Agricultural System Models in Field Research and Technology Transfer

Lajpat (Laj) R. Ahuja is a supervisory soil scientist and research leader of the USDA-ARS, Great Plains Systems Research Unit, Fort Collins, Colorado. He has made original and pioneering research contributions in several areas of agricultural systems: infiltration and water flow in soils, estimation of hydraulic properties, and scaling of their spatial variability; transport of agrochemicals to runoff and to groundwater through soil matrix and macropores; quantification of the effects of tillage and other management practices on above properties and processes; and modeling of the entire agricultural systems and application of system models in field research, technology transfer, and management decision support., As development team leader, Ahuja guided the development, validation, and publication of the ARS Root Zone Water Quality Model (RZWQM), that is being widely used for evaluating effects of management on water quality and crop production. The Unit team has also developed a whole farm/ranch decision support system, GPFARM, for evaluating production, economics, and environmental impacts of alternative management systems., Ahuja has authored or co-authored more than 200 publications; he is also senior editor of the book on RZWQM. He has served as associate editor (1987 to 1992) and technical editor (1994 to 1996) of the Soil Science Society of America Journal. He is an invited guest editor of an upcoming special issue of Geoderma on “Quantifying Agricultural Management Effects on Soil Properties and Processes,” has served as advisor and consultant to several national and international organizations, and has organized several interagency/international workshops. Ahuja won the USDAARS, Southern Plains Area, Scientist of the Year Award in 1989. He was elected Fellow of the Soil Science Society of America in 1994 and the American Society of Agronomy in 1996., Liwang Ma is a soil scientist with USDA-ARS, Great Plains Systems Research Unit, Fort Collins, Colorado. Dr.

• Whole System Integration and Modeling - Essential to Agricultural Science and Technology in the 21st Century. Applications of Cotton Simulation Model, GOSSYM, for Crop Management, Economic and Policy Decisions. Experience with On-Farm Applications of GLYCIM/GUICS. Benefits of Models in Research and Decision Support: The IBSNAT Experience. Decision Support Tools for Improved Resource Management and Agricultural Sustainability. An Evaluation of RZWQM, CROPGRO, and CERES-Maize for Responses to Water Stress in the Central Great Plains of the U.S. The Co-evolution of the Agricultural Production Systems Simulator (ASPIM) and its use in Australian Dryland Cropping Research and Farm Management Intervention. Applications of Crop Growth Models in the Semi-Arid Regions. Applications of Models with Different Spatial Scale. Modeling Crop Growth and Nitrogen Dynamics for Advisory Purposes Regarding Spatial Variability. Addressing Spatial Variability in Crop Model Applications. Topographic Analysis, Scaling, and Models to Evaluate Spatial/Temporal Variability of Landscape Processes and Management. Perameterization of Agricultural System Models: Current Approaches and Future Needs. The Object Modeling System. Future Research to Fill Knowledge Gaps.