SEED AND OIL PRODUCTIVITY OF SUNFLOWER (Helianthus annuus L.) AS AFFECTED BY THE TIMING OF WEED REMOVAL

Sunflower, one of the most important oil crops, is generally considered to be very competitive against weeds. However, this is not valid for all hybrids, weeds and conditions, since in many cases there have been reported yield losses up to 70%. A field study was conducted in western Greece to evaluate growth. grain and oil productivity of sunflower under different weed management treatments (weed free, weed presence for 2, 4 and 8 weeks after sowing). Grain yield of the several treatments resulted to losses up to 64% compared with the weed free plots. Oil concentration was not affected by the presence of weeds, however oil yield was also significantly reduced in the plots with a late weed removal, probably due to the seed yield reduction. The findings of the present study reveal the significant reduction of seed and oil productivity in sunflower due to weed competition and highlight the need of an early weed management.