Portable sensor tech offers in-soil analysis

Stenon co-founders Niels Grabbert and Dominic Roth have raised more than €25m to market their invention.

The handheld Stenon FarmLab device has a battery life of more than eight hours and can be charged via a USB-C port. It includes a GPS module for identifying the location of each soil test. Picture: Stenon

On more and more farms worldwide, a portable sensor is used to quickly determine how much nitrogen fertiliser a field needs before a new crop is planted.

Soil sampling and analysis are widely carried out on Irish farms, but they only tell how much nutrients such as lime, phosphorous, and potassium are needed.

Up to now, because there is no useful laboratory test for nitrogen in soils, advice to farmers on how much nitrogen fertiliser to use has depended mainly on the previous land use, type of soil, farming system, and stocking rate. The previous applications of chemical and organic manures, the requirement of the crop, and the likely crop yield, can also be taken into account.

That has changed with advances such as the invention in Germany of the Stenon FarmLab sensor device for "in-situ" soil analysis.

Farmers can simply stick the device's probe with its various optical and electrical sensors into the soil. The probe's soil data is transmitted through the internet, where software on the system's own cloud servers evaluates the data and presents the results in a practical and easy-to-understand way to the farmer in a web app, all within minutes.

The handheld device has a battery life of more than eight hours and can be charged via a USB-C port. It includes a GPS module for identifying the location of each soil test.

The soil test results can be retrieved to a specific user account by logging in with a smartphone, tablet, or PC. The results are presented on a GPS map.

As a first step, the Stenon FarmLab user calibrates the device. The probe part is then inserted into the soil by stepping on it in much the same way as a soil sampler is used. Measuring is then triggered by tapping on the touchscreen of the control unit. After each measurement, it is necessary to clean the probe.

The Stenon FarmLab has been approved for measuring nitrogen in the soil by the German Agricultural Society, whose quality tests of foods, agricultural equipment and farm inputs are highly acclaimed around the world.

The society said the device fulfilled the prediction accuracy requirements for measuring both nitrogen content and soil moisture.

German Agricultural Society tests were carried out in 40 different fields chosen to represent the widest possible range of soil and crop situations.

The testers intentionally committed a number of operator errors to test the accuracy of the meter’s error and troubleshooting prompts. They found that the device detected operator errors and issued appropriate warnings and instructions.

They said the Stenon FarmLab is suitable for use in sandy, silty and loamy soils. They compared the device's results with laboratory analyses by five laboratories.

Stenon, co-founded by Niels Grabbert and Dominic Roth, has raised more than €25 million to market their invention.

They emphasise the potential advantages such as saving on nitrogen fertiliser use (saving up to 20% of costs), optimal crop yields after applying the right rate of fertiliser in the right time and place, and no time wasted waiting for laboratory results, with results sent to the user within seconds.

One German customer, Clemens Coenen, farms more than 600ha, growing vegetables, including 200ha of potatoes for chipping. He took part in Stenon’s research program, and learned there was enough plant-available nitrogen in the soil to allow him cut his usual nitrogen fertiliser by 50k/ha, while achieving the same yield as before. He saved at least 25% on fertiliser costs.

In Germany, necessity has been the mother of invention, because the country's relatively new fertiliser ordinance requires, among other things, a determination of the amounts of nitrogen available in the soil, at least annually, before applying significant amounts of nutrients. A device such as the Stenon FarmLab is ideal for this.

Germany now has a nationwide regulated and binding scheme for determining fertilisation requirements for nitrogen on arable land and grassland. With the Stenon FarmLab, farmers can immediately detect nutrient deficiencies or surpluses and ensure the optimum supply of nutrients to crops. Only those who know and document the nutrient status of their soil have the decisive information for fertiliser selection, and the certainty that they will not stumble over one of the many new cross-compliance pitfalls.

The nitrogen clampdown in Germany follows debate over the last decade about excessive nitrate levels in German groundwater. Nitrate content has exceeded the EU threshold rate of 50 mg/litre at 18% of verified groundwater measuring points reported to the European environment agency (28% of measuring points where agriculture is most intensive).

In 2013, the European Commission sent its first letter of formal notice to reduce nitrates in groundwater to Berlin. As Germany’s reaction was not sufficient, Brussels took the complaint to the European Court of Justice.

Eventually, the German government was given eight weeks to propose appropriate measures, or another ECJ judgment could result in fines as high as €850,000 a day.

The government agreed to tighten fertiliser regulations, with farmers in particularly polluted areas ordered to spread 20% less liquid manure.

With a nitrogen surplus (fertiliser applied in excess of what crops need) of 92kg/ha/year on German land, there has been about 1.5m tonnes of nitrogen entering the atmosphere and water in Germany. This is linked to inordinate eutrophication and algal bloom in the North Sea and Baltic Sea.

The federal government made nitrogen one of the targets of its sustainability strategy, with a target to reduce the nitrogen surplus to below 70kg by 2030.

For several hundred German farmers, the Stenon FarmLab makes the adjustment to the nitrogen clampdown easier. They can use it to measure soil temperature, moisture, and pH, as well as nutrient content. 

“Soil data is a critical piece to drive better decisions, driving up productivity while working sustainably,” said Dominic Roth.

But Stenon's ambitions with their device extend far beyond Germany, and they announced a major international breakthrough last September.

Their strategic partnership with Lavoro Agro will see the Stenon FarmLab used on 100,000 acres in the coming maize growing season across the Brazilian state of Parana. Lavoro Agro is the first Latin American agricultural inputs retailer to be listed on the Nasdaq Stock Market.

Also last year, Stenon Gmbh and Eurasia Group AG partnered to promote digitalisation in agriculture in Kazakhstan, offering farming businesses in central Asian countries the device's instant access to soil data for optimising fertiliser input.

Stenon will launch in the UK and California this year.