Detection of abiotic stresses in wheat (Triticum aestivum L.) using crop simulation model and aerial photography in Tarai region of Uttarakhand
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
A field experiment was conducted at Norman E. Borlaug Crop Research Centre, Pantnagar (Uttarakhand) during Rabi season of 2017-18 to study the response of late sown (December) and very late sown wheat crop (January) to different irrigation and nitrogen management practices in order to understand the effect of stress condition on wheat yield and its parameters by using CSM-CROPSIM-CERES-wheat model, infrared thermometer, and aerial photography. Twenty seven treatments consisted of three dates of sowing (12th December, 22nd December and 02nd January), three levels of irrigation (100% irrigations, 75% irrigations and 50% irrigations) and three levels of nitrogen (100%, 75% and 50% of recommended nitrogen doses). The experiment was laid in a Factorial Randomized Block Design (R.B.D.) with three replications. The results revealed that the genetic coefficients derived from calibration of the CSM-CROPSIM-CERESWheat model under different treatment combinations showed reasonably good agreement between simulated and measured data of crop phenology, LAI and grain yield. For the above described treatment combinations, the calibrated model with wheat variety PBW-502, simulated wheat yield with root mean square error (RMSE) of 11.61%. Sensitivity of model was analysed for weather (temperature, solar radiation) and non –weather parameters (nitrogen and irrigation) under optimal condition. The results showed that grain yields as simulated by the model due to alteration of ambient temperature in incremental units showed a gradual decrease in yield, while decreasing (- 1 to -3°C) ambient temperature led to the increase in wheat yield by 9 to 26 %. Increase in daily solar radiation (1 to 3 MJm-2), resulted into nearly 2 to 12 % increase in yield over the base yield under optimal condition. This showed that the model was less sensitive to solar radiation than it was to temperature. Likewise, variation in irrigation and nitrogen showed variation in wheat yield. Canopy temperature was measured on 22nd Feb, 9th March and 24th March. Stress degree days (Tc-Ta) and subsequently accumulated stress degree days for whole growing season were calculated. These measurements were made to determine the occurrence and severity of water stress resulting from different water treatments and to evaluate the influence of nitrogen (N) fertilization on canopy temperature. With decrease in irrigation and nitrogen application, canopy temperature increased by 5.310C to 8.710C and 5.95 to 7.920C, respectively. Increase in irrigation and nitrogen levels has lowered the SDD, indicating a better canopy thermal environment under higher irrigation and nitrogen application. The significantly linear and negative relationship has obtained with canopy temperature and grain yield as well as SDD and grain yield. Low altitude aerial photography presents an exciting opportunity to monitor crop field with high spatial and temporal resolution in order to monitor water and nutrient stresses in the area of study. NDVI was estimated by image processing and regression analysis revealed a linear and positive one to one relationship with grain yield. Yield losses were calculated by evaluating the difference between simulated and observed yield which was positively related with accumulated stress degree days and negatively with NDVI. On the basis of experience gained in the present study, it can be concluded that an integration approach (crop simulation model, low altitude photography and canopy temperature) can be efficiently used with reasonably higher accuracy for assessing the yield losses in real time. The real-time yield loss assessment will prove to be crucial for disbursing agricultural insurance claims under Pradhan-Mantri Fasal Beema Yojna and such other schemes.
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