After you added your fields, you can create and export your VRA map by following these steps:
- Open Atfarm.
- Select your farm you want to create the VRA map for.
- Select the field you want to create the VRA map for.
- Click 'Get recommendation'.
- Choose 'Variable-rate application maps'.
- Choose the biomass map date. You should use the latest cloud-free image.
- Select the growth stage of your crop for the date the biomass map image was taken.
- Click 'Continue'.
- Enter the target N rate, the lower and upper limit, the fertiliser and the % N content.
- Click 'Generate automatically' (calculation based on the N-Sensor vegetation index/N-Sensor biomass image) or 'Create manually' to create your VRA map manually.
- If you chose to generate the VRA map automatically, you now choose between zone and raster map. If you chose to create the VRA map manually, you can now adjust your field with the brush editor.
- Click 'Export'.
- Your VRA map is now saved in Atfarm. Choose between the displayed terminal export options and the export to our free Atfarm Mobile App on your smartphone.
- Click on the download symbol next to the export options you have chosen.
- Your VRA map will now be saved as a .zip file to your computer/sent to your Atfarm Mobile App on your smartphone.
You can export the VRA maps directly after creating them or you can export them any time afterwards. You can find your saved VRA maps in your field details view.
Now you can transfer your VRA map to your terminal.
Why am I warned by the system that the satellite image is older than five days?
The variable rate application (VRA) maps are created based on biomass images. The best practice is to create a VRA map with a current image since it reflects the current status of the crop. Older images could potentially display biomass values that don't represent the current condition. So when using old images you need to ensure that they reflect the current performance of the crop on the field.
Why do I need to select a growth stage?
We recommend a growth stage depending on the crop you choose. Our algorithm works based on thousands of samples and laboratory tests and adapts to the crop and growth stage.
Required information for creating VRA maps
The target N rate is the average nitrogen rate you want to apply on your field. It's used as the main input value for the algorithms. The satellite images provide information about the different nitrogen uptakes in the field, but they don't provide suitable absolute nitrogen values to work with. You can use our N-Tester to determine the agronomically optimal N-amount for your next application.
The lower and upper limit are setting limits for the N-Sensor algorithm to provide the possibility to adjust it to your level of confidence.
Choose the fertiliser you want to apply on your field in a drop-down list. If your fertiliser is not in there, please read below.
The % N content expresses the content of nitrogen in 100 kg of fertiliser.
My fertiliser is not in the drop-down list
Which fertilisers are offered to select is based on your country. If your fertiliser shouldn't be in the drop-down list, please select 'Other liquid fertilisers'/'Other solid fertilisers'. Then click 'Create manually'. Now you can manually draw the VRA map.
Manually creating VRA maps with the brush editor
You can adjust and edit your VRA map with the brush editor and adjust fertilisation zones and amounts.
To adjust the fertilisation amount of the each brush colour, follow these steps:
- Click on the number below a certain brush colour.
- Change the number.
- Now the fertilisation amount of the brush colour is adjusted and all pixels of this colour will automatically be updated with the new nitrogen amount.
To change the fertilisation zones on your VRA map, follow these steps:
- Choose a brush colour with the nitrogen amount you want to apply to a certain part of your field by clicking on it.
- The brush is now enabled. Your cursor switched to the selected colour. To disenable the brush, click again on the brush colour.
- Click with the brush on the pixels on your VRA map you want to change.
- The colour of the specific pixel will change into the colour you chose.
Tip: You can zoom into the VRA map with the plus-sign or with your mouse scroller to draw more accurately.
The cell size refers to the spatial resolution of the pixels from the satellite data.
'Zone Map' and 'Raster Map'
If you created your VRA map automatically, you can choose between zone and raster map.
If you create your VRA map as a zone map, the rates are clustered in areas of equal value. The gradations are created in 10 % steps. This makes it easier to use your spreaders that have +/- 10 % buttons. The zone map is best used for manual application or older terminals.
If you create your VRA map as a raster map, the rate is calculated per cell. Using the raster map will provide you maximum precision for top of the line equipment.
Why are there gaps between the pixels of the VRA map? Why are there application pixels outside the field boundaries?
Every pixel on the VRA map represents the center of a 20 x 20 m square. By using this design we enable you to see the biomass of your field through the pixels.
Every corner of the field needs to have an N-value attached to it, even if most of the 20 x 20 m square lie outside of the field. So your spreader can read the VRA map, You just need to work on the field boundaries as you usually do.
Which file type to export
The file type you need to download depends on your spreader terminal type. You will find this information in the user manual of your spreader terminal.
To check the compatibility of your terminal and spreader, you can contact our Customer Support Team and request a test file. We will send you the file with instructions, so that you can quickly check the compatibility of your equipment.
Creating VRA maps for multiple fields at once
Unfortunately, you can only create VRA maps for one field at a time. But we are working on improving our software.