Nitrate sensor: Measurement system to prevent over-fertilisation

Does a lot help a lot? – Unfortunately not. The excessive use of fertilisers has catastrophic consequences for the environment, health and the climate. However, farmers lack the means to be able to precisely determine the amount of nitrate in order to adjust the exact amount of fertiliser. Together with his team, Dr Nicolas Plumeré, electrochemist at Ruhr University Bochum, has developed a nitrate sensor which farmers will soon be able to use to determine the nitrate content of field crops themselves.

Farmers are currently using up to twice as much fertiliser as crops actually need. This introduces excess nitrate into the soil, which damages the environment. Even the production of the nitrogen fertilisers damages the climate. Each year they consume roughly one per cent of global energy demand, and approximately 250 million tonnes of CO2 are emitted in the process – after all, one third of all German emissions. Up until now, only a few methods have been available for determining the quantity of nitrate in the field and therefore calculating the amount of fertiliser required. As these processes are resource intensive and expensive, farmers rarely use them.

Engine for progress:

  • immense CO2 and energy saving potential by adjusting fertiliser quantities
  • a tricky combination of biochemistry and electrochemistry to determine the nitrate concentration
  • simple handling of the future sensor, similar to a blood glucose metre
  • NRW know-how in the area of electrochemistry is contributing to the success
  • the first prototype nitrate sensor is expected in only a few years

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© RUB, Photo: Gorczany

Dr. Nicolas Plumeré had already begun working on a nitrate sensor in the USA. However, he made the breakthrough for the application during his years of research at RUB (Ruhr-Universität Bochum). The expertise available here in the area of electrochemistry has also contributed.

Furthermore, many fields are over-fertilised by approximately 100 per cent with the excess quantity of nitrate being washed away and ending up in waters and the atmosphere. However, it is currently impossible to stop over-fertilising, as "there are no simple, manageable analytical processes available," according to Plumeré. He has therefore taken the approach of making the process of determining the amount of nitrate as simple as determining the level of blood sugar. To do so, the French chemist employs two clever tricks.

  • Trick No. 1: The nitrate content of the plant rather than that of the soil is determined. This does not depend on weather conditions and the optimum nitrate concentration is known for practically all plants. Once the farmer has determined the actual concentration, he is able to systematically reapply the fertiliser accordingly.
  • Trick No. 2: The process is made suitable for use in the field by means of a sophisticated combination of biological and electrochemical reactions in the sensor.

“The atmospheric oxygen which is impossible to avoid when using a sensor in the field normally distorts the measurement results. However, in our sensor it is simply captured by an enzyme in order to give the correct result," says Plumeré.

The research group is currently optimising the measurement process in order to make it robust enough to deal with all interferences in the field. A functional prototype could be available within one to two years, and a market-ready product within three to five years.

Photo: Gorczany

"By reducing the use of plant fertilisers to the necessary extent, we could save CO2 emissions and energy consumption to the scale of a small country"

Dr. Nicolas Plumeré, Ruhr-Universität Bochum

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