Early sowing date as a strategy for improvement of maize yield and maize physiological and phonological characteristics in climate change conditions at Kermanshah Province

Climate change can directly affect on worldwide food security because climate change processes (such as increasing of CO2 concentration and temperature and variability of precipitation) have directly affect on crops. Corn such as C4 plants that are sensitive to climate changes. Therefore to reduce the sensitivity of the maize in the face of climate change, we need to apply adaptation strategies. One of the effective strategies is the changes in sowing dates. Many of studies have shown that changes in sowing dates (particularly the use of early planting dates) can reduce the negative effects of climate change.
This research was conducted in three locations of Kermanshah Province. Accordingly, the future climate in the study areas was generated using long-term (1980-2009) climate data of the baseline (included minimum and maximum temperatures, rainfall and global radiation) and AgMIP technique under two climate scenarios (RCP4.5 and RCP8.5) for the future period of 2040 -2069. Long-term simulation experiments consisted of five sowing dates (5st April, 20st April, 5st May, 20st May, 5st June), three locations (Kermanshah, Kangavar and Eslamabad), two future climate scenarios (RCP4.5 and RCP8.5) in 30 years. In total, around 1350 simulation experiments were carried out. In this study, APSIM crop model was used for simulation of maize growth and yield. In this study, all of the simulations were conducted in potential conditions and water- and nitrogen-limited production situations were not considered in the current study. APSIM model has previously been calibrated and evaluated for SC704 cultivar (this cultivar is the most common cultivated cultivar in the Kermanshah Province). In current research, all the output data was analyzed, graphed and mapped using the R software package (R Core Team, 2016) and OriginPro9.1 (Seifert, 2014).
Average grain yield of Kermanshah Province was 11354 kg ha-1 in the baseline. Results showed that in 2050, on average grain yield was reduced 60.82 and 80.73 % (under RCP4.5 and RCP8.5, respectively) compared to baseline. In different locations, the highest and lowest grain yield in the baseline were recorded in the Kangavar with 13426 kg ha-1 and Kermanshah with 7952.4 kg ha-1. When averaged across locations, the highest grain yield in the climate change conditions was obtained in an early sowing date (5st April) with 7071.2 and 4743 kg ha-1 (under RCP4.5 and RCP8.5, respectively). In future on average (two scenarios) duration of growth period, vegetative and reproductive growth periods (4.7, 4 and 1.7 %, respectively) were decreased compared to the baseline. Also, in future, the number of grains and grain weight were reduced in Kermanshah Province so that under RCP4.5 were 56.5 and 31.8 %, respectively and under RCP8.5 were 78.5 and 59.3 %, respectively. However, these reductions in duration of growth period, vegetative and reproductive growth periods, the number of grains and grain weight were less in 5st April early sowing date than other sowing dates (especially late sowing dates).
Generally, results of the current study indicated that climate change had negative effects on maize yield and maize physiological and phonological characteristics in Kermanshah Province. However, early sowing dates might reduce these negative effects. So that in most cases, 5st April can reduce negative effects on maize yield and maize physiological and phonological characteristics in the future period.