After adding your field, you can see a satellite map of the field with a biomass layer on it.

You can select 3 types of biomass maps to view the in-field variability. Click on the map layer tile in the lower right corner of the field map and choose between

• NDVI (Normalized Difference Vegetation Index) map

• Optimised map

• N-uptake map

NDVI (Normalized Difference Vegetation Index) map

Our NDVI map uses the Normalized Difference Vegetation Index (NDVI) to display the nitrogen deficiency on targeted vegetation. With this map you can quantify the difference between healthy and stressed vegetation.

The Normalized Difference Vegetation Index (NDVI) measures the reflection of red and near-infrared light from the vegetation. It then determines a relative value between 0 and 1, which indicates whether or how much green biomass is existent. Biomass levels are shown using a fixed green colour scale. Dark green areas are representing high biomass availability while light green areas are representing low biomass.

But this index has a limitation. From shoot development and onwards (canopy saturated, highest biomass) it saturates very quickly and differences between highest and lowest growth can no longer be recognised.

Please use our NDVI map only in early growth stages for planning your first application. For the following applications use our optimised map or the N-uptake map.

Optimised map (N-Sensor map)

Our optimised map is based on our Yara N-Sensor Index, which makes Atfarm's biomass maps special. We developed this index based on our expertise in precision fertilisation and over 25 years of field trials with our Yara N-Sensor.

Our Yara N-Sensor Index measures not only red and near-infrared radiation as the Normalized Difference Vegetation Index (NDVI), but also the spectral ranges in between. With this fine gradation and the inclusion of crop and regional data, we can determine the N-uptake even for advanced growth stages. With our optimised map you can not only analyse crops and identify differences in N-uptake through the whole growth cycle but also across seasons.

Our Yara N-Sensor Index is insensitive to different growth stages and canopy saturation. It does not tend to saturate as quickly as the Normalized Difference Vegetation Index (NDVI). Depending on the crop type, saturation of our index first starts at about BBCH 50 - 60.

The colour scale is a relative scale without absolute values. The colours adjust based on lowest and highest index values in a satellite image. Low nitrogen uptake is represented by brown tones. A variety of green shades is representing the canopy evolvement. As the canopy evolves, the colour changes to blue and purple shades.

N-uptake map

Our N-uptake map indicates the day specific absolute N-uptake. Each pixel is associated with an N-uptake value. The absolute in-field N-uptake in kg N/ha is calculated from cloud-free satellite images. This makes the N-uptake map ideal for identifying N-uptake variation within a field.

The legend makes use of a colour scale from yellow to dark green and visualises a dynamic scale. Yellow represents the lowest kg N/ha, which is -30 of the daily average, while dark green represents the highest amount of kg N/ha, which is +30 of the daily average.

Our N-uptake map is currently available for various crops, where the N-uptake layer is accurate for specified growth stages and less accurate for unspecified ones: