Studies on the duration of annual weed competition on sugar beet

The effect of duration of annual weed competition on sugar beet yield was determined during 1990-1992 in Zarghan and Fassa regions, Fars – Iran. A randomized complete block design (RCBD) with 7 treatments in 4 replications was used. Each plot consisted of 6 rows, 10 meters long and 61 cm distance between rows. The treatments were the following:  1- One hand-weeding at 5 weeks after planting  2- One hand-weeding at 8 weeks after planting  3- One hand-weeding at 10 weeks after planting 4- Two hand-weeding at 5 and 8 weeks after planting  5- Three hand-weeding at 5 and 8 weeks after planting 6- weed-free for the whole period of growth 7- Weedy for the whole period of growth. The results showed that sugar beet yield was highly affected by the duration of weed competition. The weed-free plots yielded 30% and 62% more than the weed plots, for Zarghan and Fassa, respectively. Maximum yield was obtained when sugar beet field was hand-weeded for the whole period of growth. However, there was no significant difference between the weed-free plots for the whole season and the two other periodically hand-weeded plots (either two times at 5 and 8 weeks after planting or three times at 5, 8 and 10 weeks after planting). It is concluded that two hand-weedings  at 5 and 8 weeks after sugar beet planting are enough to have and acceptable yield under the conditions of these experiments.