Research on establishment and control of exotic weeds-the weed in forage crop fields : Velvetleaf-

丝绒叶（Abutilon theoprasti Medicus）是一种外来的一年生杂草，由于其适应性强、多产且难以控制，经常成为日本饲料作物田的优势杂草。在日本西南部，棉叶在玉米地里越来越普遍。目的是确定棉叶的生理和生态特性，并制定一个成功的棉叶管理方案。通过田间试验，研究了不同密度和不同播期对玉米生长和产量的影响。玉米出苗后10天出现丝绒叶对玉米生长和产量没有影响。虽然高丝绒叶密度会降低玉米的生长，但由于抑制了分枝，丝绒叶比低丝绒叶密度下产生的种子更少。杂草型天鹅绒叶在分枝、种子大小和高产率等方面表现出与栽培型不同的性状。新鲜种子休眠程度高，棉叶种子需要3个月才能打破休眠。去年土壤中棉叶种子数量与田间植物数量成正比。有耕作的栽培处理比不耕作的处理能更快地打破丝叶种子的休眠。

Velvetleaf (Abutilon theoprasti Medicus) is an exotic annual weed, and often becomes a dominant weed at forage crop fields in Japan because it is adaptive, prolific, and difficult to control.In southwestern part of Japan, velvetleaf is becoming more prevalent in corn fields.The objectives are to determine the physiological and ecological characteristics of velvetleaf, and develop a successful velvetleaf management program in corn fields.Field experiments were conducted to study the effect of varying velvetleaf densities and planting dates on the growth and yield of corn.Velvetleaf emerging 10 days after corn emergence did not reduce corn growth or yield.Though corn growth reductions caused by high velvetleaf densities, velvetleaf produced less seeds compared with at low velvetleaf densities because of inhibiting branching.Weedy type of velvetleaf exhibited different characters from cultivation type in view of branching, seed size and high seed output.Fresh seeds exhibit a high degree of dormancy, and it needs for 3 months to break dormancy of velvetleaf seeds. Velvetleaf seeds population in the soil was directly proportional to the plant population in fields last year.Cultural treatments with tillage practices caused faster breaking velvetleaf seed dormancy than those without tillage.