Effect of Sowing Date on Grain Yield and Related Agronomic Characteristics and Determinaation of the Optimum Sowing Date Window for New Bread Wheat Cultivars in Warm and Dry Regions of Fars Province

This study was conducted to investigate the effect of sowing date on grain yield and agronomic charcteristics and to determine the optimum sowing date for new bread wheat cultivars in the warm and dry agro-climatic conditions of Fars provienc. The experiment was carried out as split plot arrangements in randomized complete block with three replications at Darab agricultural research station in 2018- 19 and 2019-20 cropping seasons. The main plots consisted of five sowing dates; 27 October, 11 November, 26 November, 11 December and 26 December, and the sub-plots included five bread wheat cultivars; Mehergan, Barat, Khalil, Sarang and Setareh. The highest and lowest mean grain yield obtained from 11 November (6930 kg ha-1) and 26 December (5770 kg ha-1), respectively. The relatively late cultivar; Khalil had higher grain yield than other cultivars in early sowing dates. The early cultivars; Setareh and Mehregan had higher grain yield in latest planting date (26 December) compared to the earliest planting date (27 October). Sarang cultivar with a mean grain yield of 6650 kg ha-1 had the lowest yield variation in the studied sowing dates. The recommended sowing date window and the optimum sowing date were different for each cultivar and varied from November 16 to December 16. These results indicate that the selection of early cultivars is very effective factor in integrated crop management for reducing grain yield losses due to delay in sowing date in warm and dry regions of Fars province and similar agro-climatic conditions in Iran.