The effect of cover crops on weed control and improving seed yield and growth characteristics of hybrid sunflower (Helianthus annuus)

Recently, the planting of narrow lead cover crops has had a noteworthy effect in reducing the use of herbicides. This experiment was carried out during 2011-2012 at the Natural Resources research station in Samian (Ardabil Province) as a factorial study in a randomized complete block design with 3 replications. The first factor included three types of cover crops, rye (Secale cereal), barley (Hordeum vulgare) and wheat (Triticum aestivum) with two controls: (1) without cover crops, with complete weeding and (2) without cover crops and without weeding. The second factor involved management at two levels (live mulch and non-living mulch) and the third factor was with two levels of cover crop planting date (synchronic with planting sunflower and 45 days after planting sunflower). Results showed that the effect of cover crops was significant on sunflower seed yield, protein percent and yield, shoot dry weight, head dry weight and height. The highest seed yield was obtained at control 1 (4053.3 kg ha-1) and in wheat and rye cover crop traits were 3916.7 and 3798.3 kg ha-1, respectively. The highest protein (42.51%) and protein yield percentages (1.69 t ha-1) were observed in control 1 (without cover crops, with complete weeding). Also, the maximum height (173.73 cm) was related to synchronic planting of cover crops with sunflower. The highest single seed weight mean was observed in live mulch management in synchronic planting (0.087 g m-2) and in dead mulch management at 45 days after planting (0.089 g m-2). The interaction of cover crops and planting date had significant effects on weed density and dry weight so that the minimum density and total dry weight of weeds were observed in the cover crops of rye, wheat, barley respectively and at the same planting date. The maximum density and dry weight of weeds were observed in control 2 (without cover crop, without weeding).