This study was conducted to evaluate the effects of planting  arrangement and phosphate biofertilizer on soybean yield and  yield components under different weed interference periods at the  Agricultural Research Farm of Razi University, Kermanshah,  west Iran. The experiment was a factorial with three factors  arranged in a randomized complete block design with four  replications. The first factor wa s planting arrangement (50 and 5  cm (P1) or 25 and 10 cm (P2) for inter-row and inter-plant  spacings, respectively), the second factor was phosphate  biofertilizer (no-inoculation (I0 ) and inoculation (I1)) and the  third factor was weed treatment (full season weed-free condition  (W0), weedy condition until soybean 4-trifoliate stage (W1), weedy condition until soybean flowering stage (W2) and full  season weedy condition (W3)). Resu lts revealed that the highest  soybean yield occurred when weeds were controlled throughout  the growing season and soybean was planted at the inter-row and  inter-plant spacings of 25 and 10 cm, respectively (P2) whether  phosphate biofertilizer was used or not. For both planting  arrangements, full season weedy condition at the lack of the  biofertilizer led to the lowest soybean yield produced. Weed  biomass was not significantly affected by use of biofertilizer. The  highest weed biomass was established in plots without weed  control throughout the whole growing season and soybean was  planted in a wider row spacing and a less uniform spatial  arrangement (P1). Moreover, For W2 and W3 treatments, soybean  planted in a narrower row spacing and a more uniform spatial  arrangement (P2) produced a notable lower weed biomass, so that,  this planting arrangement reduced weed biomass by 31.8 and  31.7 % in W2 and W3, respectively as compared to the P1  planting arrangement. It can be co ncluded that soybean planting in  a more uniform spatial arrangement via a narrower row spacing  can significantly improve soybean yield and suppress weeds.  Phosphate biofertilizer had no sign ificant effect on soybean yield  when soybean was planted as the P2 and weeds were controlled  throughout the growing season