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Title: Modeling N concentration and uptake for maize hybrids under growth stage-based deficit irrigations

Author
item FANG, Q - Qingdao Agricultural University
item Ma, Liwang
item Trout, Thomas
item Comas, Louise
item DeJonge, Kendall
item Ahuja, Lajpat
item Sherrod, Lucretia
item 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.