Modeling Impact of Climate Change on Fine Rice Productivity in Pakistan; An Application of Crop Models at Farmers Field.

Changing climate threatens the productivity of agriculture sector making it vulnerable both biophysically and economically. Pakistan economy is dependent upon agriculture and these climatic risks are major threats for sustainability of agricultural systems, which would be devastating not only for the socio-economic conditions of the rural population but also jeopardizing the food security. DSSAT & APSIM Models were calibrated on experimental data and validated on collected 155 farmer’s field data from five districts of Punjab. Results of experimental and farmers' farm data proved that performance of both models (APSIM and DSSAT) for rice was good. DSSAT simulated yield of 155 farms with R² (0.52), RMSE (425 kg ha^-1) and d-stat (0.78) while R² (0.42), RMSE (440 kg ha^-1) and d-stat (0.78) were calculated for APSIM. Due to changing climate, there is a reduction in rice yield differently with 30%, 20%, 13%, 7% and 6% (mean 15.2%) by DSSAT, and APSIM decreased yield 19%, 14%, 16%, 15% and 18% (mean 17.2%) using five GCMs GFDL, MPI-ESM, CCSM4, MICROC5 and Had-GEM respectively. If the current production system prevails in future, there would be about 69 to 82.6% losers for DSSAT and 72 to 76% losers in case of APSIM due to perturbed climate. Poverty rate in changing climate would be between 33 to 38% in DSSAT and from 35 to 37% in the case of APSIM. Quantification of climate change impact on future agricultural production systems depicted that there would be 57 to 70% losers in case of DSSAT and 60 to 71% losers for APSIM and poverty would be from 16.6 to 19% for DSSAT and 18 to19.2% for APSIM. To achieve high productivity and meet the need of growing population, it would be required to increase the sowing density up to 15% for rice and fertilizer use up to 15% was considered as one of the adaptation strategy to make up the soil fertility status and high fertilizer requirement of new varieties.