System simulation for wheat with special reference to soil and plant nitrogen dynamics and balance

ABSTRACT Akhter, S. 2005. System simulation for wheat with special reference to soil and plant nitrogen dynamics and balance. Ph.D. Dissertation. Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh. Wheat (Triticum aestivum L.) in Bangladesh is the second major cereal crop to rice and is grown under a range of management regimes with variable productivity. Assessing options of nitrogen input technology over long term weather sequence is necessary to derive appropriate strategies that can optimize and maintain high productivity of wheat over time. Wheat simulation models are proposed as tools for assessment of response to N fertilizer in order to explore potential target zones of Bangladesh for High Yielding Variety (HYV) of wheat. In the present study, the dynamic-process-based wheat simulation model, CERES (Crop Environment Resource Synthesis)-Wheat (Ritchie, 1985), contained in the Decision Support System for Agrotechnology Transfer Version 4.0 (DSSAT V4.0), was first calibrated under sub-tropical region to predict wheat yield grown with zero- and high- N (80, 120 and 160 kg ha1) under rainfed and irrigated moisture regimes in the Grey Terrace Soil (Inceptisol) at the Bangladesh Agricultural Research Institute (BARI) at Joydebpur, during 2000-01 using long-term historical weather data. Genetic Coefficients for 'Kanchan' variety wheat of was developed by altering parameters in cultivar, ecotype and species file of DSSAT v4.0. The model was then used to validate, extrapolate, and generalize the grain yields, under low-and high-N in irrigated conditions, for two other sites (Nashipur and Joydebpur) during winter of 2001-02. Long-term historical weather data were used at the target production environments to generate probabilistic estimates of wheat yield and nitrogen use efficiency. Analysis shows with high probability that under irrigated conditions and N fertilizer input 160 kg N ha would yield better for Nashipur and Joydebpur, with improved nitrogen use efficiency (NUE). The risk of crop failure with no N input was, however, substantial. Although response to N varied dramatically from year to year and site to site in association with variable weather, there appears to be no advantage in adjusting N- input strategy for the target area. The best NUE was predicted at the 80 kg N ha1 input strategy, indicating potentials of further yield increase if methods of enhancing NUE at the......