Nitrate sensor | Real-time monitoring of soil and surface water quality

The use of sensors to monitor the quality of agricultural soil and surface water is increasingly common. But the monitoring systems currently used are cumbersome. The measurements are not particularly accurate and the results are only available some time later. TNO develops optical sensors that are affordable and easy to use. They also provide very precise measurements in real time. This makes it easy to determine and monitor nitrate concentrations and their sources.

Nutrient leaching risks

Fertilisers enrich soil with nutrients such as phosphate and nitrate. These minerals are essential for crop growth. But in excess they cause problems, leaching into ground and surface water and potentially affecting the quality of our drinking water. If fertiliser concentrations are likely to exceed threshold levels, stakeholders such as water authorities, provinces and water treatment plants need to know as soon as possible.

Prototype tested

TNO’s prototype nitrate sensor was developed in close collaboration with Wageningen University & Research (WUR) and several agricultural companies. This made it possible to combine in-depth knowledge of technology, farming, water management and enterprise. The initial test on farmland was successful. The nitrate sensor was developed to help farmers monitor soil conditions and make very precise adjustments to fertiliser application as part of precision agriculture. Now we want to partner with companies interested developing the sensor for different types of soil and surface water.

Expansion of the existing monitoring network

In the early 1990s a national monitoring network known as the Dutch Minerals Policy Monitoring Programme LMM was established to monitor the effects of the manure and fertiliser policy adopted in the Netherlands. Several hundred farms are taking part. WUR and the National Institute for Public Health and the Environment (RIVM) gather the data and monitor water quality.

If the sensor developed by TNO can be marketed at an acceptable price, it will enable massive expansion of the monitoring network and provide real-time data that makes it easier to control mineral concentrations at source. Data no longer has to be sent to a lab for analysis. Optical measurements are constantly fed into a national system in real time and enable faster and more efficient soil and water management measures.

Optical measurement

The fibre-optic sensor uses light to measure nitrate concentrations in water and soil. We have concrete plans to expand the potential applications of the sensor, including adaptation for use with other substances such as ammonium, in the foreseeable future. Once this has been achieved, it will be possible to implement larger scale monitoring that assesses factors such as nitrogen deposition in Natura 2000 nature protection areas. Mass transition to optical measurement will enable faster and more effective measures to ensure fertile soil and healthy drinking water. It will also facilitate optimal use of fertilisers in farming, improving crop growth and conserving resources.

TNO is keen to talk to companies interested in further developing the sensor, adapting it for use with other substances and bringing it to market.