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United States Department of Agriculture

Agricultural Research Service

Title: Simulating landscape catena effects in no-till dryland agroecosystems using GPFARM

Authors
item Ascough, James
item Andales, Allan - COLORADO STATE UNIVERSITY
item Sherrod, Lucretia
item McMaster, Gregory
item Hansen, Neil - COLORADO STATE UNIVERSITY
item Dejonge, Kendall -
item Fathelrahman, Eihab
item Ahuja, Lajpat
item Peterson, Gary -
item Hoag, Dana -

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 22, 2010
Publication Date: October 1, 2010
Citation: Ascough II, J.C., Andales, A.A., Sherrod, L.A., Mcmaster, G.S., Hansen, N.C., DeJonge, K.C., Fathelrahman, E.M., Ahuja, L.R., Peterson, G.A., Hoag, D.L. 2010. Simulating landscape catena effects in no-till dryland agroecosystems using GPFARM. Agricultural Systems. 103(8): 569-584.

Interpretive Summary: GPFARM is a farm/ranch decision support system (DSS) designed to assist in strategic management planning for land units from the field to the whole-farm level. This study evaluated the site-specific applicability and efficacy of GPFARM based on simulation model performance for dry mass grain yield, total soil profile water content, crop residue, and total soil profile residual NO3-N across a landscape catena for dryland no-till experimental sites (Sterling, Stratton, and Walsh) in eastern Colorado. Relative error (RE) of simulated mean, normalized objective function (NOF, calculated as root mean square error RMSE divided by the observed mean), and index of agreement (d) model evaluation statistics were calculated to compare modeled results to measured data. A one-way, fixed-effect ANOVA was also performed to determine differences among experimental locations and landscape positions. GPFARM simulated versus observed REs across landscape positions ranged from -0.4% to 24.3% for crop yield, 18.8% to 39.5% for crop residue,0.8% to 17.0% for total soil profile water content, and -23.5% to -36.7% for total soil profile residual NO3-N. For trend analysis (magnitudes and landscape position differences), GPFARM simulations agreed very well with observed trends and showed that the model was able to simulate both location and landscape position differences for the majority of model output responses. GPFARM simulation results suitably demonstrate the model’s efficacy in quantifying long-term interactions (i.e., strategic planning) between the environment and alternative crop management systems across a landscape catena.

Technical Abstract: Alternative agricultural management systems in the semi-arid Great Plains are receiving increasing attention. GPFARM is a farm/ranch decision support system (DSS) designed to assist in strategic management planning for land units from the field to the whole-farm level. This study evaluated the site-specific applicability and efficacy of GPFARM based on simulation model performance for dry mass grain yield, total soil profile water content, crop residue, and total soil profile residual NO3-N across a landscape catena for dryland no-till experimental sites in eastern Colorado. Field data were collected from 1987 through 1999 from an on-going, long-term experiment at three locations in eastern Colorado along a gradient of low (Sterling), medium (Stratton), and high (Walsh) potential evapotranspiration. Simulated crop alternatives were winter wheat (Triticum aestivum L.), corn (Zea mays L.), sorghum (Sorghum bicolor L.), proso millet (Panicum miliaceum L.), and fallow. Relative error (RE) of simulated mean, normalized objective function (NOF, calculated as root mean square error RMSE divided by the observed mean), and index of agreement (d) model evaluation statistics were calculated to compare modeled results to measured data. A one-way, fixed-effect ANOVA was also performed to determine differences among experimental locations and landscape positions. GPFARM simulated versus observed REs across landscape positions ranged from -0.4% to 24.3% for crop yield, 18.8% to 39.5% for crop residue,0.8% to 17.0% for total soil profile water content, and -23.5% to -36.7% for total soil profile residual NO3-N. For trend analysis (magnitudes and landscape position differences), GPFARM simulations agreed very well with observed trends and showed that the model was able to simulate both location and landscape position differences for the majority of model output responses. GPFARM simulation results suitably demonstrate the model’s efficacy in quantifying long-term interactions (i.e., strategic planning) between the environment and alternative crop management systems, but the simulation model may be lacking in accuracy for predictions on a short-term (tactical) planning basis. It is anticipated that improvements in the crop growth and environmental components (including improved parameterization) of the GPFARM simulation model will improve its accuracy for both strategic and tactical applications across a landscape catena.

Last Modified: 4/19/2014