Towards shifting planting date as an adaptation practice for rainfedwheat response to climate change

Abstract

tMaintaining rainfed crop production particularly in water-limited environments is of great impor-tance for agricultural water management under climate change (CC). In such conditions, there is a realdemand for finding some practical adaptation scenarios to sustain optimal crop production. This studyaimed to investigate the impacts of CC on rainfed wheat yield, transpiration to total evapotranspira-tion ratio (T/ET) and maximum leaf area index (LAIm) in some semi-arid areas in Iran over 2071–2100under the current and shifted planting date scenarios. Consequently, the outputs of five climate mod-els under RCP-4.5 and RCP-8.5 emission scenarios downscaled by MarkSimGCM were used to run theCSM-CERES-Wheat v4.6 model. Results revealed that crop yield, T/ET and LAIm will decrease chiefly dueto October–November–December (OND) and January–February–March (JFM) precipitation deficit undercurrent sowing date at the most studied sites. Unlike early planting, postponing sowing date from thecurrent to the best date as an adaptive alternative will increase the received precipitation during twoearly growth phases i.e. germination to terminal spikelet initiation (G-TS) and terminal spikelet to end ofleaf growth and beginning of ear growth (TS-ELG). However, a considerable change in the precipitation ofentire growing season and grain filling (GF) stage due to delay in sowing date was not projected. EnhancedG-TS rainfall will ensure crop emergence and establishment. Moreover, precipitation increase at TS-ELGphase in which the highest decrease of precipitation was predicted, would enhance LAIm and T/ET. Thiscan be attributed to the fact that the vapor flux in the soil–plant–atmosphere system may shift in favor oftranspiration loss through delaying planting date. Therefore, by better matching crop development withchanged rainfall distribution, postponing sowing date can partially compensate the deleterious impactsof CC-induced drought on rainfed wheat yield in the west and northwest Iran during 2071–2100.