The critical period of weed control in winter canola (Brassica napus L.)

摘要

In order to determine the critical period of weed control in winter canola (Okapy Double Zero), an experiment was carried out at research field of Tarbiat Modarres University (placed in Tehran west, Iran) on 20042005 growing season. Randomized complete block design with 4 replications were used. Fourteen treatments divided into two sets. In first set of treatments, the crop was kept weed-frww until 2, 4, 6 and 8 leaves, inflorescence emergence, 50% silique appearance and harvest stage. In second set of treatments, weeds were permitted to grow with the crop until above mentioned stages. In this study the critical period of weed control was determined based on natural population of weeds which emerged from soil seed bank. Results showed a critical time 5% accepted yield loss. Therefore weed control of weed control in 25 days after emergence (between four and six-leaf stage) within this time could provide the best result and reduced the rapeseed yield loss.