A new soil-testing service based on US technology will allow growers to measure differences in organic matter across their fields.

The service offered by the Plantsystems arm of Agrovista uses the MSP3 machine developed by US firm Veris Technologies to measure and map pH, electro-conductivity and organic matter in a single pass.

It gives growers and their agronomists the ability to map differences in soil health across a field, highlighting areas that need attention.

The decline in soil organic matter levels in UK arable rotations has been well documented in recent years. Low levels are associated with poorer soil health and crop yields.

See also: Strip-till innovation doubles soil organic matter

Consequently many farms have been putting in measures such as cover crops to help turn things around, says Lewis McKerrow, head of precision technology with Agrovista.

“One of the difficulties that farmers have faced with this task is that organic matter levels can vary significantly across a field,” he adds.

“Up until now, it has been impossible to quantify this variation without having to resort to impractical levels of laboratory analysis.”

Other measures

As well as measuring the three components considered to be the key yield drivers, either within a field or across a whole block, the system can also be used to produce detailed zones of nitrogen leaching and water-holding capacity.

“One of the main features of this machine is that it collects all this data as it is towed along behind a tractor,” Mr McKerrow explains.

“The whole job is very quick – the machine is pulled at up to 16km/hour, typically in 12m widths, so a huge amount of data is captured in one day and in one operation.”

With the MSP3, electro-conductivity and organic matter readings are measured constantly, while the pH is read about 15 times per hectare via a shoe that is lowered into the soil.

At the end of each field, a number of locations are selected where pH, electro-conductivity and organic matter readings are among the lowest and the highest. These areas are then sampled by hand and sent to a laboratory.

This ground-truthing gives an accurate calibration of the data, which means it can be interpreted and analysed with great precision, Mr McKerrow says.

“From there, you have the data you need for variable-rate applications and management decisions, such as where to target inputs of organic manures and cover crops.”

While there is a strong correlation between organic matter and yield, other soil parameters can be just as significant, he adds.

“Soil variations highlighted by electro-conductivity maps are often very close to where the yield variations occur.”

The cost of the new service will be £25/ha.

How does the machine work?

• Organic matter – a sensor uses the colour of the soil to create a map of organic matter, which is then calibrated with samples taken by hand from the field.
• Electro-conductivity – discs create a circuit in the soil from one end of the machine to the other. The resistance is measured, in order to determine the soil type. The wider apart the discs, the deeper the conductivity map will be. These maps form the basis for nutrient and seed rate decisions.
• pH – a funnel-like sensor is pushed into the soil every 7-10 seconds, which channels the soil through it as the machine is moving. This is lifted out and cleaned before repeating the process.