The impact of climate warming and crop management on phenology of sunflower-based cropping systems in Punjab, Pakistan

Understanding the effects of warming trends, genetics, and management on crop phenology is crucial for adaptation against the increasing trend in temperature in the upcoming decades. The goal of this research was to quantify the impact of historic climate warming and management on sunflower phenology (stages and phases). In this project, spring and fall sunflower phenology and daily weather data were obtained for 20 locations in Punjab, Pakistan. We investigated the impact of thermal trend on the phenological stages and phase duration for spring and fall sunflower from 1980 to 2016. The results showed that the mean temperature increased by 0.9 and 0.8 degrees C decade(-1) for spring and fall, respectively. The observed phenological stages such as sowing, emergence, anthesis, and maturity dates were earlier for spring by an average of 6.6, 6.3, 3.8, and 2.2 days decade(-1) and delayed for fall by an average of 5.7, 5.4, 3.1, and 1.8 days decade(-1). The observed sowing to anthesis, anthesis to maturity, and sowing to maturity phases were reduced by an average of 2.8, 1.6 and 4.4 days decade(-1) for spring and 2.5, 1.2, and 3.8 days decade(-1) for fall. The changes in phenology of sunflower for spring and fall were highly correlated with the enhancement in warming trend during 1980-2016. The CSM-CROPGRO-Sunflower model using standard hybrids for all sites and years showed that the simulated phenology had accelerated due to the change in climate and the simulated phenological dates were earlier than the observed dates. These results indicate that earlier sowing dates for spring, delayed sowing dates for fall, and shifts of varieties that require elevated total growing degree days for the duration of 1980 to 2016 have somewhat mitigated the adverse impact of climate warming on spring- and fall-grown sunflower phenology for ensuring sustainable productivity and ensuring food security.