To study the effect of different densities on the trend of growth, yield and its components of three varieties of soybean under the climatic conditions of Kermanshah, an experiment was carried out in research fields at Mahidasht, Kermanshah in 2003. The factorial experiment had four replications arranged in random complete blocks design. Three varieties, i.e.  Williams, Zan and Clark were placed in the blocks at three density   levels with plants spaced at 3, 5 and 7 cm rows in the blocks. The highest dry weight was obtained from variety Clark. With increasing plant density, dry weight was observed to decrease while the leaf area index increased.  At higher plant density the crop growth rate (CGR) tended to increase but was at its maximum at density D2 (medium). Comparison of changes in the relative growth rate (RGR) showed that variety Williams at density D3 (lowest) had the highest RGR of all varieties and densities. In this study density increase caused an increase in plant height, the interface of the first sub-branch from soil surface, length of inter node, number of nodes in main branch, number of grain in pod per plant, grain yield per unit area, and biological yield performance. However, increased density caused a reduction in the number of branches, node length, pods, grain yield per plant and sub branch and dry weight of grain. The percentage protein and oil content, harvest index, 100grain weight on the main and sub branch and plant, and the number of grain in  pod of main and sub branch were not affected by plant density. The highest number of nodes, pods per node and 100 grain weight was obtained on cv. Clark while the highest number of grain per pod belonged to cv. Williams.

Key words
Planting density, variety, yield, yield components, growth analysis

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