Calibration and validation of CERES-wheat model for North Western Himalayas

A field experiment was conducted during rabi season 2015-16 and 2016-17 comprising four wheat varieties (viz., HS-490, VL-829, VL-892 and VL-907) grown on five different sowing dates (viz., 20th October, 5th November, 20th November, 5th December and 20th December) in split plot design with three replications at Department of Agronomy, Forages and Grassland Management farm, CSK HPKV, Palampur, Himachal Pradesh (India). The DSSAT-CERES-wheat (version 4.6) model was calibrated using various growth and yield parametrs collected from experiment conducted during 2015-16 while for validation, data collected from subsequent experiment (2016-17) have been used. The results of the present investigation revealed that among different treatments during 2015-16, the range of the observed and simulated yield was 3.3-5 t ha(-1) and 3.0-5.4 t ha(-1), respectively whereas during 2016-17, it was 2.6-3.8 t ha(-1) (observed) and 2.9-3.9 t ha(-1) (simulated). The mean observed and simulated grain yield was 3.1 to 3.9 t ha(-1) and 3.2 to 3.9 t ha(-1). For observed and simulated grain yield, standard deviation (SD) of 496 and 601 kg and coefficient of variation (CV) of 13 and 15 % has been recorded during 2015-16 while during 2016-17, it was 441 and 247 kg (SD) and 13 and 8 % (CV). Likewise, observed and simulated above ground biomass was 8.3-12.4 t ha(-1) and 8.2-12.9 t ha(-1) during 2015-16 and 6.5-12.0 t ha(-1) and 6.0-11.9 t ha(-1) 2016-17, respectively. Among the treatments, mean simulated biological yield was 10.2 and 7.9 t ha(-1) while, observed was 9.9 and 8.3 t ha(-1). For observed and simulated biomass production, 1303 and 1507 kg SD and 13 and 15 % CV was recorded during 2015-16 but during 2016-17, it was 1670 and 1873 (SD) and 20 and 24 % (CV), respectively. During both the years, between observed and simulating grain yield, high correlation coefficient (r = 0.76 & 0.85), low RMSE (381 & 281 kg), nRMSE (9.6 & 8.9 %), MBE (-0.5 & 77.3 kg) and MAPE (0.06 & 3.5 %) confirmed the accurate simulation by model. High simulated and observed grain yield was obtained if variety HS-490 (2015-16) and VL-907 (2016-17) were sown on 20th November. Similarly, for observed and simulated biomass production high correlation coefficient, (r = 0.89 and 0.98) and low RMSE (735 and 591 kg), nRMSE (7.4 and 7.0 %), MBE (316 and 453 kg) and MAPE (3.2 and -5.9 %), have been recorded, among the treatments. Thus, the grain yield and above ground biomass of wheat cultivars were fairly simulated by the DSSAT model hence, it may be used for crop yield simulations under varying input conditions of mid hill region of Himachal Pradesh.