Introduction: The occurrence of continuous drought and water crises in arid and semi-arid regions of Iran, including the Lake Urmia catchment area, has necessitated changes in the agricultural system to cope with the water scarcity. Any modification in the agricultural system can impact all the ecosystem components, including weeds. Weeds grow at the same time as sugar beet and accompany it during its growth period. Sugar beet is one of the crops that suffers the most damage from the presence of weeds in the fields. Weeds can significantly reduce sugar beet yield and efficiency. Nitrogen fertilizer can be an effective way to decompose plant residues. Therefore, the aim of this study is to investigate the effects of cultivation arrangement, planting method, irrigation regime, and nitrogen fertilizer with and without mulch in tape irrigation on weed populations and different elements of sugar beet roots in the catchment area of Lake Urmia, which has the largest area under sugar beet cultivation in Iran.
Materials and Methods: The study area is located 7 km south of Bukan city, which is part of the catchment area of Lake Urmia. The experiment was conducted during the 2018-2019 cropping season as a factorial design based on a randomized complete block with three replicates. The first factor was the use or non-use of mulch, and the second factor included different types of tape arrangements and cultivation rows (50x50, 40x50, 40x60, 50x50x50), different cultivation techniques (seedling planting and an arrangement of direct seeding (50x50x50)), irrigation regimes (75% and 100% full coverage irrigation in the 40x50 arrangement), and the use of nitrogen fertilizer (at three levels in the 40x50 arrangement). At the end of the growth period, the crops from each plot were harvested and screened. After washing, 150 grams of root pulp were prepared, frozen, and sent to the laboratory to determine some quality characteristics. Weed control in seed cultivation was carried out in two stages during the growth period and in both years, with the first stage taking place 45 days after planting, simultaneously with planting, and the second stage 30 days after planting by hand weeding. The first round of manual weeding of weeds in the plantation was done at the same time.
Results and Discussion: The results indicate that mulch did not have a significant effect on weed populations at a 5% level of significance. However, the planting method, either direct sowing or seedling transplantation, had a significant effect on weed populations at a 5% level of significance in both years. The average number of weeds in seed cultivation was 55% higher in the first year and 54% higher in the second year compared to seedling cultivation, even though seed cultivation was performed 45 days later than the area cultivation time. The amount of Alpha-Amino-Nitrogen and sodium in sugar beet roots was 2.1 and 2.5 times higher in seed culture in the first year, and 2.1 and 3 times higher in the second year, respectively. In the case of 25% reduced irrigation, the average Alpha-Amino-Nitrogen and sodium in sugar beet roots increased by 8.6% and 39% in the first year and 8.5% and 35% in the second year, respectively, compared to full irrigation.
Conclusion: Considering the environmental and economic benefits of reducing weeds in sugar beet cultivation, using the two-row arrangement method (40x50, 40x60, and 50x50) is recommended as an effective alternative to direct sowing. This method was found to significantly reduce weed populations compared to direct sowing, leading to reduced use of harmful pesticides and lower labor costs in organic production. Additionally, the two-row arrangement method may offer other benefits such as improved water and nutrient management, although it may require more precise planting and irrigation practices. Further research could investigate the potential drawbacks and benefits of this method in different soil and climate conditions.