Multi-Model Evaluation and Climate Change Impact Assessment with Farmers' Surveyed Data in Wheat.

Wheat productivity in relation to food security is extremely vulnerable to climate change globally in general and arid to semi-arid in particular farmers field in Pakistan. Climate change hazards would be more devastating in future because there would be 2.8 °C rise in maximum and 2.2 °C in minimum temperature for mid-century (2040-2069) in Rice-Wheat (RW) cropping system. The main thrust of this study is to develop adaptation strategies through crop growth models (DSSAT and APSIM) to counter the effects of climate change on farmers’ field and improving livelihood in the hotspot and disseminate information to the stakeholders. Crop growth models were calibrated and evaluated on experimental field data to develop the robust genetic coefficients. Models were firstly calibrated with experimental data and then validated using farmers’ field (155) data of five districts in RW cropping system in Punjab, Pakistan. A close agreement was observed between farmer and simulated yield. When models were validated at farmers’ field, goodness of model (R²) with values of 0.64 was recorded in DSSAT and 0.37 for APSIM between observed and simulated yield of 155 farms. Comparison of individual farmer yield showed that models simulated wheat yield with percent difference (PD) ranging from -25 to 17% and -26 to 40% having Root Mean Square Error (RMSE) 436 kg ha^-1 and 592 kg ha^-1 with d-index (0.87 and 0.72) for DSSAT and APSIM, respectively. DSSAT farmers’ field results were good comparative to APSIM. Climate change impact was quantified with crop models using baseline (1981-2010) and future climate data of five General Circulation Models (CCSM4, GFDL, HadGEM, MIROC5, and MPI-ESM) for mid-century (2040-2069). Mean yield reduction for DSSAT ranged between 6.2 to 19 % while for APSIM yield reduction was 10.6 to 12.3 % with five GCMs. Adaptation technology was developed to cope with the drastic impacts of changing climate. To achieve high productivity and meet the need of growing population, it would be required to increase the planting density and fertilizer use up to 30% and 25%, respectively which was considered as one of the adaptation strategy for promising cultivars with 50% greater potential. Due to high temperature the cropping seasons will be affected and 15 days earlier planting over current would be recommended. These strategies have a significant impact in reducing the vulnerabilities of the changing climate with 22% improvement in wheat yield to sustain food security in Rice-wheat cropping system.