Effect of cover crops on weed criteria and quantitative and qualitative yield of caster bean (Ricinus communis L.)

In order to evaluate the density and dry weight of weeds and seed and oil yield of castor bean Ricinus communis L.) as a medicinal plant affected by cover crops، an experiment was conducted at the Agricultural Research Station، Faculty of Agriculture، Ferdowsi University of Mashhad، during growing season of 2008-2009. Treatments were four cover crops included white clover، fenugreek، hairy vetch and rough and control (without cover crop). Criteria such as relative density، density and dry weight of weeds at five sampling stages and seed and oil yield of castor bean. The results showed that the lowest relative densities were observed in knot grass (0-1. 75%)، purslane and pigweed (5. 88-23. 80%)، purslane (1. 43-23. 80%)، redroot amaranth (5. 88-27. 77%) and field bind weed (5. 55-26. 66%) at the first، second، third، fourth and fifth sampling stages، respectively. The effect of cover crops was significant (p≤0. 05) on density and dry weight of weeds at the different sampling stages and seed and oil yield of castor bean. The minimum and maximum total densities of weeds were achieved in hairy vetch and control with 378. 67 and 1021. 39 species. m-2، respectively. The highest seed and oil yield of castor bean were recorded in hairy vetch with 475. 94 and 182. 75 kg. ha-1، respectively. Generally، it concluded that cover crops are ecological weed management and improvement in quantitative and qualitative yield of medicinal plants such as castor bean.