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Title:   Author  item
                                            Ma, Liwangitem
                                            Malone, Robert

                                                         - *Rob*item
                                            Heilman, Philip

                                                         - *Phil*item
                                            Jaynes, Danitem
                                            Ahuja, Lajpatitem
                                            SASEENDRAN, S - COLORADO STATE UNIVERSITYitem
                                            KANWAR, R - IOWA STATE UNIVERSITYitem
                                            Ascough Ii, James
  Submitted to: Geoderma
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/28/2006
                                    Publication  Date: 5/17/2007
                                    Citation: Ma, L., Malone, R.W., Heilman, P., Jaynes, D.B., Ahuja, L.R., Saseendran, S.A., Kanwar, R.S., Ascough II, J.C. 2007. RZWQM simulated effects of crop rotation, tillage, and controlled drainage on crop yield and nitrate-n loss in drain flow. Geoderma 140(3):260-271. doi:10/1016/j/geoderma.2007.04.010.Interpretive Summary: Correct simulation of agricultural management effects is vitally important for developing decision support tools through system models. In this study, the Root Zone Water Quality Model (RZWQM) was used to evaluate the long-term effects of tillage, crop rotation, and controlled drainage on crop production and N loading in drain flow in Nashua, Iowa of the US. The calibrated model correctly simulated lower observed N concentration in drain flow under NT (no-till) than under MP (moldboard plow), CP (chisel plow), and RT (ridge till) due to lower mineralization rates under NT. It also correctly simulated yearly drain flow and N loss in drain flow under these tillage practices. However, the model failed to simulate lower corn and soybean yield under NT than under MP, CP, and RT. In addition, RZWQM correctly simulated lower yearly drain flow and N loss in drain flow under CS (corn-soybean) and SC (soybean-corn) than under CC (continuous corn). The model correctly simulated higher corn yield under CS and SC than under CC. Using the newly suggested N management practice for the Midwest of controlled drainage, the model correctly simulated 30% reduction in drain flow and N losses in drain flow under controlled drainage (CD) compared to free drainage (FD). RZWQM simulated higher yearly drain flow with NT compared to MP (12-18%) and CP (4-8%) due to lower simulated evapotranspiration with NT (1-8%). The model also correctly simulated higher lateral subsurface flow (15-20%) and higher runoff (8-10%) under controlled drainage. Except for tillage effects on crop yield, the simulated management effects are in close agreement with experimental observations and demonstrate that RZWQM is a promising tool to quantifying the relatively effects of tillage, crop rotation, and controlled drainage. Therefore, a calibrated RZWQM may be used to simulate selected management effects for decision support purposes.
                                Technical Abstract: Correct simulation of agricultural management effects is vitally important for developing decision support tools through system models. In this study, the Root Zone Water Quality Model (RZWQM) was used to evaluate the long-term effects of tillage, crop rotation, and controlled drainage on crop production and N loading in drain flow in Nashua, Iowa of the US. The calibrated model correctly simulated lower observed N concentration in drain flow under NT (no-till) than under MP (moldboard plow), CP (chisel plow), and RT (ridge till) due to lower mineralization rates under NT. It also correctly simulated yearly drain flow and N loss in drain flow under these tillage practices. However, the model failed to simulate lower corn and soybean yield under NT than under MP, CP, and RT. In addition, RZWQM correctly simulated lower yearly drain flow and N loss in drain flow under CS (corn-soybean) and SC (soybean-corn) than under CC (continuous corn). The model correctly simulated higher corn yield under CS and SC than under CC. Using the newly suggested N management practice for the Midwest of controlled drainage, the model correctly simulated 30% reduction in drain flow and N losses in drain flow under controlled drainage (CD) compared to free drainage (FD). RZWQM simulated higher yearly drain flow with NT compared to MP (12-18%) and CP (4-8%) due to lower simulated evapotranspiration with NT (1-8%). The model also correctly simulated higher lateral subsurface flow (15-20%) and higher runoff (8-10%) under controlled drainage. Except for tillage effects on crop yield, the simulated management effects are in close agreement with experimental observations and demonstrate that RZWQM is a promising tool to quantifying the relatively effects of tillage, crop rotation, and controlled drainage. Therefore, a calibrated RZWQM may be used to simulate selected management effects for decision support purposes.


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