Using Chlorophyll Maps to create N Prescription maps
In this tutorial, you can download a sample dataset with Chlorophyll Maps layers, and review sample applications, including:
- Variability analysis → improves the knowledge about within-field variability, supporting management decisions, creating management zones, selecting areas for research, etc.
- Support for directed sampling → Using the Chlorophyll Maps for directed sampling, the agronomist can find limiting factors.
- Creating Prescription maps → Chlorophyll Maps can be used as base maps for N prescription maps.
Download sample data
For these exercises we are going to use a sample dataset: Sample_Farm_Chlorophyll_Map. For this purpose, you can follow the steps detailed in Download Sample Data
- Create new Project with the name: 'Sample Farm - Chlorophyll Map'
- As the initial dataset, select Sample_Farm_Chlorophyll_Map.gis, which can be found under the Tutorials_en folder:
The first step is to analyze all the information related with the sample Chlorophyll map.
We have a field in Canada, close to the border in North Dakota, and a chlorophyll map series, from 7/17/2009 - 8/1/2009 - 8/21/2009 - 8/25/2009.
- Double click on the layer 'RE20090801...' to make it active and zoom to its extents.
- Turn On Chlorophyll layers/maps for each of the dates in ascending order
- Display the legend for the chlorophyll values, by clicking on the '+' sign to expand the legend to see how is the map classified
Values closer to green indicate higher levels of chlorophyll, which is rated from 1 to 8, where 8 is the highest.
Create an N Prescription map
After ground truthing the information, we've validated that there is a close relation between map values and N availability in the field.
Please review the GPS Module, and this tutorial: Plan your field visit and download points to your GPS device, to learn more about working with a GPS device for ground truthing purposes.
After the field visit, we then decide to do an in-season fertilizing operation, for chlorophyll classes 2, 3, 4, and 5 in the map.
We assume that we have applied a base rate of 100 pounds per acre, and now we'll apply additional N in a rate of 80 pounds in classes 3 to 6 , and 0 pounds in the rest. Since we are going to apply Urea (46% N), we need to apply 175 lbs/ac of Urea.
- Open the Drawing Tools in the Left Panel, and then Select the Prescription tool to start the prescription wizard.
- Select the reference layer, based on which the N prescription will be created. Click on Next >.
- Define recommended input rates, entering the following values:
In the right side:
- Operation: N fertilizing
- Input: Urea
- Unit: lbs/ac
In the left side, enter 2 rates: 175 (lbs/ac), and 0 (lbs/ac), and their corresponding color, in the blue and yellow tones respectively.
Please note that if you are going to standardize rates in your operation, it's a good idea to use the Save option in the screen above to save the rates and colors definition for future use.
- Next, assign the rates to the chlorophyll classes. Let's assign rates of 175 lbs/ac for areas with 2,3,4 and 5 levels, and 0 lbs/ac to the remaining areas.
Also, click on the 'Join polygons of the same class' option, so the polygons of the same class will be joined in the resulting layers
- Next, enter the name of the layer where the prescription map will be saved:
- Name: N Fertilizing
- Group: [New Group], in the new group field enter: N Fertilizing
- Structure: Prescription (this value cannot be changed)
- Click on Finish, and expand the 'N Fertilizing' layer just created.
|Tip:||Use the Layer transparency option to show the chlorophyll layer underneath, and how it corresponds to the prescription layer.|