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Title:   Author  item
                                            FANG, Q - Qingdao Agricultural Universityitem
                                            Ma, Liwangitem
                                            Trout, Thomasitem
                                            Comas, Louiseitem
                                            DeJonge, Kendallitem
                                            Ahuja, Lajpatitem
                                            Sherrod, Lucretiaitem
                                            Malone, Robert

                                                         - *Rob*
  Submitted to: Transactions of the ASABE
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 10/17/2017
                                    Publication  Date: 12/1/2017
                                    Citation: Fang, Q.X., Ma, L., Trout, T.J., Comas, L.H., Dejonge, K.C., Ahuja, L.R., Sherrod, L.A., Malone, R.W. 2017. Modeling N concentration and uptake for maize hybrids under growth stage-based deficit irrigations. Transactions of the ASABE. 60:2067-2081. doi:org/10.13031/trans.12405.DOI: https://doi.org/10.13031/trans.12405                                                              
                                Interpretive Summary: Modern maize cultivars have lower aboveground and grain N concentration than old cultivars 30 years ago, which requires modification of the methods used to calculate crop N demand in crop models.  The objective of this study was to evaluate the CERES-Maize in the Root Zone Water Quality Model (RZWQM2) with new algorithms of calculating critical N concentration in aboveground biomass and grain. Experimental data were acquired in 2012 and 2013 in Greeley, Colorado, where maize was irrigated to meet certain water requirement at both vegetative and maturation stages.   The original model showed little or no response of aboveground and grain N concentration to the irrigation treatments. The modified model, on the other hand, significantly improved aboveground and grain N concentration simulation, and responded to the irrigation treatments. The new algorithms, however, did not result in better simulation of N uptake, mainly due to less accurate simulation of aboveground biomass and grain yield in response to growth-stage based irrigation treatments. These algorithms for calculating critical N concentrations in CERES-Maize need to be tested further under different water stress conditions, especially after the model is improved for its simulation of biomass and yield under growth-stage based irrigation.
                                Technical Abstract: Recent research has shown a decrease in the critical aboveground biomass (AGB) nitrogen (N) concentration (Ncr) and grain N concentration (GNC) in modern maize hybrids. However, this new knowledge has not yet been incorporated into crop models that were generally developed based on previous hybrids. The objective of this study was to evaluate the CERES-Maize in the Root Zone Water Quality Model (RZWQM2) with new algorithms of calculating Ncr and GNC for modern maize cultivars in the literature. Maize was irrigated to meet certain water requirement at both vegetative and maturation stages in 2012 and 2013 in Greeley, Colorado.   The original model showed little or no response of aboveground and grain N concentration to the irrigation treatments. The modified model, on the other hand, significantly improved aboveground and grain N concentration simulation, and responded to the irrigation treatments with much lower root mean square error (RMSE) values and higher R2 values in the two years. The new algorithms, however, did not result in better simulation of N uptake, mainly due to less accurate simulation of aboveground biomass and grain yield in response to growth-stage based irrigation treatments. These algorithms for calculating critical N concentrations in CERES-Maize need to be tested further under different water stress conditions, especially after the model is improved for its simulation of biomass and yield under growth-stage based irrigation.


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