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Crops
Limiting factors for yield
Monitoring crops with a water balance calculation is possible as long as water is a limiting factor for the crop. In circumstances where water is not a limiting factor in any way, water balance output will not be strongly correlated to yields obtained. Limiting factors for crop growth can be grouped into four groups:
- Weather dependent, such temperature, solar raddiation, rainfall and CO2 content of the air.
- Crop dependent, such as genetic potential and crop canopy (LAI)
- Related to Pests and diseases (insects, weeds etc..)
- Related to cultivation techniques (irrigation, fertilizer etc..)
Basically, water balance calculations have predictive value for yield in arid and semi-arid areas. In areas where temperatures are high and water is not limited, solar radiation is loosely correlated to yields. In areas of abundant water and high solar radiation during the growing season, temperatures are often more limiting than other factors (e.g. Northern pats of Russia and Canada)
Limiting factors for yield
Monitoring crops with a water balance calculation is possible as long as water is a limiting factor for the crop. In circumstances where water is not a limiting factor in any way, water balance output will not be strongly correlated to yields obtained. Limiting factors for crop growth can be grouped into four groups:
- Weather dependent, such temperature, solar raddiation, rainfall and CO2 content of the air.
- Crop dependent, such as genetic potential and crop canopy (LAI)
- Related to Pests and diseases (insects, weeds etc..)
- Related to cultivation techniques (irrigation, fertilizer etc..)
Basically, water balance calculations have predictive value for yield in arid and semi-arid areas. In areas where temperatures are high and water is not limited, solar radiation is loosely correlated to yields. In areas of abundant water and high solar radiation during the growing season, temperatures are often more limiting than other factors (e.g. Northern pats of Russia and Canada).
Crops implemented in CM Box
AgroMetShell comes with a number of pre-defined crops. These crops have been selected as they are important in terms of crop forecasting for food security. The following crops are implemented:
- Maize
- Millet (bulrush)
- Tef
- Beans (haricot)
- Wheat
- Sorghum
- Finger millet
- Flooded rice
- Upland rice
The crops implemented in AgrometShell can be displayed with the Database-Configure-Crops function.
Crop coefficients
In the FAO water balance model, the water use of crops is based on weather factors aggregated in the ET0, the water availability through rain, soil and irrigation and the crop coefficients. Crop coefficients describe the relationship between ET0 and water use at every stage of crop growth. Crop coefficients differ from crop to crop and even from crop variety to variety. Therefore more than one set of crop coefficients can be implemented in CM Box.
Viewing and changing crop coefficients.
To view and change crop coefficients, the Database-Configure-Crop Coefficients function is activated. In the window the "default" set of crop coefficients for "Maize" is shown. The curve is independent of cycle length and is fitted through 9 value pairs.
Defining new crops
Defining new crops requires two steps. First the crop itself needs to be defined. Then one or more sets of crop coefficients are defined.
Defining the crop.
In this example the crop “Barley” is added. The crop number and the crop code identify the crop for AgrometShell. The Deficit Threshold is important for irrigated crops. This factor is explained elsewhere. The ReduceValue and the AccessAmount are defined for water excess circumstances. In this example, the final index will be reduced by 3 points whenever the water exces exceeds 100 mm.
Defining the crop coefficients.
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