Modeling the response of sesame (Sesamum indicum L.) growth and development to climate change under deficit irrigation in a semi-arid region

Abstract

The future climate outlook was based on a combination of CCMs based on three Representative Concentration Pathway (RCP) scenarios including RCP 2.6, RCP 4.5 and RCP 8.5 for the future period of 2021–2051. The results showed an increase of the average Tmax in June, July and August (averaged by 1.8°C compared to the observed period) and a decrease in rainfall in May to September (averaged by 30.76 mm compared to the observed period under all three scenarios. Estimation of phenological stages of sesame under different scenarios showed that with increasing Tmax in April and May, the beginning of flowering, grain filling and physiological maturity was accelerated, also with increasing temperature from June to August the duration of the phenological stages was decreased. The effect of deficit irrigation (DI, supplying of 50% plant water requirement) on sesame phenological stages was not significantly different from full irrigation (FI). Simulation of canopy cover evolution (CC) and dry matter accumulation using the AquaCrop model revealed that the length of the late-season and the mid-season stages, have the greatest liability to be changed under the future climate change. Under the studied scenarios, the beginning of sesame growing season will accelerate from 9 to 11 days, which makes possible delayed sowing of sesame. The average of biomass (B) produced under three scenarios in DI and FI conditions were 17920 and 17241 kg ha-1, and the average of grain yield (GY) was 2905 and 3429 kg ha-1, respectively, which shows an increase by 31.5% and 28.7% of B, 18.4% and 39.5% of GY, compared to the observations (year 2016). The results revealed that under the future climate (except for RCP8 scenario), DI strategy can be used without reducing the GY of sesame due to the very little reduction (1.2%) in GY under DI compared to FI.