Evaluation of the CERES-Maize water and nitrogen balances under tile-drained conditions$

The CERES-Maize model was developed to investigate how variations in environmental conditions, management decisions, and genetics interact to a€ect crop development and growth. A tile drainage subroutine was incorporated into CERES-Maize to improve soil-water and nitrogen leaching under subsurface tile drainage conditions. The purpose of this work was to evaluate the soil-water, soil-nitrogen, tile drainage, and tile-nitrogen loss routines of CERES-Maize for tile-drained ®elds in Iowa. An analysis was conducted based on information collected from a study of 36 plots consisting of ®ve management systems during a 4-year period from 1993 to 1996, at Nashua, IA. The model was calibrated for each plot using data from 1994 and 1995, and validated using data from 1993 and 1996. Temporal soil-water contents and water ̄ow from tile drains were calibrated to an average root mean square error (RMSE) of 0.036 cm cmÿ3 and 2.62 cm, respectively, compared to measured values. Validation trials gave an average RMSE for soil-water and tile drainage of 0.046 cm cmÿ3 and 5.3 cm, respectively. Soil-nitrate and tile-nitrogen ̄ows were calibrated, with an RMSE of 6.27 mg NO3 gÿ1 soilÿ1 and 3.21 kg N haÿ1 soilÿ1, respectively. For the validation trials, the RMSE for soil-nitrate content and cumulative tile-nitrate ̄ow was 6.82 mg NO3 gÿ1 soilÿ1 and 8.8 kg N haÿ1, respectively. These results indicate that the new tile drainage algorithms describe water and nitrate movement reasonably well, which will improve the performance of CERES-Maize for arti®cially drained ®elds. # 2000 Elsevier Science Ltd. All rights reserved.