Modeling chickpea yield of rain-fed in dormant seeding using general circulation models in west and north western of Iran

According to global warming and climate change, investigating and assessing the efficiency of adaptation strategies are necessary for achieving agricultural sustainable development under future climate conditions. Change in sowing date and dormant seeding for crops can be considered as a suitable strategy to adapt with changing climate conditions. Under dormant seeding management (DSM), the seeds remain ungerminated in the soil, and germinate and emerge with the onset of warming thanks to climate change exploiting late-winter rainfalls, and consequently decreasing frost risk stress at seedling stage and increasing water use efficiency. The main objective of the current study was to investigate the effect of sowing dates especially dormant seeding on rainfed chickpea seed yield in Kermanshah (West) and Tabriz (Northwest) climatic conditions.

In the current study, three general circulation models (MPI-ESM-LR, MPI-ESM-MR and NorESM1) were used under two emission scenarios (RCP4.5 and RCP8.5) for the future of 2039–2069 in Kermanshah and Tabriz regions. GCM outputs were downscale by AgMIP methodology. The SSM-Chickpea model was employed to simulate the growth and development of chickpea (Soltani and Sinclair, 2011). Five sowing dates including 21 December (DSM), 6 March, 21 March, 4 April and 21 April were considered as an adaptation strategy to possible impacts of climate change. Study traits included leaf area index, number of days to maturity, mean temperature over the growing season, cumulative rainfall, evapotranspiration, biological yield, and grain yield.

The results of model validation showed that the model was able to predict the grain yield reasonably well (R2=0.92 and RMSE=14%). Overall, averaged grain yield at all sowing dates in Tabriz was 131% more than Kermanshah in the baseline. High grain yield in Tabriz compared with Kermanshah can be attributed to more leaf area index and length of growing season. Averaged grain yield in dormant seeding was 13.51, 22.30, 31.94 and 46.86% higher compared to 6 March, 21 March, 4 April and 21 April, respectively in both locations at the baseline. On average (GCMs, emission scenarios and locations), dormant seeding had the highest grain yield (24.93%) than other sowing dates in future climate change conditions compared to baseline. The reasons of superiority of dormant seeding of chickpea compared to other sowing dates was due to coinciding of crop growth period with rainfall (Hajjarpoor et al., 2016), reduction in negative effects of high temperatures on grain yield especially during grain filling (Hajarpour et al., 2013), increasing transpiration efficiency due to lower temperatures over the growing season (Soltani et al., 2006) and escaping terminal drought stress at end of growing season. Averaged grain yield (locations, sowing dates and GCMs) under RCP4.5 and RCP8.5 scenarios increased by 8.97 and 14.12% compared to baseline. Increasing grain yield was due to the positive effects of boosting the carbon dioxide concentration on the photosynthesis rate of chickpea as a C3 plant under changing climate (Meghdadi et al., 2014).