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Evaluating Nitrogen and Water Management in a Double-Cropping System Using RZWQM

^a Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences
^b USDA-ARS Great Plains Systems Research Unit, Fort Collins, CO 80526

View larger version (36K): [in a new window]   Fig. 1. Comparison between model-predicted and field-measured soil water contents at various soil depths for the 200 kg N ha–1 yr–1 treatment (model calibration). Values in parentheses are root mean squared errors of soil water predictions (m3 m–3).

View larger version (21K): [in a new window]   Fig. 2. Comparison between the model-predicted and field-measured soil profile (180-cm) water storage: (a) calibration results for the 200 kg N ha–1 yr–1 treatment (WC200N) during 2001 to 2003; (b) validation results for 400, 600, and 800 kg N ha–1 yr–1 (WC400N, WC600N, and WC800N, respectively) during 2001 to 2003. Numbers in parentheses are corresponding root mean squared errors.

View larger version (22K): [in a new window]   Fig. 3. Comparison between model-predicted and field-measured soil profile (180-cm) water contents for the 400 kg N ha–1 yr–1 treatment (other N rates have similar trends, not shown).

View larger version (40K): [in a new window]   Fig. 4. Comparison between model-predicted and field-measured soil water contents at various soil depths for the 400 kg N ha–1 yr–1 treatment (other N rates have similar trends, not shown). Values in parentheses are root mean squared errors.

View larger version (21K): [in a new window]   Fig. 5. Comparison between model-predicted and measured grain yields for the 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments during 2001 to 2003. Error bars represent ± one standard deviation of the measured grain yield from the mean of replications.

View larger version (24K): [in a new window]   Fig. 6. Comparison between model-predicted and measured aboveground biomass for the 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments during 2001 to 2003. Error bars represent ± one standard deviation of the measured aboveground biomass from the mean of replications.

View larger version (21K): [in a new window]   Fig. 7. Comparison between the model-predicted and measured aboveground biomass N uptake for the 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments during 2001 to 2003. Error bars represent ± one standard deviation of the measured aboveground biomass N uptake from the mean of replications.

View larger version (21K): [in a new window]   Fig. 8. Comparison between the model-predicted and measured grain N uptake for the 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments during 2001 to 2003. Error bars represent ± one standard deviation of the measured grain N uptake from the mean of replications.

View larger version (22K): [in a new window]   Fig. 9. Comparison between the model-predicted and measured soil residual NO3–N (0–180 cm) at harvest of the crops for the 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments during 2001 to 2003. Error bars represent ± one standard deviation of the measured soil residual NO3–N from the mean of replications.

View larger version (34K): [in a new window]   Fig. 10. The RZWQM-predicted N losses due to denitrification, volatilization, and deep seepage per crop season in the wheat–corn double cropping system under 200, 400, 600, and 800 kg N ha–1 yr–1 (WC200N, WC400N, WC600N, and WC800N, respectively) treatments.