Predicting the Emergence of Weeds of Bermuda grass (Cyndon dactylon L.) and Purple nutsedge (Cyperus rotundus L.) in Canola Under Different Management Operation

Perennial weeds live at least 2 years; some live for decades. Most perennial weeds reproduce both by seeds and by the spread of energy-storing vegetative parts, such as roots or tubers. Strict winter weeds have the ability to survive and grow during times of the year when environmental conditions, mainly temperature, are not favorable for the development of other plant species. The objectives of this research were to understand the role of soil temperature in the emergence of bermuda grass and purple nutsedge in canola and to develop predictive models for the emergence of these two weeds based on soil thermal time (STT) accumulation. In order to predict the emergence pattern of bermuda grass and purple nutsedge under different management operation, a split plot experiment was conducted in a completely randomized block design with three replications in Sari Agricultural College in 2022. Two tillage systems (Conventional tillage and no-till) and three doses of Butisan Star (quinomerac + metazachlor) (0, 50, and 100 % recommended dose) were considered as experimental factors. To predict emergence pattern in each plot a fixed quadrat 50 in 50 cm in the center of each plot was and the start of the season after the first irrigation, new seedlings grown count, based on the species began. A three-parameter logistic model was used to describe the cumulative seedling emergence (CE) with STT. Parametric estimates were compared using paired t-test (P<0.001). From the emergence count data, mean emergence time (MET) and emergence rate index (ERI) were calculated. Comparing the average values of MET and ERI indices were compared by SAS 9.2 software and using LSD test. Bermuda grass in the no-till (NT) system and purple nutsedge in conventional tillage (CT) system had a shorter mean emergence time (MET) and a higher emergence rate index (ERI), and by receiving a lower growing degree days (T50), they reached 50% of their cumulative growth faster. Also, bermuda grass and purple nutsedge at the the highest dose of Butisan Star (100 % recommended dose) had the highest MET and the lowest ERI, and by receiving higher T50 and having a lower emergence rate (Erate), they achieved 50% cumulative emergence of seedlings later. Purple nutsedge in both tillage systems and all three doses of Botisan Star herbicide had a lower MET compared to bermuda grass and by receiving lower T50, it achieved 50% cumulative seedling emergence faster at the beginning of the growing season. On this basis, growth stage suitable for controlling purple nutsedge, when the main wave of bermuda grass seedlings still have not found emergence.