This document discusses decision support systems (DSS) in agronomy and crop modeling. It provides examples of how DSS are applied in agronomy through modeling software like Stella and modeling applications like DSSAT and CropSyst. A sample wheat model is described that uses 7 state variables like phenology, water, and biomass to mathematically represent biological and environmental processes. Weather generators, phenology models, and biomass and water balance models are outlined.

1. Decision Support System in
Agronomy: Modeling
 What is Decision Support Systems ?
 What is the role of DSS in Agronomy ?
 How DSS are applied in Agronomy ?
 Sample Wheat Model …
 Open Discussion
Examples and Graphs by Prof. David Conner, University of Mel borne, Australia

2. Definition of Decision Support
Systems in Agronomy
 Mathematical representation of the
Physical, Chemical and Biological
processes involved in Agronomy
System response to the environment
and management.

5. Role of Decision Support
Systems
 Organize existing knowledge focusing on specific
problems.
 Identify research opertuinities and help integrate
research teams.
 Provide cores of decision support systems to aid
management (multiple objectives, variable climatic
and environmental conditions.)

6. How to Apply DSS in
Agronomy ?

7. DSS Application
 Modeling Software
– Stella
– Smile
 Modeling Application
– DSSAT
– CropSyst

8. The Description of the Crop-
The 7 state Variables
 Phenology
– Phenostage
 Water
– Water content of root zone
– Water content of subsoil
 Biomass
– Leaves, living and dead
– Stem
– Grain
 Cultivar
– Development Rate (3 parameters)
– Root extension rate
– Specific leaf mass
– Canopy extinction coefficiency
– Response of growth to temperature
– Response of growth to relative transpiration
– Partitioning factors for leaf, stem & grain.

9. Stella Modeling

10. WEATHER GENERATOR

11. PHYNOLOGY
Development in Response to Temperature
DVR=a(T-Tb)=(T-Tb)/DD , T>Tb
DD= degree days to complete the phase
Development in Response to Daylength – Long Day Plant
DVR= b(L-Kb) , L>Lb
Development in Response to Temperature and Daylength
DVR=(T-Tb)(L-Lb)/DHH, T>Tb & L>Lb
DHH=day degree hours to complete phase

12. BIOMASS
Other issue in Biomass sector
•LAI determined from leaf mass and specific leaf area
•Rule-based partitioning coefficients for grwoth of
organs:
•No stem growth before stem extension
•No grain growth before anthesis
•Mobilisation of stem reverse to grain after
flowering

13. Issues in Water Balance Model
•Two Layers-Root Zone and Subsoil
•Root zone expands as root grow
•Available water is that between field capacity and
wilting point (FC-WP)
•Evapotranspiration considered in two parts
•Soil evaporation f(surface wetness, gap, Etp)
•Transpiration f(root zone water, cover, Etp)
•Relative transpiration defines effect of availability of
water on growth.

14. Sample Wheat Model