Determination of the Critical Weed Control Periods of Okra (Abelmuschus esculentus L.)

To study the effects weed competition periods on fruit yield and yield components of Okra and some of its morphological traits, a completely randomized design experiment with 12 treatment and 13 repetitions was carried out at the Research Fields of College of Agriculture of Birjand Branch, Islamic Azad University, in 2016. The plots consisted of the control (free of weeds until 4, 6, 8, 10 and 12 weeks after okras growth) and the treatments competing with the weeds within the same periods as mentioned above. Also, two separate plots were designed one for complete weed control during whole growth period and in the other weeds were allowed to compete with okra during the growth period, in order to compare the effects of weeds on okra. In the first group the plots were weeded during periods the mentioned above and in the other weeds were let to compete with okra. In the second group weeds competed with okra from the beginning of the growth period to 4, 6, 8, 10 and 12 weeks after germination. There after weed were controlled up to harvest time. The results showed that by increasing competition periods of weeds morphological traits of okra like plant height, main stem branche numbers, fresh fruit length and its diameter, as well as the number of fresh fruits per m^-2, fresh fruit and dried fruit yields, biological yield and dried fruit harvest index per plant, dry weight of broad and narrow leaved weeds, and the percentage of dry fruit yield as compared to that of control treatment were significantly decreased. Based on 5 and 10 percent reduction in fruit yield, starting days of critical weed control period was determined to be 29 and 30 days after seed germination. Thus, it can be concluded that the critical weed period, in terms of okra yield in regard with the mentioned levels, was estimate to be 77 and 80 days after seedling emergence. Therefore, it is recommended that from the 29th to 80th day after seedling emergence of the okra, the field ought to be free of weed.