Effect of different cover crops and nitrogen split on control of biomass and density of annual and perennial weeds of forage corn

In order to evaluate the use of cover crops to control weeds in forage corn an experiment with three factor factorial in a randomized complete block design with three replications was done in 2012 at the Agricultural Research Station (Samian) Ardabil. The first factor of treatments consists of rye, hairy vetch, clover as a cover crop and no cover crop with maize cultivation practices and without weed control. The second factor consists of nitrogen split of 225 kg urea per hectare with 2 levels, the first level (1/2 at sowing + 1/2 in the 8 to 10 leaf stage of corn), second level (1/3 at planting + 1/3 in the 8 to 10 leaf +1/3 a week before tasseling of corn) to the desired split in two and three corn growth stages were used. The third factor consisted of two levels of weed sampling frequency of 60 days and 90 days after planting corn. Combined analysis of variance showed a rye cover crop, hairy vetch and clover annual weed biomass compared to the control treatment (no cover crop and no weeding), which is equivalent to 190.33 grams per square meter was respectively 90, 84 and 66 percent of annual weed density compared to control (without plant cover and without weeding), respectively 70, 54 and 32% decreased. Also mentioned coating plants, decreased perennial grass biomass than the control treatment, respectively 62, 50 and 22% and density of perennial weeds compared to control decreased 80, 76 and 59% respectively. Cover crops and nitrogen split interactions have significant effects on plant height, diameter and length of corn ear, so that the maximum height, diameter and length of corn ear of weeds and weeding treatments were fertilizer levels split second. The highest fresh forage yield of corn (51.3073 ton per hectare) of weeding treatments were full of weeds. After weeding treatments, forage yield compared to hairy vetch cover crop treatment, with the most significant difference. Overall, taking into account the interests of more effective control of weeds and forage production, treatment of hairy vetch cover crop and the second split of nitrogen fertilizer level was appropriate.