Introduction soybean (Glycine max L.) plays an important role in three major markets of grains, oil and meal. damage of weeds in soybean generally 13 to 60 and sometimes more than %80 have been reported Farming methods through proper management, sowing date and by use of optimum density could be a strategy for the development of ecological competitiveness of crops and inhibit weed growth are the comparison the growth indices to design interference models of weed and crop and estimate crop yield

more »

... loss in competition with weed is essential and allow to plant breeding researcher to choice the more competitive varieties of crop in competition with weed. Materials and Methods With the aim of influencing sowing date and plant density on the growth indices and evaluation the competitive ability of soybean cultivar Williams with weeds, an experiment was conducted in 2013, at Agricultural Research Station, Ferdowsi University of Mashhad, as split-split based on a randomized complete block design with three replications. Main plot included three sowing dates levels (17 April, 12 May, 6 June) and sub - plots included four crop density (30, 40, 50 and 60 plant . m-2) and sub - sub plots included weed management of two level (weed infested and weedy control). First sampling was started at 35 days after planting and was every 14 days until the end of growth period. Leaf area index, dry matter, crop growth rate and the growth rate were calculated Results and Discussion The results showed that 11 species weed belonging to 9 families observed and identified. In the early stages of growth, leaf area index and dry matter increased slowly, but in the seven to eight leaf stage of plant growth (Log phase), leaf area index and dry matter increased rapidly, and a little upon entry to the plant Physiological maturity period (Early seedling) peeks, and again began to decline at the end of seedling. The sowing date 12 May in contrast to early sowing date (17 April) and delayed planting date (6 June) produced greater leaf area index, dry m [...]