Effect of Planting Date and Plant Density on Yield, Harvest Index and Calendic Acid Content of Two Varieties of Marigold (Calendula officinalis L.) in Arak

In order to determine the effect of planting date and plant density on Marigold (Calendula officinalis L.) varieties، a split-factorial experiment with three replications was carried out at Agricultural Station of Arak in 2007 growing season. The experimental factors included two planting dates (22 April and 2 May)، four planting densities (26، 32، 41 and 57 plant per square meter) and two varieties (Sparse and Compact petal). Results indicated that the treatments had significant effects on dry flower yield، petal dry weight، seed yield، biological yield، seed harvest index، oil percentages and Calendic acid percentages. Early planting، high density and compact petal variety enhanced the mentioned traits except harvest index. The highest harvest index was achieved in 26 plants per square meter by compact petal variety and second planting date. The late planting date decreased the Marigold yield components. Seed planting in 2 May compared with 22 April decreased 18. 22 % of flower dry weight. The compact petal variety had higher yield compared to sparse petal variety. Compact petal variety improved the biological yield and seed yield 9% and 10% respectively، in comparison with sparse petal variety. Based on three way interaction of treatments results، the highest percentages of oil (17%) and Calendic acid (51%) achieved by 2 April planting date in 57 plants per square meter density with compact petal variety.