High output scanning for essential soil data

Article taken from the Arable Farming - February 2017, written by Geoff Ashcrost

Live scanning is more often associated with animals than fields.  But Bury St Edmunds-based Mount Liming has been live scanning stubble fields to gather an extensive level of soil data for its customers.

Greater level of data

Unlike traditional grid sampling systems, this latest development affords collection of a far greater level of data, says the company.  This includes the simultaneous measurement of organic matter (OM) using an optical sensor and it can also determine soil pH using on-board electrodes and record soil texture through electro-conductivity (EC) scanning.

And it does so on-the-go at speeds of up to 15kph, while logging all the sample data on a GPS map.  So how is this high definition data process carried out?

Data collection is achieved with a tractor-mounted implement called the MSP3 from US make Veris Technologies.  Currently, there is only one MSP3 in the UK and it is owned by Plantsystems, the technology division within Agrovista.  And field scanning has been carried out by contractor Mount Liming.

Agrovista's Lewis McKerrow says: "Simply getting an average field level of organic matter just isn't good enough as it can vary significantly across a field.  This is something which has been impossible to pick up until now, without impractical levels of lab analysis.


"By measuring several soil parameters on-the-go, we can quickly gain a massive insight into the yield drivers within a field and indeed across a farm.  This is much more clearly defined data."

Once soil measurements have been collected by Veris, they can be assessed and used to determine variable rate application maps for a wider variety of inputs, as Graeme Barrett, precision farming manager at Mount Liming, explains.

"Veris let us quickly collect a far greater level of field detail, and to a much more intense level than regular grid sampling," says Mr Barrett.

"This gives us a great insight into a field's organic matter content, its yield potential and pH levels.  From the data collected by Veris, we can overlay multiple maps to determine different variable rate application maps including seed, fertliser, lime and farmyard manures."

Organic matter (OM) is a crucial soil component when it comes to crop production, and a precise field map of how it varies will be invaluable to growers, Mr Barrett adds.  Such a map could also influence future cropping decisions and the adoption of cover crops to improve organic matter levels.

"OM forms slowly over time, and it influences soil texture and internal drainage.  And increased OM levels will lead to better water holding capability in the long run."

While the implement does not scan every square centimetre of a field, it samples and monitors soil based on tramline widths.  Veris gathers more EC and OM readings than pH, though it still collects about 12-25 pH readings per hectare.

Spacing equivalent

"We have set Veris to run at spacing equivalent of half the customer's tramline width,"  Mr Barrett says.  "So a 24-metre tramline system will see Veris sampling at 12m widths.  We run just off the tramline positions to avoid any influence from compaction, and then we'll run every other bout across the field, then come back across the field between them.

"This rules out any machine variations and evens out the data gathering process.

"And because Veris works on much more of the total field area than traditional grid measurements, it does reveal many more pockets of variation," he says.  "This leads to more precise mapping, which also delivers more clearly defined areas for subsequent treatments."

Mr Barrett adds there are additional benefits from using the technology.

"Overlaying maps also lets us create many different zones and that has led us towards understanding a field's water holding capacity," he says.  "We can then take deep core samples from areas known to have recorded high, medium and low values, to ground truth with what we've found.  This has given us the capability to deliver variable rate irrigation maps for vegetable growers.  It is very expensive to over-water heavier parts of the field, just to saturate lighter, sandy areas."

Mr Barrett says data from Veris has also made it much esier to pinpoint areas in fields which are particularly vulnerable to leaching.

"Customers can benefit from more precise management techniques given the accuracy and intensity of the field data which Veris can record.

Grid sampling, by comparison, is a much slower process and remains one which needs a lot of assumptions to average out data to build a field image.  It also relies heavily on computer generation to fill in the blacks between samples, leading to extensive averaging, though it does provide nutrient data for P, K and Mg levels in addition to pH data, he says.

Veris delivers multiple layers of data and, at a cost of about £30/ha, appears to offer a much more cost-effecitve process of data collection.

"If you're paying £20/ha for grid sampling, Veris delivers three distinct layers of data for just 50% more cost, with the option to define zones where you can then target nutrient analysis more accurately.

"You do get a much more crisp field map from having a greater number of sample points in the same field and it's a one-off operation, so no repeat sampling."

Since starting the process in summer 2015, Mount Liming has so far covered about 800ha.

Logistical challenges

Andrew Mount, of Mount Liming, says: "We do face some logical challenges.  While output of the system is good, we have been transporting it to and from farms on a trailer, behind a 4x4."

While its existing lime application business sees the firm covering 10 counties in the east of England, the introduction of Veris sees the firm travelling as far south as Kent and Southampton, across to Shropshire and up to Yorkshire.

"It is quicker and easier to move the unit on a trailer and arrange to use a customer's tractor with Veris," he says.  "While the unit is pretty versatile, we've seen both ends of the spectrum from full auto-steering guidance to a 30-year-old tractor without electronics.  It makes things a little trickier to drive to a GPS-controlled field pattern to suit the MSP3's sampling process - but it's not impossible.

"Soil types never really change, where OM and pH values do shift, depending on your treatment plans," says Mr Mount.  "Data from Veris will then enable you to carry out much more precise targeting when sampling in future, instead of working to a grid."


What is the MSP3?

The Veris MSP3 (Mobile Sensor Platform, three elements) is essentially a soil lab on wheels which can determine soil texture, pH and organic matter content as it trundles acorss a field at speeds of up to 15kph.

Developed by US firm Veris Technologies, the linkage-mounted implement is just 2.3m wide.  Up front is a series of transmitting and receiving discs which run in the soil and are used to measure electrical conductivity.

The steel discs afford conductivity measurement at two depths - the first is to a depth of 0.5m to determine data for nutrient mapping and availability; the second is to a depth of 1m - and provides data for variable rate seed maps.

The centre of the machine plays host to a near infrared (NIR) optical sensor.  This device is used to measure organic matter through reading soil colour.  A set of discs run ahead of the sensor to clear away surface trash, while a pair of discs follow, and also conceal the sensor.

Shallow slot

These discs prepare a shallow slot into which sensor is pushed.  Isolated from light, conditions are ideal for th eNIR unit to determine soil colour.  Lighter coloured soils have a high reflectance, while darker coloured soils have a lower reflectance and absorb more light.

The final element is a pH measurement unit.  This automatic device uses a steel shoe which is pushed into the ground to a predetermined depth every 25m and demands the implement is pulled with some speed.

As soil flows through the unit, it is automatically hoisted out of the ground, placing the captured soil against two probes which constantly cross-reference each other's data - it is said one probe alone could lead to errors and mis-readings.

It takes about 10 seconds to gather pH data, before the shoe is lowered back into the ground to capture the next sample.  At the same time, wash justs automatically clean the probes of any soil to avoid contamination, which is what the unit carries a water tank.

Cleverly, the system Geo-references the exact spots where all readings are taken, enabling precise, high-definition map data to be generated.


31 January 2017

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