42
P. Cepuder and V. aus-der-Schmitten
COC) (no growth occurs at or below Tb) of crop j. A heat-unit index (HUI) ranging
from 0 at planting to 1 at physiological maturity is computed as follows:
HUI; = 6=1:2 HUJ / PHU;,
(11)
where HUI is the heat unit index for day i and PHU is the potential heat units
required for the maturation of crop j. The value of PHU may be inputted or
calculated by the model from normal planting and harvest dates. Date of harvest,
leaf area growth and senescence, optimum plant nutrient concentrations, and
partition of dry matter among roots, shoots, and economic yield are affected by
HUI.
2.3 Empiric Formula
The EPIC model requires additional soil parameters which can be calculated by
empiric formula. For the given problem, the formula of Baumer (Baumer 1989)
showed correlating results and are used for modeling. These formulas are an
expert system to computer-generate soil hydraulic parameters from individual
field observations or specific laboratory-generated data. The system is set up so
that it can accept minimally required input data up to a broad array of
measurements. The required input data are horizon depths, coarse material
content, soil texture, organic matter, clay activity, and relative compaction.
The output includes a complete soil water retention curve, a hydraulic
conductivity function, an estimate of the saturated hydraulic conductivity for each
horizon, all parameters in the Green - Ampt infiltration equation, and a maximum
upflux value from various water table depths.
For the EPIC simulation, the following parameters are calculated with the
formula of Baumer:
• Field capacity
• Permanent wilting point
• Plant available water content
• Saturation
• Bulk density
• Hydraulic conductivity
Model calibration was carried out with the results of the Austrian soil status
inventory (Blum et al. 1996), and the correlation was found to be sufficient.
3 GIS Application
In order to organize, manipulate, analyze, and view spatial data, the desktop-GIS
ArcView is used. Within the GIS, all nonspatial data can be managed and
functions and calculations such as empiric formulas directly integrated in
dialogues and scripts. The EPIC model written in FORTRAN programming
language can be run out from the GIS. Linkage of GIS, simulation model, and
P. Cepuder and V. aus-der-Schmitten
COC) (no growth occurs at or below Tb) of crop j. A heat-unit index (HUI) ranging
from 0 at planting to 1 at physiological maturity is computed as follows:
HUI; = 6=1:2 HUJ / PHU;,
(11)
where HUI is the heat unit index for day i and PHU is the potential heat units
required for the maturation of crop j. The value of PHU may be inputted or
calculated by the model from normal planting and harvest dates. Date of harvest,
leaf area growth and senescence, optimum plant nutrient concentrations, and
partition of dry matter among roots, shoots, and economic yield are affected by
HUI.
2.3 Empiric Formula
The EPIC model requires additional soil parameters which can be calculated by
empiric formula. For the given problem, the formula of Baumer (Baumer 1989)
showed correlating results and are used for modeling. These formulas are an
expert system to computer-generate soil hydraulic parameters from individual
field observations or specific laboratory-generated data. The system is set up so
that it can accept minimally required input data up to a broad array of
measurements. The required input data are horizon depths, coarse material
content, soil texture, organic matter, clay activity, and relative compaction.
The output includes a complete soil water retention curve, a hydraulic
conductivity function, an estimate of the saturated hydraulic conductivity for each
horizon, all parameters in the Green - Ampt infiltration equation, and a maximum
upflux value from various water table depths.
For the EPIC simulation, the following parameters are calculated with the
formula of Baumer:
• Field capacity
• Permanent wilting point
• Plant available water content
• Saturation
• Bulk density
• Hydraulic conductivity
Model calibration was carried out with the results of the Austrian soil status
inventory (Blum et al. 1996), and the correlation was found to be sufficient.
3 GIS Application
In order to organize, manipulate, analyze, and view spatial data, the desktop-GIS
ArcView is used. Within the GIS, all nonspatial data can be managed and
functions and calculations such as empiric formulas directly integrated in
dialogues and scripts. The EPIC model written in FORTRAN programming
language can be run out from the GIS. Linkage of GIS, simulation model, and