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United States Department of Agriculture

Agricultural Research Service


item Ma, Liwang
item Hoogenboom, Gerrit
item Ahuja, Lajpat
item Nielsen, David
item Ascough Ii, James

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2005
Publication Date: 7/13/2005
Citation: Ma, L., Hoogenboom, G., Ahuja, L.R., Nielsen, D.C., Ascough II, J.C. 2005.Development and evaluation of the RZWQM-CROPGRO hybrid model for soybean production. Agronomy Journal. 97:1172-1182.

Interpretive Summary: Computer simulation models developed for agricultural applications have simulated processes differently based on the problems they were designed to solve. The Root Zone Water Quality Model (RZWQM) emphasizes water and soil quality while employing a non-detailed generic crop growth component. The CROPGRO model has a more detailed crop model (simulating yield components and phenology), with less attention given to soil processes. This study reports comparisons of results from a hybrid model in which the crop production model from CROPGRO is used within the RZWQM in place of its generic crop growth component and results from the original CROPGRO model. Very few differences were noted between the results from the original and hybrid models. Therefore, the hybrid model will allow users the opportunity for generating detailed crop development results while also obtaining detailed soil and water quality results.

Technical Abstract: It is a common practice for agricultural system modelers to develop or enhance their models by incorporating or combining existing modules from other models to improve the functionality of certain model components. In this study, the CROPGRO plant growth model from DSSAT (Decision Support System for Agrotechnology Transfer) was linked to the Root Zone Water Quality Model (RZWQM) to improve crop production simulation in RZWQM. In the hybrid model, RZWQM provided CROPGRO with daily soil water and soil nitrogen (N), and potential evapotranspiration (PET), whereas CROPGRO fed back to RZWQM with root distribution, leaf area index, and other plant growth and development variables as needed. The RZWQM-CROPGRO hybrid model was then evaluated against the original DSSAT-CROPGRO model using several datasets from the literature. These testing datasets represented various drought conditions and had various levels of detail in data collection. Results showed that the RZWQM-CROPGRO hybrid model simulated higher water stress than the original DSSAT-CROPGRO model because of high potential evapotranspiration (PET) simulated by RZWQM. Therefore, it was necessary to modify some of the cultivar coefficients originally calibrated for the DSSAT-CROPGRO model. Although, based on the F-test and paired t-test, there was no overall or consistent significant difference between the simulated outputs of RZWQM-CROPGRO and DSSAT-CROPGRO models, the RZWQM-CROPGRO hybrid model did improve responses of soybean production to water treatments under certain conditions. Therefore, this hybrid model may be used as a surrogate for RZWQM users to conduct detailed simulation of crop production in addition to addressing water quality concerns.

Last Modified: 09/19/2017
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