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Evaluation of GPFARM for Dryland Cropping Systems in Eastern Colorado

^a USDA-ARS Great Plains Syst. Res. Unit, P.O. Box E, Fort Collins, CO 80522
^b Dep. of Soil and Crop Sci., Colorado State Univ., Fort Collins, CO 80523

View larger version (36K): [in a new window]   Fig. 1. Schematic diagram of the GPFARM decision support system (DSS) components. Arrows indicate the flow of information.

View larger version (24K): [in a new window]   Fig. 2. Simulated grain yield and total soil profile water content against the observed values for calibration years at the toeslope position of the Sterling site. The simulated soil profile was 150 cm deep.

View larger version (37K): [in a new window]   Fig. 3. Simulated total soil profile water content against the observed values at three locations (summit position) in eastern Colorado for three rotations {wheat–fallow (WF): 1988–1999; wheat–corn (or sorghum)–fallow [WC(S)F]: 1988–1999; wheat–corn (or sorghum)–millet–fallow [WC(S)MF]: 1988–1993}. Values in parentheses are root mean square error (RMSE) (mm H2O) and d values.

View larger version (36K): [in a new window]   Fig. 4. Time series (1988–1999) of simulated and observed total soil water content at Sterling, Stratton, and Walsh for the wheat–corn (or sorghum)–fallow [WC(S)F] rotation beginning with the corn (or sorghum) phase in 1988 (Sterling and Stratton: WCF-C; Walsh: WSF-S).

View larger version (22K): [in a new window]   Fig. 5. Simulated winter wheat grain yield (dry mass) against the observed values at three locations (summit position) in eastern Colorado for three rotations {wheat–fallow (WF): 1988–1999; wheat–corn (or sorghum)–fallow [WC(S)F]: 1988–1999; wheat–corn (or sorghum)–millet–fallow [WC(S)MF]: 1988–1993}. Values in parentheses are root mean square error (RMSE) values (kg ha-1).

View larger version (44K): [in a new window]   Fig. 6. Simulated dry mass corn grain yield at (a) Sterling and (b) Stratton, simulated sorghum grain yield at (c) Walsh, and (d) simulated proso millet grain yield {wheat–corn (or sorghum)–millet–fallow [WC(S)MF] rotation only} at three locations against the observed values for two rotations {wheat–corn (or sorghum)–fallow [WC(S)F]: 1988–1999; WC(S)MF: 1988–1993}. Values in parentheses are root mean square error (RMSE) values (kg ha-1).

View larger version (51K): [in a new window]   Fig. 7. Simulated (a) dry mass surface crop residue and (b) total soil profile residual NO3–N against the observed values at three locations (summit position) in eastern Colorado for three rotations {wheat–fallow (WF): 1988–1999; wheat–corn (or sorghum)–fallow [WC(S)F]: 1988–1999; wheat–corn (or sorghum)–millet–fallow [WC(S)MF]: 1988–1993}. Values in parentheses are root mean square error (RMSE) (kg ha-1) and d values.

View larger version (50K): [in a new window]   Fig. 8. Annualized grain yields (dry mass) at three locations (1 = Sterling, 2 = Stratton, and 3 = Walsh) in three crop rotations for the period 1989 through 1993. The legend indicates location and either observed (o) or predicted (p) value (e.g., 1-p = Sterling predicted). WF, wheat–fallow (rotation); WC(S)F, wheat–corn (or sorghum)–fallow (rotation); and WC(S)MF, wheat–corn (or sorghum)–millet–fallow (rotation).

View larger version (32K): [in a new window]   Fig. 9. Grain water use efficiency (WUE) at three locations (1 = Sterling, 2 = Stratton, and 3 = Walsh) in three crop rotations for the period 1989 through 1993. The legend indicates location and either observed (o) or predicted (p) value (e.g., 1-p = Sterling predicted). WF, wheat–fallow (rotation); WC(S)F, wheat–corn (or sorghum)–fallow (rotation); and WC(S)MF, wheat–corn (or sorghum)–millet–fallow (rotation).

View larger version (39K): [in a new window]   Fig. 10. Average crop residue on the soil surface at three locations (1 = Sterling, 2 = Stratton, and 3 = Walsh) in three crop rotations for the period 1989 through 1993. The legend indicates location and either observed (o) or predicted (p) value (e.g., 1-p = Sterling predicted). WF, wheat–fallow (rotation); WC(S)F, wheat–corn (or sorghum)–fallow (rotation); and WC(S)MF, wheat–corn (or sorghum)–millet–fallow (rotation).