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Title: Enhancing the water stress factors for simulation of corn (Zea mays L.) in RZWQM2

Author
item ANAPALLI, SASEENDRAN - Colorado State University
item Ahuja, Lajpat
item Ma, Liwang
item Nielsen, David
item Trout, Thomas
item ANDALES, ALLAN - Colorado State University
item CHAVEZ, JOSE - Colorado State University
item HAM, JAY - Colorado State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2013
Publication Date: 9/16/2013
Citation: Anapalli, S.S., Ahuja, L.R., Ma, L., Nielsen, D.C., Trout, T.J., Andales, A.A., Chavez, J.L., Ham, J. 2013. Enhancing the water stress factors for simulation of corn (Zea mays L.) in RZWQM2. Agronomy Journal. 10:2134.

Interpretive Summary: Declining irrigation water supply is the major limiting factor for corn production in the world today. In this context, agricultural system models are state of the science tools for developing crop and water management practices for optimized use of limited precipitation and supplementary irrigation for crop production. Accurate quantification of crop responses to water stress in agricultural system models is critical for their applications for this purpose. The RZWQM2 model uses the DSSAT v4.0 (CSM-CERES and CROPGRO) crop models for simulations of various crops and uses its water stress functions. In this study, we modified the current DSSAT-CSM stress factors in the RZWQM2 in two different ways as modifications of the current water stress factors in the model and using the daily potential root water uptake (TRWUP) calculated by Nimah and Hanks (1973) approach. The modified model gave reasonable simulations of the detailed multi-level irrigation experiments in corn from 2008 to 2011 at Greeley, CO; dryland and limited irrigation studies at Akron, CO; and an experiment in a sandy soil at Gainesville, Florida available in DSSAT 4.5 database.

Technical Abstract: Enhancement of agricultural system models for more accurate simulations of water stress responses of crops can improve their applications in limited water management. Currently, the crop system model RZWQM2 use a ratio of potential root water uptake (supply) to potential transpiration (demand) as a water stress factor (WSDef) that modulates plant growth processes. We tested two progressive modifications of the WSDef (WSI1 and WSI2) in the DSSAT-CSM-CERES-Maize (v 4.0) module embedded within the RZWQM2 model for simulating response of corn to different levels of water and compared with the use of WSDef. WSI1 was a modification of SWFAC factor for photosynthesis related processes in RZWQM2 using the daily potential root water uptake (TRWUP) calculated by Nimah and Hanks (1973) approach, and WSI2 was with accounting for stress due to additional heating of canopy from unused energy of potential soil evaporation in both the supply and demand terms of the WSI1. These factors were evaluated on the data for corn grain yield, biomass, soil water and LAI derived from canopy cover data from multiple water-level experiments conducted at Greeley, Colorado from 2008 to 2011; irrigated and rainfed corn at Akron, Colorado; and irrigated corn at Gainesville, Florida, on different soil types. The stress factors, WSI1 and WSI2 were found to be superior to WSDef in simulations of grain yield, biomass and LAI in all the above three experiments. Further, in general, WSI2 simulations of the crop were either comparable or more accurate than WSI1 simulations in most of the crop seasons simulated in this study. Options for simulating corn using WSDef, WSI1 or WSI2 will be available in the future public release versions of RZWQM2.