How can I connect the N-Tester BT to the Atfarm mobile app and measure with it?

Once you have installed our Atfarm mobile app on your mobile device and added your farms and fields to your Atfarm account, you can start analysing your crops with the N-Tester BT.


Read here what is required to use the N-Tester.



Follow these steps to connect your N-Tester BT and measure with it:



1) Install the app


If you have not already, download and install our free Atfarm mobile app from Google Play Store or Apple App Store on your mobile device. Scan the QR-Code below with your camera and follow the link, or search for Atfarm in the app store.


Install from Google Play Store:


Install from Apple App Store:




2) Prepare the analysis in the app


  1. Open the Atfarm mobile app and log in to your Atfarm account with email and password.
  2. Create or select your farm.
  3. Create or select your field.
  4. The field page opens. Scroll down to the N-Tester options and select START MEASUREMENT.
  5. Appears only the first time: Select your N-Tester model. You can manage your devices later in the settings page.
  6. Fill out the crop data sheet. The inputs vary based on country and region. Our nitrogen recommendations are only valid for certain crops and development stages. The app provides you this information in the crop data sheet.
  7. Click START MEASURING and allow the app to track your GPS position. Read here why we ask for your location.



3) Connect your N-Tester BT


Our N-Tester BT is connected via Bluetooth® wireless technology to the Atfarm mobile app. The Bluetooth® wireless connection is not enabled by connecting the device in the Bluetooth® wireless technology settings of the operating system (Android, iOS) as usually known from other devices. Our Atfarm mobile app automatically establishes a temporary connection in the background.


Proceed as follows to connect your N-Tester BT:


  1. Turn on Bluetooth® wireless technology on your mobile device.
  2. Hold down the ON/OFF button of your N-Tester BT for a few seconds. After initialisation, the LED blinks blue. The app manages the connection automatically. On some mobile devices a window with Bluetooth® wireless connection options appears - please do not connect the N-Tester BT in this window.
  3. If the pairing was successful, you get a signal from the app and the blue LED will stay on.
  4. The app guides you to take an empty measurement against ambient light to calibrate the device. To do so, hold the N-Tester BT head closed for several seconds until your mobile device vibrates.


Note: A red blinking LED during initialisation indicates the batteries need replacing.



4) Measure your crops


After you successfully connected your N-Tester BT to the Atfarm mobile app, you are ready to measure your plants.


Before you start, some tips to achieve optimal results:


  • Your mobile device can remain in your pocket during the measurement.
  • To obtain a representative average reading, the measurements must be carried out randomly distributed across the field, on at least 30 representative plants.
  • To get the best results, move through the field making a W pattern.
  • Avoid atypical field areas, for example, areas with distinctly different soil properties, such as sand banks or similar.



  • Depending on your country and crop, the type of leaf recommended for measuring changes. Choose a plant in the right growth stage, for example, BBCH 30 - 51.



  • Measure in the middle of the leaf blade of the youngest fully developed leaf. Measurements on not fully developed leaves may lead to increased recommendations.
  • Avoid grained or thick points of the leaf, leaves with visible drought stress or leaves rolled together.
  • Make sure that the field has enough sulphur. A sulphur deficiency such as nitrogen deficiency leads to the leaves being brighter and the nitrogen recommendation provided might not be correct. Other nutrients do not have any significant influence.
  • Differences in the varieties will be considered in the app by using correction factors.


Now, you are ready to measure your plants:


Tip: The following steps can be performed with the test disc to practice handling of your N-Tester BT or to check its function. In this case, place the test disc in the measuring head so that the green glass covers the lens.



  1. Place the leaf inside the measuring head using the centre line as a reference. The lens must be covered completely. The leaf adjuster can be moved to adapt to the width of the leaf. If the leave was positioned incorrectly on the measurement head or the leave is too dirty or wet, an error message will occur.
  2. Press the measuring head together by using the thumb rest. Hold until the LED blinks. You will also be notified on your mobile device. An unsuccessful measurement is either indicated by a red LED light or a notification from the app. If this does happen, please repeat the measurement.
  3. Repeat the measurement at least 30 times throughout your field.
  4. When finished, switch off the N-Tester BT with the ON/OFF button.




5) Get the nitrogen recommendation


  1. When you completed your measurements, click on GET N-TESTER VALUE in the Atfarm mobile app.
  2. A nitrogen recommendation in kg/ha will be displayed on your screen.
  3. Click REPEAT MEASUREMENT to restart your measurement.
  4. Click on SHOW MORE INSIGHTS to see more details about your crop.
  5. Click on SHOW N-TESTER VALUES to see the 3-digit values. These values are an intermediate result determined by the N-Tester.


You can find all nitrogen recommendations in the field page.


Please note:

For now, we do not take fertiliser regulations into account for the N-Tester analysis. Please remember to take the maximum nitrogen requirement according to the governmental fertiliser restriction when fertilising your crops.



The Bluetooth® word mark and logos are registered trademarks owned by Bluetooth SIG, Inc. and any use of such marks by Yara International ASA is under license. Other trademarks and trade names are those of their respective owners.

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