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Soybean is important grain and oil crop in China. In recent years, seeds of Dature stramonium were often found in imported soybean, which always resulted in trade friction. Besides, D. stramonium had been considered as common companion weed in soybean fields. In order to understand the damage degree, pattern and principle of D. stramonium, provide scientific evidence to preliminary pest risk assessment of the invasion of D. stramonium to soybean fields, some laboratory and field tests were carried out, respectively. In laboratory tests, we used the techniques of laboratory bioassay to study the effects of D. stramonium extract on the germination rate, germination index, root length, lateral root number of soybean, and measured the soluble protein content and protease activity. In field tests, we used the D. stramonium-soybean intercropping system to study the effects on the yield and quality of soybean. The test results were as follows:1. D. stramonium extracts had allelopathic effects on soybean, which improved with concentration increasing.2. The allelopathic effects differed with donor sites, which were in the order of root > peel > seed. As to receptor, the soybean root growth was more seriously inhibited than germination, especially lateral root growth. High concentration extract make soybean root malformation, manifesting as root bending and asymmetric growth, partly absence of root hair, etc.3. The results of physiological index indicated that D. stramonium, which mainly suppressed decomposition of soybean soluble protein, had lower inhibition effect on of storage protein hydrolysis.4. In fields, companion D. stramonium had inhibitory effects on soybean, which improved with D. stramonium density increasing.5. Low density D. stramonium had no significant effects on soybean yield, but moderate and high density did. Besides, the inhibitory effects on biological yield of soybean were significantly higher than economic yield.6. Low density D. stramonium had no significant effects on soybean quality, but moderate and high density, which remarkably improved crude fat content of soybean, significantly inhibited its 100-seeds weight. Besides, crude protein content of soybean had not been significantly affected by any D. stramonium density set in these tests.7. In preliminary pest risk assessment, we had good reason to believe that, generally speaking, D. stramonium had no highly risk to invade soybean fields.
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