Study on the effect of planting date and plant density on grain yield, yield components, forage quality, oil amount of different safflower cultivars in the Gonbad-e Kavus region

The majority of the country's oil consumption comes from foreign sources. Therefore, the development of oilseed crops is critical. Safflower has a special status among oilseed grains adapted to the country's conditions, and it is ecologically compatible with many agricultural lands in the country. Research has shown that planting date and plant density significantly affect the yield and yield components of crops. Over the past few years and in different Iran regions, several cultivars have been isolated from safflower, which may vary in response to planting date and plant density. Therefore, this study was conducted to study and determine the most suitable planting date and plant density for the advanced safflower cultivars and their effect on grain yield, forage, oil, and yield components in the Gonbad-e Kavus area.

This study was conducted with two separate factorial experiments (the first experiment on 30th of November and the second on 20th of December) in a randomized complete block design with four replications at the Agricultural and Natural Resources Research Station of Gonbad-e-Kavus in two seasons of 2013-14 and 2014-15. In each experiment, two sowing densities of 20 and 40 plants per square meter (10 and 20 cm plant distance on the row) and four advanced safflower cultivars included: Golmehr, Soffeh, Padideh, and Goldasht, were combined as factorial and formed eight treatments. Seeds of the mentioned cultivars were prepared from the Golestan Agricultural and Natural Resources Research and Education Center. The row spacing was fixed at 25 cm for all treatments. SAS software was used to analyze the data, and the mean comparison of the data with SPSS software was performed as the least significant difference (LSD) test.

The results showed that the effects of planting date on the branch number plant-1, grain yield, oil percentage, forage ash, and the dry matter intake were significant. The influences of sowing density on branch number plant-1, 1000-seed weight, and oil percentage were significant. There were significant differences among the cultivars according to the branch number plant-1, and safflower seed oil percentage. The mean comparison of data showed that the highest branch number plant-1, grain yield, forage ash, and the dry matter intake were observed in the first planting date, and the delayed sowing decreased these traits significantly, while oil percentage showed a significant increase. Increasing the sowing density induced the branch number plant-1, 1000-seed weight, and oil percentage significantly. The forage yield showed a positive significant with grain yield and crude protein.

In terms of safflower planting date, it was observed that the first planting, due to suitable climatic conditions and longer growing period, had better results in the branch number plant-1, boll number plant-1, oil content, forage ash, and dry matter intake traits. With increasing plant density, branch number plant-1, 100-seed weight, and oil percentage decreased significantly, so due to the importance of oil content, 20 plants per square meter is recommended. According to this study's results, the Soffeh cultivar could be used for the earlier sowings, but there was no significant difference in grain yield among the cultivars with delayed sowing. So, four studied cultivars Golmehr, Soffeh, Padideh, and Goldasht, could be cultivated under the delayed planting date conditions, and it is suggested that selection of safflower cultivar should be made according to the purposes of safflower planting (forage, oil, or seed breeding).