Mahdi, S. SherazSar, Koushik2017-07-242017-07-242017-07http://krishikosh.egranth.ac.in/handle/1/5810026026Crop growth simulation models are useful tools for considering the complex interactions between a range of factors that affect crop performance, including weather, soil properties and crop management. Crop Environment Resource Synthesis (CERES)- Wheat DSSAT v4.6 model was used to simulate responses of wheat varieties with various sowing environments. In this context, an experiments during the year 2015-16 and 2016-17 on two sowing dates (November 23, December 15) and three varieties (cv. HD2733, GW322 and K307) with four replications was conducted at the wheat section, Research Farm, Bihar Agricultural University, Sabour, Bhagalpur. As an input data for DSSAT model, layer wise soil data was generated and climate data was collected from meteorological observatory, Sabour. Crop management and experimental data was measured from the experimental field. Results revealed that irrespective of variety, timely sown wheat (D1) registered significantly higher grain yield over the two years of study than the wheat crop sown under late conditions (D2). The pooled yield over two years also followed a similar trend. Crop sown on DI recorded a grain yield increase of 15.91 per cent over crop yield sown at D2. The interaction effect between date of sowing and varieties was found to be significant. The treatment combination (D1V1) recorded significantly highest grain yield (47.5 and 48.3 q ha-1) over rest of the treatment combinations and next in order was D1V2 treatment combination with grain yield of 43.7 and 44.4 q ha-1 during both the years of experimentation and pooled of the years. The lowest yield reduction of 13.35 % was recorded in V1 while the maximum yield reduction of 17.30% was recorded in V3 for D2 sowing. Model outputs viz., simulated growth and development (anthesis, physiological maturity, maximum leaf area index and grain yield) were close to observed and measured parameters for both the years of study. The root mean square error (RMSE) values ranged from 2.70-2.97, 0.34-0.36, 2.34-3.08 and 318-343 for anthesis, LAI, physiological maturity and grain yield respectively. D-index, R2 and error percentage values were also in acceptable range between simulated and observed values for different phenophases, LAI and grain yield during both years of study. Based on these results it can be concluded that the model was very robust in predicting the critical phenological growth stages and yield of different cultivars of wheat under different sowing environment. To calibrate and validate the model, it is necessary to determine the genetic coefficients of each wheat genotype used in the study. Therefore, for development of genetic coefficients, all the genotypes were entered into the CUL file extension. Seven genetic coefficients were considered of which three were related to crop development (P1V, P1D, and P5), three to growth (G1, G2, and G3), and one called phyllochron (PHINT) that involves the thermal time requirement for leaf appearance. These coefficients establish the genetic differences among cultivars and give an idea about the duration of the growth cycle and harvest index of each one. It can be concluded from the obtained results that the genetic coefficients derived from the calibration of the CERES Wheat DSSAT v4.6 model for three varieties (HD2733, GW322 and K307) under two dates of sowing (November, 23 and December, 15) showed reasonably very good agreement between simulated crop phenology, LAI and grain yield with experimental measured data. The RMSE, R2 and D-values showed the accuracy of genetic coefficient better fit to project future wheat yield levels. The wheat cultivar "HD2733" sown on 23 November, took longer duration for attaining different phenophases and recorded the maximum yield over two years and pooled. However, the similar set of experiment should be conducted at different locations of Bihar for further confirmation of present study.ennullThesis