Effect of Planting Date and Weed Control Methods on Yield and Agronomic Traits of Sunflower (Helianthus annuus L.) in Khoy Region

Effects of planting dates and weed control methods on yield and agronomic traits of sunflower was investigated. A factorial experiment based on a complete randomized blocks design with four replications was conducted in 2009. Treatments consisted of three planting date (April 4th, May5th and Juns5th) and five weed control methods, Trifluralin (2 Lit/ha) Fokus (1.5 Lit/ha), Trifluralin㖦s (3Lit/ha), Trifluralin, Hand weeding and without control. Results indicated that planting dates and weed control methods significantly affected head diameter, 100 grain weight, seed number per head and grain yield. Harvest index and oil percent was affected only by planting dates. The highest grain yield (630.1 g/m2), was produced in the second planting date (May 5) by using Trifluralinᚉ. Delaying sowing date (after May 5) significantly decreased grain yield. The most important weeds in the experimental site were common lambsquarter (Chenopodium album), field bind weed (Convolvulus arvensis), bastard cabbage (Rapistrum rugosum), flower-of-an-hour (Hibiscus trionum), cockspur grass (Echinochloa colorum) and green bristle grass (Setaria verticillata). It was observed that the dry matter weight sharply varied in all weed species in different planting dates, that is, in the 4th April the dry matter production of common lambsquarter and bastard cabbage, in June 5th planting date were maximum. Dry matter of broad leaf and narrow leaf weeds in the date of May 5th was lower than the other two planting dates. The interaction of planting date ×control methods on head diameter, seed number per head, grain yield and weeds dry matter was significant.