The mixing of barley grain with volunteer wheat grain causes a serious problem in wheatsoybean-barley rotation. This report describes the relationship between the persistence of volunteer wheat and the mechanical weeding method in soybean culture. Control of volunteer wheat by inter-cultivation and ridging in soybean fields was effective. During the summer, most volunteer wheat plants died from drying or burying.
Inter-cultivation and ridging had killed wheat grain and wheat seedlings at a soil layer of 0-6cm deep. So when inter-cultivation and ridging were used in the cultivation of soybean, volunteer wheat decreased in fields where barley were planted by no tillage. But when inter-cultivation and ridging were also used in the cultivation of soybean, volunteer wheat increased in fields where barley were planted by rotary tillage. The reason why volunteer wheat increased in this field was that the wheat grain at a soil layer of 7-15cm deep was moved to suitable depth of emergence by rotary tillage.
In wheat-soybean-barley rotation, the best means were to prevent the mixing of barley grain with volunteer wheat grain by the combination of inter-cultivation with ridging in the cultivation of soybean, and by no tillage in the cultivation of barley.
