GPFARM Evaluation Across a No-Till Dryland Agroecosystem Landscape Catina.
James C. Ascough II1, Allan A. Andales1, Gregory S. McMaster1, and Neil Hansen2. (1) USDA-ARS, ASRU, 2150 Centre Ave., Bldg. D, Suite 200, Fort Collins, CO 80526, (2) Colorado State Univ, Dept of Soil & Crop Science (1170), Ft. Collins, CO 80523-1170
GPFARM is a USDA-ARS
decision support system (DSS) for strategic (long-term) planning. This study evaluated GPFARM performance for
comparing alternative dryland no-till cropping
systems and established limits of accuracy for eastern Colorado locations. Data used in the GPFARM evaluation were
collected in 1987 through 1999 from an on-going long-term experiment at three
locations along: 1) a gradient of potential evapotranspiration
(PET) [Sterling, low PET; Stratton, medium PET; and Walsh, high PET]; and 2)
across summit, sideslope, and toeslope
landscape positions at all three sites.
Crops included winter wheat (W) [Triticumaestivum (L.)], corn (C) [Zeamays (L.)], sorghum (S) [Sorghum bicolor (L.) Moench],
proso millet (M) [Panicummiliaceum(L.)],
and varying fallow (F) periods; crop rotations included WF, WCF, WCMF, WSF, and
WSMF. Ranges of relative error (RE) of
simulated mean and root mean square error (RMSE) were calculated for total soil
profile water content, dry mass grain yield, dry mass crop residue, and total
soil profile residual nitrate-N. GPFARM simulations agreed with observed trends
and showed that productivity and water use efficiency increased with cropping
intensification and downslope landscape position.