Evaluating Competition and Yield of Two Soybean Cultivars Under Pure Stand and Intercropping Systems

In order to investigate the competition effect and yield of two soybean cultivars in pure stand and intercropping systems, a factorial experiment based on randomized complete block design with three replications was conducted in field, 22 kilometers from Gorgon-Sari in 2002. Factors were: soybean cultivars Pershing and Williams with three densities (40, 50 and 60 plants m-2) and six levels of planting patterns of Pershing-Williams(0:100, 20:80, 40:60, 60:40, 80:20, 100:0). The competition models of reverse productivity for Willims and Pershing in pure stand was Cayera equation and for intercropping were Shenozoki and Cayera equations. The reverse productivity of single plant in pure stand in both cultivars had a linear relationship with plant density. The results showed that productivity of Williams single plant was equal to 1.2385 of Pershing and the single plant productivity of Pershing was equal to 0.9212 of Willims. The intracultivar competition in Willims was more than intercultivar competition, while in Pershing it was vice versa. The differences between inverse productivity of single plant of Williams in pure cultivation and intercropping was very low. But in Pershing this difference was relatively high, which shows that Willims cultivar is more competitive than Pershing. The highest yield was obtained at the ratio of 40:60 with 50 plantsm-2 and land equivalent ratio of 1.21.