Creating variable rate prescription map for Fertilizing based on Relative biomass - satellite imagery

This guide explains how to create a fertilization prescription map based on relative biomass using satellite imagery in the CultiWise application. It covers the steps to initiate, configure, and download the prescription map. 

By applying different fertilizer rates to specific field zones based on relative biomass data from satellite images, you can optimize nutrient distribution, improve efficiency, and enhance crop performance.

Note: Satellite based fertilizing provides quick and easy access to fertilizing maps with no need for capturing drone data.

Creating a Fertilizing Prescription Map Using Satellite Data

To start click 'CREATE PRESCRIPTION', select the 'Fertilizer' group, and then choose 'Based on Relative Biomass'.

A pop-up window will appear. Select 'CREATE FROM SATELLITE IMAGERY'.

Accessing satellite imagery

For you to be able start crating prescription map, first you have to choose satellite imagery from calendar and show the layer displaying this imagery by clicking on 'SHOW LAYER'. After that option 'GENERATE ZONES' become available. 

Note: See the guide on how to understand calendar with satellite imagery below.

Color-coded markers under the date indicate the availability of imagery from specific sources (refer to the legend):

• Orange: Sentinel-2 imagery available (approximately two images per week, 10m ground sampling distance)
• Green: Planet imagery available (up to daily images, 3m ground sampling distance)

Selecting an Imagery Date

Click on a date to see the types of satellite imagery available.

Cloudiness

An icon on the right side will indicate either the cloud cover for the selected date or the service status:

• 0% cloud cover: Ideal conditions
• <0% cloud cover: Higher cloud cover reduces image quality
• N/A: The service is not activated (applies to Planet imagery)

If both services are available, only one has to be selected to show base layer upon which one the zone map will be created.

Select layer

When viewing satellite imagery, different indices can be selected and displayed on the map. Each index highlights specific vegetation conditions:

• NDVI: Indicates vegetation health and density
• Chlorophyll Index: Estimates leaf chlorophyll levels
• Crop Moisture Index: Identifies drought stress in crops
• Leaf Area Index: Measures total leaf coverage per area

Select gradient map

• Adjust the color scheme to represent index values.

Index histogram 

• Allowing you to customize scale values and range for enhanced contrast and improved visual clarity.
• The histogram typically features two peaks: the first represents soil (lower vegetation values), while the second corresponds to vegetation. The slider can be adjusted to narrow the range and highlight differences more effectively

Generating zones

Zone count

• You can define 2 to 10 zones.
• Fields with greater vegetation variability may benefit from a higher zone count.
  
  

Smoothing

• Higher smoothing levels eliminate small areas and create smoother zone boundaries.
• While this can help prevent issues with sprayer accuracy on complex maps, excessive smoothing may result in a loss of detail.

Note: Adjusting opacity, gradient, or the histogram slider does not affect the actual variable rate map; it only changes the display settings of the selected vegetation index.

Once all settings are configured, click 'GENERATE ZONES' to create the zone map. You can continue adjusting and regenerating zones as needed.

Note: Generated zones remain as temporary layers until saved as a prescription map. Adjust zone count, smoothing, or resolution if the results do not meet your requirements.

To apply the desired product amount across field zones, start by entering data and setting up an automatic distribution strategy. After the calculation, if you're not satisfied with the result, you can reenter the inputs or manually adjust the rates.

Rate unit

• Select the appropriate unit based on the applied product. The Standard Rate represents the rate typically used for a broadcast application.

Strategy

• Choose whether to apply a higher dose to: Strong zones (denser vegetation) or Weak zones (less developed vegetation).

Decrease in weakest zone

• Define the percentage decrease in application rate for the weakest zone compared to the standard rate.

Increase in strongest zone

• Define the percentage increase in application rate for the strongest zone compared to the standard rate.

Rates for each zone can be adjusted manually. Volume savings are calculated based on the standard rate, which can be modified above the chart for calculation purposes only.

Rates can be adjusted using two strategies:

• Force Edit Total Amount - Adjusts all rates proportionally to match a predefined total product amount.
• Force Edit Average Rate - Adjusts rates to maintain a specified average application rate per hectare.

At the end, you can rename the map (layer name) and select the correct machine type.

Note: Most sprayers and terminals support the generic VRA map format.

Generated map will be available under the dataset from which it was created. It can be exported for use with compatible machinery and software.

• To export the prescription map, click 'EXPORT AS .SHP' below the map legend.
• This will generate a shapefile compatible with agricultural machinery and software.