Determination of Nitrate and Nitrogen in surface water and agricultural applications
Nitrogen is a crucial nutrient that helps plants and crops grow, but high concentrations are harmful to people and nature. Pure, clean water is vital to human health and to natural ecosystems. Excess nitrogen from agricultural sources is one of the main causes of water pollution in Europe. Studies done by Wageningen University & Research in collaboration with Glastuinbouw Nederland, Acacia Water, Hoogheemraadschap Delfland, Fixeau B.V. and Stichting AKVO have proven the usability of the LAQUAtwin meter in this application.
Introduction
Nitrates and organic nitrogen compounds from fertilizer and manure enter groundwater through leaching and reach surface water through runoff from agricultural fields. A high level of nitrate makes water unsuitable as drinking water.
In rivers, lakes and marine waters, nitrogen and other nutrients, in particular phosphorus, stimulate the growth of algae. At moderate levels, algae serve as food for aquatic organisms, including fish. However, excessive nutrient concentration in water systems will cause algae to grow excessively. This affects the natural ecosystem and can lead to depletion of oxygen in the water. This phenomenon, known as eutrophication, has negative consequences for biodiversity, fisheries and recreational activities.
Both phosphorous and nitrogen play a role in eutrophication, but while the main cause of eutrophication in fresh water is phosphorus, it is mainly caused by nitrogen in marine water.
EU Directive
The maximum allowable nitrate concentration in surface water is 50mg/l (ppm) NO3- or 11,3 mg/l NO₃-N.
The EU Nitrates Directive (91/676/EEC) aims to protect water quality across Europe by preventing nitrates from agricultural sources that pollute ground and surface waters and by promoting the use of good farming practices.
The Directive aims to reduce water pollution caused by nitrates used in agriculture by
- monitoring nitrate of water bodies
- designating nitrate vulnerable zones
- establishing codes of good agricultural practices and measures to prevent and reduce water pollution from nitrates
Source: https://environment.ec.europa.eu/topics/water/nitrates_en
Method
Testing for nitrates in water can be done in the laboratory, online and in the field. The determine the source of potential nitrate pollution a field measurement is preferred.
There are several methods to measure nitrate in water in the field. These range from simple test kits to more advanced measurement equipment.
Some commonly used methods are:
Chemical Test Kits
- Based on colour change.
- Sample is mixed with reagents that convert into a coloured solution. The intensity of the colour is measured.
- Change is read using a colour scale or spectrophotometer.
- Advantages: Portable, relatively inexpensive, quick.
- Disadvantages: Less accurate
Spectrophotometry
- Measures absorption of light by the solution at specific wavelengths.
- Absorption is converted into a concentration using a calibration curve.
- Advantages: High accuracy.
- Disadvantages: Less suitable for field conditions, more expensive, less portable than other methods.
Ion-Selective Electrodes (ISE)
- Ion-selective electrodes respond specifically to nitrate, allowing a direct measurement of the concentration.
- Advantages: Fast, portable.
- Disadvantages: Requires calibration and maintenance.
Test Strips (Dipsticks)
- Dip into the water to measure.
- Colour changes based on the concentration, the colour is compared to a scale to read the concentration.
- Advantages: Very simple, fast, and inexpensive.
- Disadvantages: Less accurate and sensitive than other methods.
Portable UV-Vis Spectrometers
- Measure light absorption.
- Similar to lab-based meters but more compact and suitable for fieldwork.
- Advantages: Very accurate, suitable for detailed field measurements.
- Disadvantages: More expensive and less portable.
Each method has its own pros and cons depending on the situation, such as accuracy, cost, ease of use, and required equipment. For field measurements, simple kits or test strips are often the most practical, while ion-selective electrodes or spectrophotometry are recommended for more precise work.
Instruments
For measurement of nitrate (NO3-) and nitrate nitrogen (NO3-N) the HORIBA WQ300 series handheld and LAQUAtwin pocket meters can both be used. The HORIBA instruments use Ion Selective electrodes to measure the concentration.
In field test conditions, where both instruments were used there was a good correlation between the results of the two instruments.
Research
Recent research by Wageningen University and Research (www.wur.nl) has shown the usability of the LAQUAtwin NO3-11. WUR published the results in this report: https://research.wur.nl/en/publications/ontwikkeling-en-evaluatie-van-een-handzame-nitraatmeter-voor-drai
Citation from the abstract of the report: By 2027, greenhouse horticulture in the Netherlands must grow almost emission-free. Measuring surface water quality by growers themselves on and around their greenhouse could provide more insight into disasters. Measuring nitrates in surface water seems to be a good method to detect fertigation water in surface water due to leaks. Research has therefore been conducted into a nitrate meter that growers can easily use themselves.
Based on desired technical and practical specifications, handheld meters available on the market and prototypes from research have been assessed for, among other things, suitability, accuracy, ease of use and cost price. A practical evaluation was carried out at six greenhouse growers using the handheld meter found to be most suitable. The meter has been found to be handy, robust, and sufficiently reliable to detect increased concentrations of nitrate in surface water. The meter has a large measuring range, allowing measurements to be made in surface water as well as in nutrient solutions and drainage water.
To detect leaks, the surface water must be checked weekly. The accuracy of the meter is less than that of laboratory analyses, but the low purchase price and operational costs are such that the use of the hand meter is more economical as soon as more than one measurement is carried out per week.
Field test WQ300
In the Netherlands the WQ300, with nitrate ion sensor head and cartridge, was compared against brand “Y” in the lab and during field test by Hoogheemraadschap Delfland*.
|
HORIBA |
Brand Y |
|
|---|---|---|
|
Battery live |
400 hrs |
80 hrs |
|
Sensor technology |
digital |
analog |
|
Stores cal data when replacing batteries |
Yes |
No |
|
Field calibration |
Yes |
No |
|
Wireless data transfer |
Yes |
No |
NO₃⁻ or NO₃-N
The terms "nitrate (NO₃⁻)" and "nitrogen (NO₃-N)" both refer to forms of nitrogen, but they are used in different contexts, and there is a distinction between them:
Nitrate can be converted to nitrate nitrogen by dividing the NO - with 4,4268 and vice versa:
- 100 mg/L (ppm) NO3- = 22,58 NO₃-N mg/L (ppm) (100 / 4,4268).
- 22,58 mg/L (ppm) NO₃-N = 100 mg/L (ppm) NO3- (100 x 4,4268).
LAQUAtwin: the only meters with flat sensor technology.
HORIBA’s highly-sensitive, flat sensor technology opens up new possibilities for sampling and sample types. Only a small amount of sample is required, so you can easily sample in situ without the need for beakers or other labware. Sensors are easily replaced as required.
Calibrate and measure at the touch of a button — the smiley face will tell you when the result can be read.
LAQUAtwin is fully waterproof and dustproof.
The meter and sensor are fully waterproof* and dustproof, so you can take it anywhere.
* IP67 rated. Will withstand immersion for 30 minutes at 1 m. Not suitable for underwater use.
Carry case comes as standard for handy portability.
The compact carry case contains everything you need for your measurements, including the standard solution and sampling sheets.
Matching products
Horiba LAQUAtwin Nitrate Ion Tester NO3-11 for Precise On-Site Measurements Handheld tester with 2-point calibration, ideal for water and environmental measurements The Horiba LAQUAtwin Nitrate Ion Tester (NO3-11) is a portable device for direct determination of nitrate ions (NO3) and temperature in liquids and samples. Thanks to the ion-selective electrode and compact design, the tester delivers fast and reliable results. The integrated temperature unit enables temperature-compensated analysis and clearly displays both nitrate and temperature values on the digital LCD display. Mobile Nitrate Ion Tester for Precise On-Site Analyses The integrated temperature measurement enables temperature-compensated analysis and shows both nitrate and temperature values. Only very small sample volumes are required, minimizing sample consumption and increasing efficiency in daily use. The tester can be set up with up to two calibration points, with features such as automatic standard recognition, adjustable calibration values, and multiplication compensation for flexibility. Only minimal sample volumes are needed for each analysis, reducing sample usage and improving efficiency. Why Nitrate Measurement Is Crucial – and a Pocket Tester from Horiba Is Ideal Nitrate measurement plays a central role in agriculture, water management, and environmental monitoring. Elevated nitrate concentrations can affect drinking water quality, stress ecosystems, and contribute to over-fertilization. At the same time, nitrate is an essential nutrient for plants, and targeted control is vital for sustainable agriculture. A mobile nitrate pocket tester enables rapid on-site analysis without time-consuming laboratory tests. This allows early detection of contamination, immediate action, and reliable monitoring of legal limits. The Horiba LAQUAtwin NO3-11 combines this flexibility with high measurement accuracy and easy operation – ideal for routine checks and scientific applications. The tester can be configured with up to two calibration points. Features like automatic standard recognition, adjustable calibration values, and multiplication compensation provide high adaptability to different sample types and measurement conditions. Typical Applications of the Horiba LAQUAtwin Nitrate Ion Tester (NO3-11) Agriculture: To optimize fertilizer use, promote plant growth, and minimize environmental impact, farmers and agronomists use the tester to monitor nitrate levels in soils and irrigation water. Water Quality Management: To maintain nitrate concentrations within safe limits, the NO3-11 is used in water management to check drinking and wastewater quality. Environmental Monitoring: The NO3-11 allows environmental technicians and scientists to quickly analyze nitrate contamination in rivers, lakes, and groundwater, ensuring compliance with environmental standards and identifying pollution sources. Research and Development: The tester is used by scientists in environmental science, hydrology, and soil science to conduct detailed studies of the nitrogen cycle and the effects of nitrates on ecosystems.
The LAQUAtwin Nitrate Ion Handheld Tester (NO3-11C) included in the analysis kit is pre-set by the factory to the relevant calibration points 30PPM and 300PPM for soil analysis. Manufacturer Part No. 3200689164 | B-742
Precise Nitrate Tester for Plants – Mobile NO₃⁻ Analysis On-Site Horiba Nitrate Ion Pocket Tester Kit for fast and accurate on-site results The Horiba LAQUAtwin Nitrate Ion Hand Tester (NO3-11C) in its practical analysis kit is your mobile laboratory for reliable determination of nitrate ions and temperature in plant sap samples. With a wide measurement range of 6 to 9900 ppm NO₃⁻ and automatic temperature compensation, the device provides fast and accurate results. The ion-selective electrode ensures precise NO₃⁻ measurements, while the digital backlit display allows quick and easy reading of values. Mobile nitrate analysis kit for plants, water, and environmental monitoring The kit contains the handheld tester, five pipettes, three measuring cups, a plant sample press, standard solutions, and sampling sheets. This setup allows for rapid and reproducible analysis of plant sap without the need for additional laboratory equipment. The device is dust- and waterproof, features automatic standard recognition, Auto-Stabil and Auto-Hold functions, and has a long battery life, making it ideal for mobile use in the field, greenhouse, or laboratory. Why nitrate measurement in plants is important – and why a mobile kit is ideal Nitrate content in plants is a key indicator of nutrient supply, plant growth, and agricultural product quality. Excessively high or low nitrate levels can negatively impact yield, plant quality, and environmental compatibility. A mobile nitrate hand tester allows direct analysis of plant sap on-site, without time-consuming laboratory procedures. Fertilization and irrigation measures can be precisely adjusted, and over- or under-supply can be detected early. The Horiba LAQUAtwin NO3-11C provides a precise, fast, and practical solution for this purpose. Typical applications for the Horiba Nitrate Analysis Kit Aquaculture and coral monitoring Aquaristics Horticulture Beverage and food production Laboratories and schools Environmental monitoring Water treatment Water conditioning
Thank you for your interest in our smart and customizable Horiba WQ-300 series instruments.The high-quality digital multi-parameter handheld meters with their generous color LCD display with LED backlight (7 cm x 5.2 cm) are ideally suited for use in the field under all conditions and in direct daylight.Use our configurator to freely select the suitable measuring device of the WQ-300 Horiba series (1 to 3 channels), the measuring parameters (sensor cartridges) and desired cable length (with integrated sensor receptacle + digital module) according to your wishes and requirements. At a later stage, you can always connect another available measurement parameter to the device via the corresponding sensor cable or carry it in the case as a supplement. As with other handheld measuring devices from Horiba, a major advantage of these devices is that the measuring devices are highly resistant to shock, slipping and scratching thanks to a special rubber coating. Only four standard AA 2500 mAh batteries are required for operation, and to give you more flexibility when you are on the move, the WQ-300 series devices can also be powered by a powerbank or battery pack via the integrated USB interface. The IP67 certification, which certifies dustproofness and protection against temporary submersion for up to 30 minutes at a water depth of one meter, completes the overall professional package, along with the usual ergonomic design and ease of user operation. Horiba attests to its outstanding product quality by offering a three-year warranty on the LAQUA WQ-300 series handheld meters. Other added values and features:During analyses, the user is supported by the display of operating instructions in the form of smiley icons, which is supplemented by an LED status display on the sensor. This is intended to prevent operating errors, which can lead to implausible measurement results. The design decision to install only a small number of control buttons and not to implement any nested user menus serves to ensure that the devices can be operated easily and safely even during discontinuous use as well as when used by other users. The measuring instruments have an electrode wear indicator, a measuring stability indicator on the instrument and sensor, a locking function to "save" the currently measured value on the display, free naming of the measuring point (8 characters), automatic calibration functions, integrated sensor holders, self-diagnosis function, as well as GLP functions. The fold-out stand on the back of the instruments means that you always have your hands free to carry out your measurements easily and safely. Measurement data can be conveniently transferred to your computer or cell phone via USB or WiFi.All handheld meters of the 300 series are delivered in a reinforced measuring case for mobile use in the open air. This provides space for the meter, for electrodes and cables, for up to eight 60 ml bottles of buffer solutions including an integrated buffer solution bottle holder for easier calibration. Particularly noteworthy is the automatic sensor recognition of the instrument through the use of sensor cables with integrated digital sensor recording. Information about the sensor, calibration data as well as measurement settings are stored in the sensor recording and transmitted to the measuring instrument. In addition, calibration of all connected sensors is possible at the same time, since each sensor head independently stores the measurement and calibration data and transmits it to the WQ300 series measuring device.Optionally, there is the possibility to connect and use analog sensors via the Horiba BNC sensor adapter with the device, please contact us for this.Languages:GermanEnglishFrenchSpanishPortugueseChineseScope of delivery:WQ-300 series handheld meter in a carrying casethe digital electrode you have chosen, if applicable, and the corresponding sensor-specific cable with integrated digital sensor receptaclemanualManufacturer article number single measuring device WQ-310-K 1 channel: 3200832605 Note: Chloride sensor, if selected, is supplied without chloride ion strength regulator and chloride electrode filling solution. This must be procured by the customer. Without the filling solution the sensor can´t be used. Why We Use These Measuring Devices in Water Treatment Precise calcium control is a key element of efficient water treatment – from drinking water purification and process water management to environmental analysis. Elevated calcium levels can lead to scaling, pipe damage, energy losses, and disruptions in chemical processes. For this purpose, we offer tailored high-end solutions from the Horiba LAQUA WQ Series (WQ310-K, WQ320-K, WQ330-K) in our online shop, specifically designed to meet the needs of water technology: WQ310-K: Single-parameter solution for targeted measurements • WQ320-K: Simultaneous monitoring of, for example, calcium and conductivity • WQ330-K: Three-channel measurement for complex real-time multi-parameter analyses Why We Rely on These Devices: • They provide reliable data for controlling and optimizing water treatment systems • They offer digital evaluation, documented results, and interfaces for process integration • They are robust, packaged in a practical analysis case, and thus also suitable for mobile on-site use • They allow calcium to be measured in combination with other parameters such as pH, conductivity, or redox – for a holistic and efficient approach
Thank you for your interest in our smart and customizable Horiba WQ-300 series instruments.The high-quality digital multi-parameter handheld meters with their generous color LCD display with LED backlight (7 cm x 5.2 cm) are ideally suited for use in the field under all conditions and in direct daylight.Use our configurator to freely select the suitable measuring device of the WQ-300 Horiba series (1 to 3 channels), the measuring parameters (sensor cartridges) and desired cable length (with integrated sensor receptacle + digital module) according to your wishes and requirements. At a later stage, you can always connect another available measurement parameter to the device via the corresponding sensor cable or carry it in the case as a supplement. As with other handheld measuring devices from Horiba, a major advantage of these devices is that the measuring devices are highly resistant to shock, slipping and scratching thanks to a special rubber coating. Only four standard AA 2500 mAh batteries are required for operation, and to give you more flexibility when you are on the move, the WQ-300 series devices can also be powered by a powerbank or battery pack via the integrated USB interface. The IP67 certification, which certifies dustproofness and protection against temporary submersion for up to 30 minutes at a water depth of one meter, completes the overall professional package, along with the usual ergonomic design and ease of user operation. Horiba attests to its outstanding product quality by offering a three-year warranty on the LAQUA WQ-300 series handheld meters. Other added values and features:During analyses, the user is supported by the display of operating instructions in the form of smiley icons, which is supplemented by an LED status display on the sensor. This is intended to prevent operating errors, which can lead to implausible measurement results. The design decision to install only a small number of control buttons and not to implement any nested user menus serves to ensure that the devices can be operated easily and safely even during discontinuous use as well as when used by other users. The measuring instruments have an electrode wear indicator, a measuring stability indicator on the instrument and sensor, a locking function to "save" the currently measured value on the display, free naming of the measuring point (8 characters), automatic calibration functions, integrated sensor holders, self-diagnosis function, as well as GLP functions. The fold-out stand on the back of the instruments means that you always have your hands free to carry out your measurements easily and safely. Measurement data can be conveniently transferred to your computer or cell phone via USB or WiFi.All handheld meters of the 300 series are delivered in a reinforced measuring case for mobile use in the open air. This provides space for the meter, for electrodes and cables, for up to eight 60 ml bottles of buffer solutions including an integrated buffer solution bottle holder for easier calibration. Particularly noteworthy is the automatic sensor recognition of the instrument through the use of sensor cables with integrated digital sensor recording. Information about the sensor, calibration data as well as measurement settings are stored in the sensor recording and transmitted to the measuring instrument. In addition, calibration of all connected sensors is possible at the same time, since each sensor head independently stores the measurement and calibration data and transmits it to the WQ300 series measuring device.Optionally, there is the possibility to connect and use analog sensors via the Horiba BNC sensor adapter with the device, please contact us for this.Languages:GermanEnglishFrenchSpanishPortugueseChineseScope of delivery:WQ-300 series handheld meter in a carrying casethe digital electrode you have chosen, if applicable, and the corresponding sensor-specific cable with integrated digital sensor receptaclemanualManufacturer article number single measuring device WQ-320-K 2 channel: 3200832606 Note: Chloride sensor, if selected, is supplied without chloride ion strength regulator and chloride electrode filling solution. This must be procured by the customer. Without the filling solution the sensor can´t be used.
Horiba WQ330-K – Your Professional 3-Channel Water Quality Meter Expandable multi-parameter system for simultaneous measurement of pH, conductivity, redox, and other water parameters The Horiba LAQUA WQ330-K is a powerful multi-channel device for advanced water analysis, both on-site and in the laboratory. With three freely configurable measurement channels, it can simultaneously record parameters such as pH, conductivity, redox potential, TDS, temperature, oxygen, ammonia, calcium, chloride, nitrate, fluoride, and potassium. Intuitive operation, automatic sensor recognition, and digital calibration ensure accurate, fast, and reproducible measurements. Flexible Multi-Parameter System for Field and Laboratory Applications The analysis kit with the Horiba WQ330-K is ideal for environmental and water body monitoring, research and teaching, as well as drinking and process water control. The large LCD display with LED backlight ensures excellent readability even in direct sunlight. Measurement data can be exported and documented via USB or wirelessly, greatly simplifying traceability and analysis. The modular system allows the device to be quickly and precisely adapted to any measurement task. It is ideal for users who need to efficiently and reliably monitor multiple water parameters. Technical Features and Key Advantages of the WQ330-K The three measurement channels of the Horiba WQ330-K enable simultaneous recording of different water parameters, reducing measurement time and allowing better evaluation of relationships between parameters. The modular sensor concept allows flexible use of digital sensors, which are automatically recognized and store their calibration history. Notably, the combination of high measurement precision, user-friendliness, and mobility makes this device stand out. Quick deployment without complicated setup, along with easy data transfer for documentation and analysis, makes the Horiba LAQUA WQ330-K an ideal solution for professional water analytics.
Mobile Analysis Laboratory for Ion Measurements – Versatile Use Compact kit for simultaneous determination of multiple water and environmental parameters The Horiba 4M LAQUAtwin Kit is a mobile laboratory that allows you to determine important ion parameters directly on-site. The case contains pocket testers for measuring sodium, potassium, nitrate, and calcium, as well as for temperature measurement. Each device uses ion-selective electrodes for targeted analysis of small samples and provides fast, reliable results. In addition to the four measurement devices, the kit includes calibration solutions and a wash/spray bottle for sensor cleaning. The sensors can be stored dry without special storage solutions. Compact Multi-Parameter Kit for Flexible On-Site Analyses The set is designed for measurement tasks where multiple ions need to be detected simultaneously, for example when monitoring drinking and process water, performing environmental checks of water bodies, conducting aquaculture analyses, or agricultural research. Thanks to the case, all essential testers including accessories are always on hand and ready for immediate use. The measurement results are available in a short time and are reliable and reproducible – ideal for routine and control measurements in the field. All components are neatly arranged in the case and ready for use at any time. An additional advantage is that the sensors can be stored dry without special storage solutions. Due to its compact design, the kit is particularly suitable for mobile applications where multiple ion parameters need to be determined quickly one after the other or in parallel. Why Multi-Parameter Ion Measurements Are Useful – and a Mobile Kit Is Ideal In many applications, not just a single measurement is important, but the interaction of multiple ion parameters. Sodium, potassium, nitrate, and calcium together influence water quality, biological processes, plant growth, and technical operations. Single measurements in a laboratory are often time-consuming and inflexible. A mobile analysis kit allows simultaneous detection of multiple parameters directly on-site. This allows relationships to be recognized more quickly, decisions to be made more reliably, and measurement campaigns to be carried out more efficiently. The Horiba 4M LAQUAtwin Kit combines these advantages in a compact, user-friendly system.