Once you've added your fields, you can create and export Variable N-Rate Application maps both in the Atfarm web app in your desktop browser, as explained in this article, and in the Atfarm mobile app on your mobile device.

In the Atfarm web app, you can choose to auto-generate the application map using the VRA algorithms or to draw the application map from scratch using the brush editor and define fertilisation zones and amounts yourself. Either way, you'll be able to adjust the fertilisation zones and amounts using the brush editor.

Tip: You can create application maps for multiple fields of the same crop type at once. Read here how to proceed.

Please note before you start:

• Read here about the equipment required, file types by terminal and how to request a test file.
• The maximum field size for creating application maps is 1,500 ha. The minimum field size is 1 ha with a minimum field width and length of 50 m. Read here about the field sizes.
• To create an accurate application map, ensure that non-crop areas are excluded when adding your fields to Atfarm. When you draw the field, you can add inner boundaries and adjust the outer field boundary.
• We don't currently take fertiliser restrictions into account when creating application maps. When fertilising your crops, please remember to adjust the fertiliser application to comply with government fertiliser restrictions.
• Grassland: You can create application maps for mown grass (not grazed grass) consisting mainly of ryegrass (Lolium sp.), fescue (Festuca sp.) and timothy (Phleum sp.) with no more than 5 % clover in the sward. However, we're already working on calibrating the algorithm for grass with higher clover content.

1) Select your field

Initiate the map creation as follows:

1. Log in to Atfarm from your desktop browser.
2. Select the desired farm in the farm overview.
3. Select the desired field in the field overview.
4. Click Get recommendation and select Variable N-Rate Application.

2) Select biomass

You're now in the VRA Map Builder. A blue badge in the VRA Map Builder saying 'Powered by N-Sensor technology' will indicate that the VRA N-Sensor algorithm is used. Read here about the VRA algorithms.

Proceed as follows:

1. Select the biomass map date from the first dropdown.
   • The application maps are created from biomass indexed satellite imagery.
   • Only cloud-free satellite image dates are listed, as biomass indices can only be applied to cloud-free images. However, sometimes dates are marked as cloudy in the timeline when they're actually cloud-free. Read here how to view cloudy satellite images. Once you've found a recent cloud-free image, select it from the timeline to use it for the application map. In this case, you don't need to select the date of the biomass map from the dropdown.
   • For best results, use the most recent image as it will reflect the current crop status. The image should be no more than five days old, as older images may show biomass values that don't reflect current conditions. When using old images, make sure they reflect the current crop performance.
2. Depending on the crop type, select the growth stage of your crop for the biomass map date from the dropdown.
   
   • The VRA N-Sensor algorithm is based on thousands of samples and lab tests and adapts to the crop and growth stage.
   • We recommend a growth stage based on your crop type. As variable rate fertilisation isn't recommended for each growth stage, these can't be selected.
3. Depending on the crop type and growth stage, click on Levelling or Protein dressing to select the variable rate strategy.
   
   • The levelling strategy applies higher nitrogen rates to areas with lower biomass/nitrogen uptake and lower nitrogen rates to areas with higher biomass/nitrogen uptake.
   • The protein dressing strategy applies higher nitrogen rates to areas with higher biomass/nitrogen uptake and lower nitrogen rates to areas with lower biomass/nitrogen uptake.
   • If you don't see this option, Atfarm has automatically selected the strategy. Read more about the strategies here.
4. Click Continue to N-Rate to proceed to the next step.

3) Add target N-rate

You'll now enter information to be considered in the application map calculation.

Proceed as follows:

1. Enter the target N rate in kg N/ha in the first input field.
   • The target N rate is the average nitrogen rate to be applied to the field. It's the main input to the VRA N-Sensor algorithm. The satellite images provide information about the different nitrogen uptake in the field, but they don't provide actual absolute nitrogen values. You can use the Yara N-Tester to determine the agronomically optimal nitrogen rate for your next application.
2. Enter lower and upper limit in kg N/ha in the next input fields.
   • The lower and upper limits define the minimum and maximum application rates for the applied variable rate strategy. If the field areas with their calculated application rates are outside these limits, the application rates are adjusted to the set limits. If the calculated application rates are within the limits, the limits aren't applied.
   • For the levelling strategy, the lower limit applies to areas with high biomass/N-uptake and to areas with exceptionally low biomass/N uptake (<30 % of average field N-uptake).
   • For protein dressing, the lower limit applies to areas of low biomass/N-uptake.
   • The recommended lower limit is 1 kg N/ha. The upper limit should be at least +/- 10 kg N/ha from the target N-rate.
3. Select the fertiliser you want to apply from the dropdown.
   • The fertilisers that can be selected depend on your country. If you don't see your fertiliser in the list, select Other or Generic.
4. If necessary, adjust the % N in the fertiliser in the next input field.
   • The % N content expresses the nitrogen content in 100 kg of fertiliser.
5. Click Create VRA map to generate the application map.
   • Click Draw from scratch instead to apply the fertilisation zones yourself and enter your own rates. The target N-rate is then no longer the basis for the average N-rate.
   • The application map is saved under Recommendations on the field page, so you can also continue with it later.

4) Review and adapt map

You can now view and customise the application map created.

About the application map:

• The application map consists of a biomass map with the fertilisation pixels as squares or dots depending on the rate adjustment strategy selected. Each colour represents a different nitrogen rate in kg/ha.
• You can see average N in kg/ha, total N in kg, total fertiliser and the cell size.
• Each pixel on the map represents the centre of a 20 x 20 m cell. This design allows you to see the biomass through the pixels. The 20 x 20 m pixel resolution is sufficient for current spreader models (most over 20 m spreading width) and can also be used for spreaders with a larger spreading width.
• Each corner of the field must have a nitrogen value associated with it, even if most of the 20 x 20 m cell is outside the field, so that your terminal can read the application map. You just have to work on the field boundaries as usual. Pixels with areas outside the field boundary are handled by Atfarm's boundary handling algorithm and the application rate is calculated only for the areas of the pixels within the field boundary.
• The cell size refers to the spatial resolution of the pixels from the satellite data. The scaling of the cells depends on the size of the field. The larger the field, the larger the scale (20 x 20 m, 40 x 40 m, 60 x 60 m, 80 x 80 m, etc.). The larger the scale, the lower the spatial resolution of the pixels from the satellite data.

Adapt the map as follows:

1. Click Edit next to the fertiliser name to update target N rate, lower and upper limits, fertiliser and % N in fertiliser. When finished, click Update to recalculate the application map.
2. For auto-generated maps only: Click on Zone Map or Raster Map to select the rate adjustment strategy.
   • Zone map: Neighbouring pixels with similar N-uptake and corresponding nitrogen levels are grouped into zones. The gradations are created in 10 % steps. This makes it easier to use spreaders which have +/- 10 % buttons. The zone map is best used for manual applications or older terminals. When using the Atfarm mobile app as a terminal and selecting to spread by speed, the zone map is coarser and is therefore recommended as less manual control of the spreader is required.
   • Raster map: The N-uptake and application rate are calculated per pixel and the fertiliser is applied accordingly. The raster map is designed for maximum precision on high-end equipment.
3. Use the brush editor to change the fertilisation zones and amounts. This is optional for auto-generated maps and required for maps drawn by scratch.
   • Click on the number below a colour and enter the desired nitrogen rate.
   • Click on a colour to select it, then click on a fertilisation zone on the map to apply the new rate.
   • Use the + and - buttons on the map or your mouse wheel to zoom in and out.
   • Click Undo to undo your last change.
   • Click Reset to clear all changes.
   • To disable the brush, click on the selected colour again.
4. Click Continue to export to proceed to the export.

5) Send map to your phone

You'll now see the application map with different coloured pixels. The pixels represent the application zones with different amounts of fertiliser in kg/ha to be applied to achieve the target N-rate. A colour scale on the map shows the amounts per colour.

Export the application map as follows:

1. If necessary, click Edit next to the fertiliser name to change rate adjustment strategy and fertilisation zones and amounts. When finished, click Export to recalculate the application map.
2. Click the download icon next to the Send to phone option.
   • If desired, select the PDF option to also save the application map as a PDF file. This is ideal for sharing and printing.
3. A pop-up confirms the success of the export to the Atfarm mobile app.

6) Create application task

The application map has been exported to the Atfarm mobile app and you can now create the application task as follows:

1. Log in to the Atfarm mobile app on your mobile device.
2. Select the desired farm in the farm overview.
3. Select the field which you created the application map for in the field overview.
4. Click View application maps in the application maps section.
5. You should now see your application map in the list of created application maps.
   • It may take a few minutes for the application map to appear in the Atfarm mobile app.
   • If you still can't see the application map, please ensure that you've updated the app to the latest version. If the issue persists, try logging out and logging back in, restarting your mobile device, or reinstalling the Atfarm mobile app.
   • For assistance, please contact our support team.
6. Click on the application map to open it.
7. Click Create application task to create the application task.
8. You can see the task outline with details: fertiliser to be applied, total fertiliser, mid flow rate in kg/ha.
9. Select the driving mode with the green switch. We use your GPS location to determine the application rate, so you can manually adjust the driving speed or flow rate as you drive.
   • Spread by speed
     • If it's not possible to adjust the spreader's flow rate while driving, use this mode to adjust the driving speed. The app detects which application zone the tractor is in and it's current speed and displays the speed to drive at to achieve the desired result.
     • Using tractors with a low number of gears, or where changing gears requires the clutch to be pressed, can result in uneven driving and unwanted spreading. Therefore, the tractor should have several gears in the speed range. To avoid a drop in speed when changing gears, it's recommended to use a tractor with a power shift or CVT or IVT transmission.
   • Spread by flow rate
     • If the spreader terminal has a manual control system and can adjust the flow rate while driving, use this mode to adjust the fertiliser application by means of the spread rate. The app will then indicate how much to manually increase or decrease the spread rate on the spreader terminal based on the application map.
10. Spread by speed only: Enter your preferred mid speed under Calibrate mid speed. The driving speed range will be adjusted accordingly.
11. Click Start driving.
12. Activate location tracking on your mobile device, so the application rate can be adjusted based on your current position in the field.
    • Set the GPS accuracy of your mobile device to a high level.
    • The GPS accuracy may be limited in forested areas and deep valleys.

7) Start the application

You'll see a map showing your current position on the field. Prepare your equipment and begin your variable application as follows:

1. Mount your mobile device in the tractor cabin.
2. Adjust the spreader settings for the mode you've chosen:
   • Spread by speed: Set your spreader to the mid flow rate and tractor to the mid speed shown on the screen.
   • Spread by flow rate: Set your spreader to the mid flow rate shown on the screen.
3. Start driving and follow the instructions shown in the app.
   • Spread by speed: Maintain the driving speed shown in the app.
   • Spread by flow rate: Follow the flow rate shown in the app.
4. To stop the application and continue at a later time, simply go back in the app or close the app. The application task is saved under the field or in the Tasks tab.
   
   1. Click View application tasks in the tasks section.
   2. Click on the task in the list of tasks to open it.
   3. Click Start driving to continue with the task.
5. To complete the application task, click Mark as completed in the app.
6. Click Confirm job complete to complete the task.
   • Click Continue driving to continue with the application task.
   • The completed application task with details of the driver, date, area and time can be found under the field or in the Tasks tab.