ABSTRACT: The rice-wheat farming system in Punjab, Pakistan, faces significant threats from climate change, including rising temperatures, extreme rainfall, and water...
The rice-wheat farming system in Punjab, Pakistan, faces significant threats from climate change, including rising temperatures, extreme rainfall, and water shortages due to glacial melt. By 2050, temperatures in Punjab are projected to increase by 2°C, causing seasonal shifts with heavier wet-season rainfall and drier dry seasons, which could intensify flooding and droughts. This poses a risk to food security, as yields of essential crops like rice, wheat, and cotton plateau, potentially reducing rice yields by 8-30% and wheat by 6-19%, increasing poverty by 6%. To mitigate these impacts, a study by local researchers under AgMIP assessed adaptation strategies such as early sowing, improved crop varieties, increased sowing density, and enhanced fertilizer use. These measures could substantially reduce projected poverty rates and support resilience in small-holder farming, emphasizing the need for collaborative efforts to sustain food security in the face of climate challenges. The study focuses on the calibration and evaluation of the DSSAT crop models for various crops (wheat, rice, maize, and cotton) using field experiment data to predict crop growth and productivity under local climatic conditions. The models were parameterized with crop-specific data, including growth stages, soil, and weather conditions. The study also assessed the impact of different agronomic practices and nitrogen levels on crop yield using simulations from the DSSAT platform. Additionally, future climate scenarios based on the HAPPI project were statistically downscaled to predict temperature and rainfall changes, showing significant warming and altered rainfall patterns, which were then incorporated into the DSSAT models to assess climate change impacts on crop yields. The study focuses on calibrating and evaluating the CSM-CERES-Wheat model for wheat cultivars Faisalabad-2008, Lasani-2008, and Sahar-2006 under varying nitrogen treatments in Faisalabad, Pakistan. The model accurately predicted phenology, leaf area index (LAI), and grain yield, with minimal errors in simulated versus observed data, particularly for anthesis and maturity dates. However, discrepancies were noted in the model's response to different nitrogen levels, as it did not account for nitrogen-induced delays in anthesis and maturity. Despite this, the model performed well for grain yield prediction, with the best results for Sahar-2006. The calibration process involved estimating genetic coefficients, which were found to be robust, allowing the model to simulate growth and yield effectively under irrigated, semi-arid conditions. Overall, the model is suitable for predicting wheat growth and yield, guiding agronomic practices in similar environments. The calibration of the CERES-Maize model for three maize hybrids (Pioneer-1543, Monsanto-DK6103, and Syngenta-NK8711) focused on phenological and growth parameters, including thermal time, kernel growth, and leaf area index (LAI). Monsanto-DK6103 required more thermal time from seedling emergence to juvenile phase (P1) and from silking to maturity (P5) compared to the other hybrids, while Syngenta-NK8711 was a shorter duration cultivar. The model showed good predictions for phenology, growth, and grain yield, with the best fit observed in the long-duration hybrids, Monsanto-DK6103 and Pioneer-1543, which also exhibited higher grain yields. However, slight under simulations were noted, particularly in leaf area index (LAI) and biomass, but the model's performance was generally deemed acceptable. The simulations indicated that early sowing dates yielded the highest grain production, especially for longer-duration hybrids, highlighting the model's ability to predict the impact of planting date on yield. The study explores the impact of climate change on agricultural yields in Punjab, Pakistan, focusing on rice, maize, and cotton. In rice, significant yield reductions were observed in southern districts like Bahawalpur (up to 26%), while northern regions like Sialkot experienced positive impacts with a 5.3% increase in yield. Maize showed less drastic reductions, with some districts like Bahawalpur and Sialkot seeing yield increases due to favorable soil and rainfall conditions. Cotton yields, however, were negatively affected by rising temperatures across Punjab, particularly in the south, where reductions of 18% were recorded. The study highlights the varying regional impacts and emphasizes the need for adaptation measures to mitigate the negative effects of climate change on crop production.