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| - | ==4.2. Preparation of polygons for main crop growing areas in the country and define cropping practices and conditions.== | + | |
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| + | ==4.1. Defining cropping practices and conditions and preparation of polygons for main crop growing areas in the country.== | ||
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Revision as of 08:52, 4 October 2006
4.1. Defining cropping practices and conditions and preparation of polygons for main crop growing areas in the country.
In order to do any meaningful crop forecasting, crop conditions should be take into consideration. First of all it needs to be clear where crops are grown. The crop growing areas will be digitized for use with the CM Box software. Secondly, some characteristics on crops related to local practices will have to be recorded.
Gathering crop information
The FAO Water Balance model is using the following additional crop information:
- Planting dates. Planting dates occur rarely on the same dekad every year. However, in most circumstances it is possible to establish a “window of opportunity” for planting lasting 1 to 3 months. As an example, this window of opportunity for maize is October – December in large parts of Southern Africa.
- Irrigation. The water balance calculations are can take irrigation into account. If irrigation will be applied it needs to be clear how much. Possibilities are : a fixed amount in mm per dekad, different amounts for different dekads and an automatic amount of irrigation that prevents water stress.
- Cycle lengths in dekads. Every crop variety has its own cycle length. Usually in arid areas, crop lengths are shorter than in wetter areas.
- Water Holding Capacity. This is the maximum amount of soil water available to the crop within root range (in mm).
- Crop Coefficients. Crop coefficients can be set with the AgrometShell Database-Configure-Crop Coefficients function.
Preparation of polygons for main crop growing areas
In the following example a map will be created in right format (BNA) of the millet growing area in India.
USDA / NOAA has created a simple map that roughly denotes millet growing areas in India. 
Digitizing can be done by hand, but far more convenient is to use Windisp. A vector map of India is loaded into Windisp to be displayed in the background, using the File-Open-Map function. This will facilitate digitization. 
A new polygon will be digitized onto this map with the Draw-Map-Region function. The name of the boundary file will be millet.bna. Theline color and thickness is set such, that easy digitizing is accomlished. 
The first millet growing area is now digitized. After all millet growing areas have been finished the boundary file millet.bna is completed. 
Far more extended software is available for digitizing maps. Even automatic digitization from bitmaps is possible. A very good freeware digitizing application called Wintopo, can be downloaded here: http://www.softsoft.net/wintopo/dl-wintopo.htm
