Study of soybean competitive ability under interference conditions with different densities of Asian spider flower (Cleome viscosa L.): invasive weed in Golestan province.
Field studies were conducted in Iran, in 2015-16, to investigate the effect of different densities of Asian spider flower (Cleome viscosa) on the growth characteristics of soyabean and determine the soyabean yield loss due to competition with different densities of this weed species. The treatments comprised soyabean (cultivar D P X) under interference condition with different densities of Asian spider flower (0, 3, 5, 10, 15, 20, 30, 45 plants/m2). Sampling was done at 25 days after planting in 8 stages. In each sampling, the leaf area and dry weight of soyabean and Asian spider flower were measured. Vertical distribution of leaf area in canopy profiles of soyabean and Asian spider flower was also studied. For this purpose, plants were divided into segments in 20 cm intervals and the leaf area of each layer was measured separately. A 2-parameter rectangular hyperbolic function was used for estimating grain and biological crop yield loss. Finally the accuracy of the model was confirmed based on RMSE, r and the dispersion of the observed and predicted grain and biological yield loss of soyabean around the one to one line. The results showed that Asian spider flower was a strong competitor to soyabean. According to the results, it seemed that some characteristics of Asian spider flower including representing greater height at the end of the growing season, requiring a shorter time to reach maximum leaf area index and arranging a greater part of plant leaf area at higher canopy layers compared to soyabean, were the most important factors to increase the competitive ability of this weed.