You need to measure Nitrates? There are options!

25th January 2022

Nitrogen is an essential food for plant growth.  In order to get that Nitrogen, plants will assimilate it in a large way in the form of Nitrates. Those three atoms of Oxygen and one atom of Nitrogen produce some undesirable characteristics:

• They leach easily and this means that they are highly mobile.
  • Top dressing of extensive and intensive crops, often received in the form of Ammonium, Potassium or Calcium Nitrate is effective but because of the mobility of the Nitrates compound they quickly leach to depth beyond root depth and they are therefore “lost” to the uptake by the plant. At this point they become a nuisance.
  • Sooner or later Nitrates will end up in water courses, be it streams or rivulets and ultimately therefore into rivers.
  • In the absence of streams or surface water it is also highly likely that Nitrates will find their way into groundwater.
  • Think also of industrial effluents and effects from farm manure. Nitrification will invariably fill the world with undesirable excesses of Nitrates.

• High levels of Nitrates are bad for the environment, our ecology and for humans. They have all manner of negatives. These are well documented and fall well outside the scope of this brief blog.

So how can we measure Nitrates?

• The classical way: Take a (water) sample and have your lab analyse it for Nitrates.
• If you need to record data over time then you have a couple of options
  • Use a water quality probe which has a Nitrate Ion Selective Electrode (ISE). But be careful as these devices are made for laboratory use and their life and stability on site is limited to very short term deployment. Mostly less than a week. A research paper from New Zealand has described the system as mostly unusable for field use.
  • NEW: The Hydrometrics Nitrate Sensor measures Nitrates up to 50 mg/l. (Details here: https://www.vanwalt.com/equipment/nitrate-groundwater-sensor/). It has great stability and reliability and in combination with our DataHub telemetric system can give you a continuous stream of data to your desktop.

• Don’t forget the option of measuring Nitrates by extracting water from the soil pores. This gives you great data on what is actually present at a specific horizon. Our macro-Rhizon samplers are perfect for this application. (see training session video: https://www.vanwalt.com/videos/understanding-soil-solution-sampling/ (warning: very long).

So you have options. Talk to us about your application and we can help you decide which way suits your requirements best.

Vincent van Walt

Surrey, January 2022