Study On The Occurring Characteristic Of Weeds And The Method Of Weed Control In Alfalfa Seed Product Field

Weeds are one of the critical factors that affect quantity and quality of alfalfa seed in the course of alfalfa seed production. Weed species, germination ,seed bank in soil and seed vigor were studied in alfalfa seed-producing field of different utilized years. There were two germination peaks in the utilized first year field. The first peak was composed of annual spring weeds; the second was composed of both annual spring weeds and annual summer weeds. The number of annual weeds presents increasing, descending and stabilizing trend in the utilized second year field. The annual summer weeds determine the peak in the utilized third year field. The seed vigor and the number of active seeds in 0?cm layer of soil are higher than those in 5~ 10cm layer. The number of active seed and their vigor in August is lower than those in March. The main reason that leads to decline is weed control and improvement of alfalfa competition.The method of weed control in different utilized year field was suggested in this research. The managing technique of weed control in the utilized first field was established by using Pendimethalin combiningwith shallow intertilling and raining after germinating, artificial control for weeds that still survive and germinate was carried on once or twice, and other perennial weeds and Convolvulus arvensis were sprayed Butoxone along the alfalfa line. The best managing method in the utilized second year and third year field was established by Trifluralin or Pendemethalin combining with harrowing or Pendemethalin combining with shallow intertilling in the early days of germination, the intertilling was carried on in the last of April in order to control annual and perennial weeds, Butoxone may control Com:olvulus arvensis.