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Entering data for a crop water balance calculation
For a water balance calculation the following data are needed:
Weather data
- Actual Rainfall for the period of he water balance calculation (up to the current dekad). There are three ways to read these data into AgrometShell.
- Using the Database-Weather-Dekad function.
- When the data come as ASCII files, using the Database-Import-from ASCII file
- When the rainfall comes in the form of images, it can be imported through the Database-Import-from image function.
- Normal Rainfall for 36 dekads in the year. These data can be read into AgrometShell in the same way as actual rainfall.
- Actual ET0 data for the season up to the current dekad. The ET0 data can be calculated from its base data (temperatures, windpeed etc.. ) using the Database-Calculate-Formula function or the Tools-Potential ET-from file function. In case the ET0 values are already calculated, the can be entered in the three ways mentioned above. Although actual ET0 data will improve the outcome of the water balance calculation, AgrometShell can use normal values instead.
- Normal ET0 data for the season up to the current dekad. As outlined for actual data, the normal ET0 data can be either calculated or entered manually. The water balance calculation needs a full year of dekadal ET0 data to calculate the water balance.
- Irrigation amounts. This setting is important for use in irrigated rice simulations.
Crop data.
- Crops. Which crops are grown? Each crop has its own crop coefficients.
- Planting dekads. In which dekad planting occurred?
- Cycle length of the crops grown.
Soil related input data
- Water Holding Capacity of the soil.
- Percentage Effective Rainfall. This parameter is non-essential and is usually kept at 100%. It is meant to account for run-off (values lower than 100%) or run-on (values higher than 100%)
- Pre-season crop coefficient. This is the “crop” coefficient for bare soil (usually around 0.15).
Preparing a water balance
After checking the availability of data a water balance can be prepared through the function Water Balance – Monitoring Run – New. The following window is shown:
The manual ET0A new name the run is specified. “Afghanistan Wheat 2003” is specified. A station list called "Rainfall monitoring network" is selected as a basis for the weather data. The selected crop is wheat. This crop is cultivated in almost all districts of Afghanistan, partly supplied with water trough irrigation. 
The manual ET0A new name the run is specified. “Afghanistan Wheat 2003” is specified. A station list called "Rainfall monitoring network" is selected as a basis for the weather data. The selected crop is wheat. This crop is cultivated in almost all districts of Afghanistan, partly supplied with water trough irrigation. In the following screen you can enter all the data needed for the water balance. The rainfall and PET are entered elsewhere (see previous chapters).||
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