1. General Model Information

Name: Crop Systems

Acronym: CROPSYS

Main medium: air+terrestrial
Main subject: biogeochemistry
Organization level: ecosystem
Type of model: ordinary differential equations
Main application: research, education, decision support/expert system
Keywords: crop growth, process-level, multiple cropping systems, modelling system, multiple growth models, Ceres, Cropgro, DSSAT,


Robert M. Caldwell
University of Hawaii at Manoa,
College of Tropical Agriculture and Human Resources,
Department of Agronomy and Soil Science,
1910 East West Road
Honolulu, HI 96822

Phone: (808) 956-6835
Fax: (808) 956- 6539
email: rcaldwel@Hawaii.edu
homepage: http://agrss.sherman.hawaii.edu/caldwell/caldwell.htm
Homepage: http://agrss.sherman.hawaii.edu/caldwell/caldwell.htm


Caldwell, R.M., and J.W. Hansen.


CropSys (Crop Systems) is a process-level, simulation model designed to predict the performance of multiple cropping systems across genotype, soil, weather and management combinations (Caldwell and Hansen, 1993). Use of a weather generator allows analysis of the stochastic performance of the systems. CropSys was designed by Robert Caldwell of the University of Hawaii as part of the International Benchmark Sites Network for Agrotechnology Transfer (IBSNAT) program which is partially funded by USDA-CSRS. CropSys is a high-level modeling system that contains several sets of models, including several of the CERES-type models.

The models currently in CropSys include: CERES-Barley, CERES-Maize, CERES-Millet, CERES-Rice, CERES-Sorghum, and CERES-Wheat. The SOYGRO model is also part of CropSys. CropSys uses output files defined within the IBSNAT Decision Support System for Agrotechnology Transfer (DSSAT).

Model Purpose: Originally: agrotechnology transfer. More recently: hypothesis generation (i.e. identification of knowledge gaps) and training in multiple cropping and minimum data set concepts.

How Model Functions: CropSys is built on a soil model that can operate continuously for long time periods. On a daily time step, CropSys simulates the basic processes of the water balance and nitrogen balance. Crops can be planted in any sequence. Plant processes include: light interception, and photosynthesis, dry matter partitioning, phenology, root system development, and growth in canopy dimensions and leaf area. When two species share the field at the same time the model calculates competition for light and competition for water, nitrate, and ammonium by soil layer.

Author of the abstract:


II. Technical Information

II.1 Executables:

Operating System(s): DOS and OS/2
Interactive CropSys via anonymous FTP

II.2 Source-code:

Programming Language(s): FORTRAN

II.3 Manuals:

II.4 Data:

Model Input Source: Soil information is taken from basic soil survey data. Weather datacan be simulated with a weather generator; otherwise, an automated weather station is usuallyrequired to record solar radiation. Quality of Available: Since CropSys is based on the IBSNAT sole crop models, it hasbenefited from the global network of sites and scientists that have used their models. qualityhas not been an issue so far. Quantity of Available: Quantity of data is not a problem. However, a bigger data set fromlong-term studies in order to extend the use of CropSys to issues of sustainability and globalclimate change. I am currently communicating with leaders of the IGBP / GCTE programregarding modeling and studying complex agroecosystems. That work will involve long-term fieldexperimentation on intercrops. from those studies should help us shape and solidify the basicconcepts in CropSys. Other Shortfalls: is not a problem other than the lack of solar radiationmeasurements to go along with some existing field studies. The major bottleneck for CropSys isthe structure / assumptions of the single crop models used to build CropSys. The simplificationsused in those models can not be used to simulate multiple cropping systems. A new modelingapproach must be found that addresses this problem while maintaining as much compatibility aspossible.

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

Model Input Data Requirements: CropSys uses standard minimum data sets as defined byIBSNAT for the CERES models and the legume GRO models. Minimum data sets are availablefor many sets around the world.IBSNAT's minimum data set requires daily maximumtemperature. rainfall, and solar radiation. Genetic coefficients have been provided for a widerange of cultivars.

III.2.2 Output

Model Output Data:
CropSys uses the output files defined within IBSNAT's Decision SupportSystem for Agrotechnology Transfer DSSAT. These files contain yield summaries as well asthe time-course of important state variables. Programs in DSSAT are available to graph the dataand analyze the strategies.
Temporal Scale:
The basic time-step is one day. Calculation of shadow boundaries is done onsub-hourly time-steps.
Spatial Scale:
CropSys assumes a homogeneous area, using only a vertical dimension todescribe soil profile.

IV. References

Caldwell, R.M., and J.W. Hansen. 1993. Simulation of multiple cropping systems with CropSys. In SystemsApproaches to Agricultural Development. Eds. F.W.T. Penning de Vries,P. Teng, K. Metselaar. Kluwer Academic Publishers, Dordrecht, The Netherlands,pp 397-412.

V. Further information in the World-Wide-Web

VI. Additional remarks

Global change implications: This modeling system increases the relevance of crop growth models to global change research because interactions amongseveral crops may be examined. A link to a weather generator canallow a user to examine climate scenarios.

Last review of this document by: T. Gabele: 25. 6. 1997 -
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:41 CEST 2002

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