percent and the data shows this reading at 100 points on the field, then the MSP3 operator assigns that four percent value to those specific points.

At the other extreme, if the lab says the 100 points with the lowest reading have only two percent OM, then those points are assigned a two percent OM. All the other readings fall into place between the two extremes.

Drummond said the triple tasking machine accomplishes two things for agronomists and their customers: it reduces the number of samples that must be sent to the soil lab, which saves time and money, and it provides more data collection points in the field.

“You get what we call dense data. The whole field is blanketed with data collection points, so your maps have better accuracy.”

Many Veris clients also add RTK topography mapping by installing an add-on RTK console that can be programmed to take elevation readings at the points where other readings are recorded.

That means one trip across the field can create four layers of data, creating an attractive package for producers who are serious in their precision farming endeavors.

The fully equipped MSP3 with EC, pH and OM carries a list price of $34,000 US. The unit that most prairie agronomists buy eliminates the Soil Manager pH sensor, which lowers the price to $24,700. All prices are f.o.b. Salina, Kansas, at the Veris factory. 

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