Investigation of Delay Cropping on assimilate remobilization, Yield Components and Yield of Two Safflower Cultivars under Cutting off Irrigation

The shortage of oilseeds and the high volume of oil imports in Iran and the limitation of water resources for the many oilseeds production, showed the necessity of identifying species and varieties adapted to these stressful conditions and determining the most sensitive stages. Nowadays, safflower, due to drought resistance, is considered as a plant crop in the Iranian crop rotation. Therefore, whith respect to importance of water stress and selection of appropriate planting date in crop production, this research was conducted to investigate the effect of delay cropping and irrigation regime on assimilate remobilization, yield components and yield safflower.

In order to investigate the effect of delay cropping and irrigation regime on assimilate remobilization rate, yield components and yield of safflower , a field experiment was conducted as split factorial in a completely randomized block design with three replicates at Agriculture College and Natural Resources of Darab, Shiraz University, during 2018-2019 growing season. Experimental factors consisted of irrigation regimes in three levels included normal irrigation, Cutting of irrigation at flowering and Cutting of irrigation at seed filling, three planting dates (6 December, 26 December and 15 January) and two safflower cultivars (Goldasht and local Isfahan). In this research, dry matter remobilization, remobilization contribution and remobilization efficiency, yield components and yield of safflower were determined.

Results showed that the measured traits were affected by irrigation regime, planting date and cultivar, significantly. Cutting of irrigation at flowering reduced number of capitule per plant, number of seeds per capitule, 1000-seed weight and grain yield of safflower cultivars by 21.86%, 23.87%, 28.37% and 33.74%, respectively compared to normal irrigation. The amount of dry matter remobilization, remobilization contribution and remobilization efficiency in cutting of irrigation at flowering increased 30.44%, 37.81% and 25.37%, respectively compared to normal irrigation. Also, delayed third planting date (15 January) reduced dry matter remobilization (44.17%), remobilization contribution (22.72%), remobilization efficiency (17.88%), number of capitule per plant (%). 14.57, number of seeds per capitule (20.65%) and grain yield (13.31%).

Cutting of irrigation at flowering and seed filling treatments decreased 52.32% and 34.54% of grain yield in Isfahan local cultivar at second planting date (26 December) compared to the normal irrigation treatment, respectively,. However, seed yield in this treatment did not differ significantly with the treatment of cutting of irrigation at seed filling in planting date on 6 December in Isfahan and Goldasht cultivars which seems to be due to increased assimilate remobilization and remobilization efficiency in cutting of irrigation at seed filling compared to normal irrigation. Therefore, selection of optimum planting date (26 December) compared to early planting date (6 December) and early mature Goldasht cultivar by 12.91% higher yield can be an appropriate strategy to improve and increase safflower seed yield under late season water stress in semi-arid regions.