What do the zones on a variable-rate application map mean?

A variable-rate application map in YaraPlus Atfarm shows coloured application zones in your field based on satellite analysis of crop growth (biomass).

Satellite images consist of small square areas called pixels. Each pixel represents a small area where crop biomass is estimated. YaraPlus Atfarm analyses the images and automatically groups neighbouring pixels with similar biomass values into application zones.

Each zone represents a recommended nitrogen rate (kg N/ha). Based on this nitrogen rate, YaraPlus Atfarm also calculates the required fertiliser rate in kg/ha for the fertiliser you selected. These recommendations are based on satellite-derived crop growth data and should always be considered together with your own field knowledge and local conditions.

Application zones represent general differences in crop growth across the field. The zone boundaries are calculated from satellite data and may not exactly match visible differences in the field.

What the colours on the map mean

Each colour on the map represents a different nitrogen rate (zone).

The colours correspond to the values shown in the map legend. Depending on the selected view, the legend shows either:

• Nitrogen rate in kg N/ha
• Fertiliser rate in kg/ha

The fertiliser rate is automatically calculated from the nitrogen rate based on the fertiliser selected for the map.

When creating a map, you can choose how many zones the field should contain. Each zone represents one nitrogen or fertiliser rate. The more zones you choose, the more detailed the variation in nitrogen rates can be.

How nitrogen rates are determined

The nitrogen rate in each zone depends on the application strategy selected in YaraPlus Atfarm.

Application strategy	Higher nitrogen rate applied to	Goal
Levelling	Areas with lower biomass (weaker crop growth)	Create a more uniform crop across the field
Protein boosting	Areas with higher biomass (stronger crop growth)	Increase protein in high-performing areas

Levelling is typically used for earlier fertiliser applications to improve crop uniformity across the field.

Protein boosting is typically used for later fertiliser applications to increase protein in the strongest areas of the field.

This means that the same biomass pattern can lead to different nitrogen rates, depending on the selected application strategy.

Map types in YaraPlus Atfarm

YaraPlus Atfarm offers two map types for applying variable rates in the field:

• High precision for automatic variable-rate application
• Simplified for manual application

High precision maps calculate nitrogen uptake for small areas across the field. The resulting nitrogen rates are applied as many small application zones. This map type allows the fertiliser rate to change frequently across the field and is designed for use with terminals and spreaders that support automatic variable-rate application.

Simplified maps group neighbouring pixels with similar nitrogen uptake into larger zones. This reduces very small zones and creates smoother transitions between application areas. The nitrogen levels are displayed in steps of 10 %, making the map easier to use with spreaders that allow the operator to adjust rates manually using +/-10 % adjustments.

Both map types are generated from the same satellite data but present the application rates differently. Switching the map type changes how nitrogen rates are displayed and grouped in the field.

Why application zones have different sizes

Application maps are created from satellite imagery that estimates crop biomass. YaraPlus Atfarm analyses this data and divides the field into square application zones where a nitrogen rate is calculated.

The size of these zones can vary depending on the size of the field. Smaller fields often use zones of around 20 × 20 m, while larger fields may use larger zones such as 40 × 40 m, 60 × 60 m or 80 × 80 m.

A zone size of 20 × 20 m works well with most modern fertiliser spreaders and sprayers. These machines typically have a working width greater than 20 m and can automatically adjust the application rate while moving across different zones of the application map.
 

Larger zones help avoid creating a very large number of small areas and make the map easier to apply reliably with agricultural machinery. This also reduces the number of rate changes during fertilisation, making larger zones suitable for wider spreaders or machines that require more time to adjust the fertiliser rate.

How application maps work during fertilisation

During fertilisation, the machine automatically adjusts the fertiliser rate based on its GPS position within the zones of the application map.

If the working width of the spreader or sprayer is larger than the zone size, one pass of the machine may cover more than one zone. In this case, the terminal adjusts the fertiliser rate according to the machine's position in the map, and the machine applies this rate across the entire working width.

Because fertiliser spreaders and sprayers distribute fertiliser across a wide spreading or spray pattern, transitions between zones occur gradually rather than as sharp boundaries. This behaviour is normal and doesn't affect the effectiveness of the application.

If the zone size is larger than the working width of the machine, several passes may be made within the same zone. During these passes, the fertiliser rate remains the same and only changes when the machine enters the next zone.

Machine features such as section control

Many modern spreaders and sprayers support technologies such as section control or nozzle control. These systems automatically switch parts of the machine on or off to reduce overlaps at field boundaries, headlands or irregular field shapes.

Machines with nozzle control can adjust the application rate more precisely across the working width, while machines with section control apply the same rate across each section.

Variable-rate application maps control the fertiliser rate, while section control manages overlap. Both technologies can work together during field application.

Manual application

If you select Simplified maps for manual application, the map shows larger zones with nitrogen levels in steps of 10 %.

The operator uses the map as guidance and manually adjusts the fertiliser rate when moving between zones. This can be done, for example, using +/-10 % adjustments on the spreader or terminal.

This approach allows basic variable-rate fertilisation even without automatic rate control.

Editing nitrogen or fertiliser rates

After creating a map, you can manually adjust the values for each zone.

In the Edit zones view, you can:

• edit the nitrogen rate (kg N/ha) for each zone
• edit the fertiliser rate (kg/ha) for each zone
• switch between High precision and Simplified map types
• use the brush tool to manually adjust map areas

This allows you to adapt the map if you want to fine-tune the automatically generated values for your field conditions.