In order to evaluate different proportions of intercropping potato ( Solanum tuberosum L.) and pinto bean ( Phaseolus vulgaris L.) with their sole cropping, two experiments were carried out in Agricultural Research Station of University of Tabriz in 2005 and 2006, using randomized complete block design with three replications of eight treatments of replacement intercropping with proportions 2:1 and 3:1 of potato with pinto bean, (the densities of potato 4.7 and 5.3 plants per m 2 and those of pinto bean 45 and 55 plants per m 2) along with two sole cropping treatments of potato (4.7 and 5.3 plants per m 2) and two sole cropping treatments of pinto bean (with 45 and 55 plants per m 2). In all intercropping plots, tuber yield per m 2 and per plant, number of leaves and branches and size of tuber per plant increased significantly as compared with their sole croppings. For pinto bean also, grain yield per m 2 and per plant, number of pods per plant and number of leaves and branches per plant increased significantly as compared with their sole croppings. Highest amounts of LER in two years (1.25 and 1.27) were related to intercropping proportion of 2:1 (66% potato with density of 5.3 plants per m 2+34% pinto bean with the density of 55 plants per m 2). We can infer that these two crops have used more environmental resources in intercropping than sole croppings due to increase in Resources Use Efficiency (RUE).
