مجله پژوهش علف های هرز
سال دهم شماره 2 (پاییز و زمستان 1397)

Metribuzin is one of the most common herbicides used in potato cultivation. This experiment was conducted to study the effect of soil characterstics and utilization history of metribuzin on its efficiency to redroot pigweed control as factorial on the base of randomized complete blocks design with three replications at Institue of Plant Protection in 2012. First factor was soil type in six levels (Hamedan with 15 years and without utilization history, Jiroft with 15 years and without utilization history, Isfahan with 2 years utilization history and Mashhad with 3 years utilization history) and second factor was different concentrations of metribuzin (0, 100, 300, 700, 1000 and 1500 g ai ha-1). Before cultivating redroot pigweed seed, the pots with mentioned soils were treated with metribuzin and harvesting was done four weeks after cultivating. Then, length and dry weight of shoot and root were measured and dose-response curves were drawn. The highest and lowest damage to redroot pigweed was observed in soils of Jiroft without utilization history and Hamedan with 15 years utilization history, respectively. In Jiroft soil with 15 years utilization history, shoot dry weight reductions were 15, 29, 45, 46 and 56 percent at concentrations of 0.1, 0.3, 0.7, 1 and 1.5 kg ai ha-1 of metribuzin, while in Hamedan soil with 15 years utilization history shoot dry weight reductions in the mentioned concentrations of metribuzin were 6, 11, 25, 31 and 36 percent, respectively. Results showed in different soils, increasing the concentration of herbicide resulted in a more favorable control of redroot, but increasing the amount of clay and organic matter, as well as increasing the history of consumption, affected the severity of the effects of metribuzin residues.

To investigate the effects of cover crop and metribuzin herbicide on weed seed bank of potato in different tillage systems, the experiment was carried out as a split- split plot based on a randomized complete block design with three replications at the Research Station of Agricultural Faculty of Bu-Ali Sina University, 2013. The treatments included tillage systems at two levels (conventional tillage and minimum tillage) as main plots, three levels of cover crop (Vetch (vica villosa roth), barley (Hordeum vulgare L.) and without cover crops) as subplot, and two levels of metribuzin herbicide (with herbicide and no herbicide) as sub-sub plots. The results showed that the application of metribuzin herbicide reduced seed bank density of weeds. Seed bank density of weeds reduced with application of metribuzin herbicide was about 33.62 percent, compared to no herbicide. Application of cover crops in the minimum and conventional tillage reduced seed bank density of weeds 44.43 and 54.88 percent, respectively, compared to no cover crops. The use of barley and vetch cover cover decreased the richness index of seed bank of weeds. Metribuzin herbicide in the minimum and conventional tillage in comparison to control treatment decreased 23.22 and 71.51 percent the richness index of the weed species. Cover crops decreased by 24.60 and 23.13 percent in conventional tillage and minimum indices of Shannon-Weiner weeds. The decrease in the Shannon-Weiner index with application of herbicides and cover crop in the conventional and minimum tillage was 85.17 and 32.66 percent, respectively, compared to no cover crops.

In order to evaluate the herbicides on yield and corn components in different tillage systems in Fasa, an experiment was conducted in split plot in a randomized complete block design with three replications in two years. Main plots consisted of tillage in three levels: common tillage, low tillage and no tillage and subplots were treated with herbicides in 7 levels of Nicosulfuron in 2 concentrations of 2 and 1 liter per hectare, Furamsulfuron in 2 and 1 liter per hectare, formasulfuron + iodosulfuron in 2 Concentration was 1.5 and 0.75 liters per hectare and without herbicide as control. The results showed that the highest weed density was in conventional tillage (7.5 and 5.5 plants / m 2), and the lowest weed density in weed loss was obtained. The highest dry weight of weeds was in conventional tillage (45.3 and 36.1 g / m2), and the lowest dry weight of weeds was obtained in non-topical cultivars. Nicosulfuron at the rate of 2 liters per hectare had the greatest effect on the decrease in grass weed density, and there was no significant difference in reducing the density of broadleaf weeds herbicides among herbicides. Also, nicosulfuron had the highest effect on dry weight loss of grassleaf and broadleaf weeds (22.8 and 13.8 g / m2, respectively). The highest grain yield of corn (12 tons per hectare) was obtained from low tillage and nicosulfuron at 2 liters per hectare and the lowest grain yield (5.6 tons per hectare) was obtained in conventional tillage and non-herbicide control.

In order to evaluate the effect of different management practices on the emergence time of vevetleaf, a split-split plot experiment was conducted in a completely randomized block design with three replications in Dasht-e-Naz Sari in 2016 and 2017. Two tillage systems (Conventional tillage and no-till), three soyabean seeding rates (200,000; 300,000 and 400,000 seeds ha-1), and three doses of imazethapyr (SL 10%) (0, 50, and 100 g ai ha-1) were considered as experimental factors. The velvetleaf emergence was significantly affected by management practices including tillage system, soybean seeding rate, and imazethapyr dose. No-till system, a density of 400 000 seeds ha-1 and a 100 g a.i. ha-1 imazethapyr dose not only resulted in the lowest velvetleaf seedling density m-2 but also caused the longest delay in the time to reach 50% of seedling emergence, thus resulting in a long lag phase of velvetleaf emergence early in the season. Findings from our study may facilitate the development of effective P. oleracea management strategies.

Reduce pesticides usage and improve efficiency of them can be achieved by the technology of controlled release formulations. This experiment conducted to investigate the efficiency of synthesized microcapsule formulation of trifluralin in Tirtash Research and Education Center (located in Mazandaran province, the north of Iran) during the 2014 growing season. The experiment design was three-way factorial arrangement on a CRD with three replications. The treatments consisted of the microcapsule and emulsifiable concentrate (Treflan® 48%) formulation in different doses, 50, 75 and 100 percent of recommended dose (0.6, 0.9 and 1.2 kg a.i./ha) and application methods, soil-incorporated pre-planting and pre-planting. Weeding and weed infest were prepared as control plots. Density and dry weight of weed at 40 and 60 days after tobacco transplanting and tobacco yield were measured during the growth season. Based on the relative abundance of weeds, Setaria viridis L. and Amaranthus retroflexus L. were dominant species. The experimental results show there were significant difference between formulation type, dose and method of application on density and dry weight of weed and tobacco yield. The effectiveness of MC formulation in each applied dose were higher than EC formulation. The 50% recommended dose of MC formulation had the same weed control effectiveness as 75% recommended dose of the EC formulation. The green foxtail and redroot pigweed control were about 72 and 69% in 50% recommended dose of MC formulation and about 79 and 65% in 75% recommended dose of EC formulation, respectively. Also 50% of MC formulation could increase yield as same as the 100% of EC formulation, 4.26 and 4.30 ton.ha-1, respectively. Soil incorporation of trifluralin was very necessary to achieve best efficiency.

To evaluate the population and diversity of weeds in wheat fields in Qazvin, Iran, an experiment was conducted during 2015-2016 growing season. A net sampling method was employed to take samples from 9 fields of 3-hectar area which were managed either in dry farming, no-tillage, or irrigated systems. Samples were taken at two growing stages when wheat plants were at tillering and when they reached full stem growth stage. The highest population and diversity of weeds was observed in dry farming system and the lowest was seen in irrigated system. The frequency of weed population was lowest in no-till system. The highest grain yield (6231 kg/ha) and total dry matter (18580 kg/ha) was measured in irrigated system, and the lowest grain yield (2078 kg/ha) and total dry matter (60180 kg/ha) was obtained in dry farming system, respectively. Based on the low weed population and a grain yield of 5830 kg/ha in no-till system, it seems that this production system is economically and environmentally justifiable for wheat production in Qazvin Provence, Iran.