response- surface analysis for evaluation of competition in different densities of sesame (sesamum indicum) and bean (phaseolus vulgaris) intercropping

response surface models predict crop yield based on crop density and this is an important tool for evaluation competition at different density and hence selection of optimum density based on yield. in order to study intra and inter specific competition in intercropping bean (phaseolus vulgaris) and sesame (sesamum indicum), an experiment was conducted at the agricultural research station, ferdowsi university of mashhad during the growing season of 2010. for this purpose a complete randomized block design with 3 replications and 16 treatments based on different densities of sesame and bean intercropping was used. the model predicted the maximum yield of an isolated plant of bean and sesame approximately 33 and 17g per plant respectively. the area associated with the maximum yield per plant in bean and sesame were 0.6 and 0.1 m2, respectively. bean was the dominant competitor with respect to both grain and biomass, and competition coefficient was 0.35 and 0.3 for bean grain yield and bean biomass respectively. intra-specific competition was more important than inter-specific competition for bean. competition coefficient was 2.6 and 2.9 for sesame grain yield and biomass respectively. intra-specific competition was much less important than interspecific competition in sesame. the highest grain yield in bean (300 g m-2) was obtained of sole crop with density of 20 plants, and the highest sesame grain yield (195 g m-2) was obtained of sole crop with density of 40 plants, the highest land equivalent ratio (1.14) was obtained in intercropping of 20 plants of bean and 10 plants of sesame.