Evaluation of Corn-Soybean Intercropping Advantages Using Agronomic and Weed Control Efficiency Indices

In this study effect of additive intercropping of different soybean densities on economic and biological yield of corn and index of weed control efficiency was evaluated at the climate condition of Hamedan during growing season of 2011. Complete randomized block design (RCBD) with three replications and five treatments included T1 and T2; Pure stand of corn with and without weeding، respectively and T3، T4 and T5; additive intercropping of 15، 30 and 45 percent of pure stand of soybean (40 plants per m-2) with corn، respectively. Results indicated that experimental treatments had significant effects (p<0. 01) on grain and biological yields of corn. But، the effect of treatment on harvest index was not significant. The highest grain (803 g m-2) and biological (1793 g m-2) yield were achieved at T1 (Pure stand of corn with weeding) treatment. However، there is no significant difference for these traits between T1 and T5 (additive intercropping 45 percent of soybean with corn) treatments. Using soybean as a companion crop had significant effect on weed control. As، minimum values of weed biomass and weed density; in averaging 53 g m-2 with 17 plant m-2 and 52 g m-2 with 8 plant m-2 were observed at T4 and T5 treatments، respectively. Treatment of T5 can be introduce as a best treatment، because it can suppress weeds in the corn field and had the lowest value of competition index (0. 04)، the highest values of land equivalent ratio (1. 27)، total relative value (1. 33) and weed control efficiency (83. 20%) and produced the highest value of grain yield (758 g m-2).