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Title: MODELING NITROGEN MANAGEMENT EFFECTS ON WINTER WHEAT PRODUCTION USING RZWQM AND CERES-WHEAT

Author
item SA, SASEENDRAN - COLORADO STATE UNIV
item Nielsen, David
item Ma, Liwang
item Ahuja, Lajpat
item Halvorson, Ardell

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2003
Publication Date: 11/17/2003
Citation: Saseendran, S.A., Nielsen, D.C., Ma, L., Ahuja, L.R., Halvorson, A.D. 2003. Modeling nitrogen management effects on winter wheat production using RZWQM and CERES-Wheat. Agronomy Journal 96:615-630.

Interpretive Summary: Agricultural system models can save the time and expense of field studies necessary to determine the nitrogen requirement for winter wheat production under the widely varying available water conditions of the central Great Plains. Two models (Root Zone Water Quality Model, RZWQM; CERES-wheat, a part of the Decision Support System for Agrotechnology Transfer) were parameterized and calibrated with three years of data from wheat grown with five levels of nitrogen fertilizer application at Akron, CO. Both models predicted yield and biomass adequately. Long-term simulations using historical weather data indicated that an N application rate of 56 kg/ha generally maximized yield while minimizing N leaching and residual soil N at harvest. Model results also showed that the wheat-fallow system is less water use efficient, but more N use efficient, than a continuous wheat system under rainfed conditions in eastern Colorado.

Technical Abstract: Agricultural system models are a less time-consuming and less expensive means than field studies of determining the nitrogen (N) requirement of crops for increased production with minimum impact on water quality under varied soil and climatic conditions. In this context, we parameterized the Root Zone Water Quality Model (RZWQM) for winter wheat (Triticum aestivum L.) simulation and then evaluated it along with the CERES-wheat model to assess their potential for N management in the semiarid climate of eastern Colorado. Both models were evaluated with data from five N treatments (0, 28, 56, 84, and 112 kg N/ha) and 3 crop seasons (87-88, 88-89, 89-90). Data from 1987-88, 0 N treatment was used for model calibration; the rest of the data were used for model validation. Genetic coefficients for winter wheat (cv. TAM 107) were developed for the CERES-wheat model. Crop parameter values required for the generic crop model of RZWQM were determined using information from the literature or by calibration. Both models were calibrated first for soil moisture and then for biomass and grain yield. RZWQM more closely predicted soil water contents for the validation data sets than CERES-wheat. Grain yield and above ground biomass were predicted well by both models. Long term simulations by both models using historical weather data (1912 through 2001) showed that 56 kg/ha N applied as broadcast incorporated (0 to 10 cm depth) in split doses of 50% at planting followed by 25% each fortnightly is a viable N management option in eastern Colorado (evaluation based on grain yield, crop N uptake, N leaching into ground water and residual soil N at harvest). Model simulations also showed that wheat-fallow is less water use efficient but more N use efficient than continuous wheat under rainfed agriculture in eastern Colorado.