عنوان مقاله [English]
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 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 matter and growth rate. Low temperature in the early stage of growth early planting and the reduced length of the growing season due to the high temperature in delayed planting results in reduced leaf area index and dry matter. The more density, the later sowing date results in the more dry matter and leaf area index. Maybe, sowing date together with more density was compensated yield loss. The presence of weeds in soybean density from 30 to 60 plants per square meter, the leaf area index and dry matter increased. Most of crop growth rate (22.24) was observed in sowing date, 12 May and with 50 plants per square meter and without weed. The maximum growth rate (0.127) was observed on sowing date 6 June and 40 plants per square meter and in condition of weed control. difference between the dry matter, leaf area index, crop growth rate and the growth rate in condition of weed interference (all season) were significant Results indicated that the maximum economic yield is related to sowing date, 12 May and 40 plants per square meter. Also, in this situation improved growth indices and increased competitive ability against weed were observed.
Conclusions The results of this study showed that dry matter, leaf area meter, crop growth rate and the growth rate in the presence of weed were declined. Early and late planting reduced dry matter, leaf area index and the rate of growth of soybeans. It̓̓s concluded that such t the low temperature in early growth period in early planting and reduced length of growing season delayed planting due to the high temperature reduced dry matter, leaf area index. The low density (density 30 and 60 plants per square meter) impacted growth indicators. There for, the density should be selected based on plant, ecological needs during environmental conditions and the growing season. In conclusion the sowing date 12 May and density 40 plants per square meter are the best condition that improve growth indices and increase the competitiveness of soybean against the weed, and these are as ecological solution for reduced pesticide usage and reduced the effects of environmental pollution and men's health.