جستجوی مقالات مرتبط با کلیدواژه « اختلاط » در نشریات گروه « زراعت »

Xanthium strumarium (Cocklebur) is a genus of flowering plants in the family Asteraceae, native to the America, Eastern Asia, South Africa and Australia. It is coarse, herbaceous annual plant growing to 50-120 cm tall, which invades agricultural lands. Its seedlings and seeds contain the glycoside carboxyatractyloside and can be poisonous to animals, including cattle, horses and pigs. Its successful spread in so many parts of world has mainly attributed to its allelopathic properties, which enable it to complete effectively with native crops and/or pasture species. Vigna radiata is an important food legume cultivated in rainfed areas in the west and northwest of Iran. One of the main reasons of its lower yield is competition from weeds, because it does not compete well with weeds. Thus, weeds reduce yield and quality of mungbean through competition for light, moisture and nutrient. This study was aimed at determining the possible effects of the widespread weed X. strumarium L. whole plant A.E. on germination and seedling growth of mungbean under laboratory and greenhouse conditions.

Naturally growing common cocklebur plants around our university campus were randomly uprooted and collected during flowering stage in August 2018. The plants were immediately brought to laboratory and the whole plant cut into 2 to 3 cm pieces, air-dried in greenhouse and ground in a mill of 2 mm sieve size. Then 3, 6 and 9 g of ground materials were mixed in 100 ml distilled water and soaked for 24 h at room temperature (21 to 22 oC) and filtered through four layers of cheesecloth. The aqueous extracts were stored in conical flasks in dark until use. Both in laboratory bioassays or greenhouse studies were done from August to December, 2018 and the rates of 90, 180 and 270 g powdered material or 3, 6 and 9% extracts were based on the previous studies.  

Results showed that mean rate of germination in control treatment was higher than that of other treatments, but there was not any significant difference between control and 3% treatment. The lowest value for this trait belonged to aqueous extract i.e. 9%. The increase in X. strumarium L. A.E. concentration was concomitant with decrease of the mean rate of mungbean seed germination. In this case, there was a negative linear regression between A.E. concentration and plumule length as well. It is noteworthy that decrease in germination rate led to a delayed emergence and poor establishment of mungbean seedlings. X. strumarium A.E. did not adversely influence plumule dry weight of mungbean in the 3% A.E. treatment, compared to the control. The A.E. concentrations of 6 and 9% resulted in significant reduction of 20.87 and 30.97% in plumule length compared with those of the control, respectively. The soil incorporation of dry mix residues decreased both germination and seedling growth of mungbean. There was an increase in inhibitory effect with increase in amount of dry residues incorporated. However, no significant difference was observed between control and 90 g for both germination (%) and rate, and root and shoot lengths. Compared to soil incorporated dry mix residues, the soil surface applied dry whole plant residues drastically inhibited the mungbean germination and seedling growth. This is congruent with previous report. All rates of soil surface placed X. strumarium dry mix residues significantly inhibited the mungbean seedling emergence (%) and rate and root and shoot lengths over the control. 

High concentrations of X. strumarium L. A.E. negatively influenced seed germination rate, plumule length and seedling dry weight of mungbean. However, their effects were not considerable at low concentrations. In conclusion, we can claim that mismanagement of weed population in field condition especially high densities of X. strumarium L. weed and presence of high concentrations of water soluble chemicals produced by this weed adversely influence early growth (delayed emergence and dwarf and weak seedlings) of mungbean plants. Eventually, this trend negatively influences homogenous emergence of plants and the result would be plants susceptible to biotic and abiotic stresses, leading to very low marketable yields.

The efficacy of pretilachlor from chloroacetamide herbicides inhibiting lipid synthesis and bensulfuron from sulfonylureas urea inhibiting the synthesis of enzyme acetolactate synthase in the control of barnyardgrass and bulrush were investigated in sole and mixed applications at 0, 25, 50, 75, 100 and 125% of the recommended doses. The results showed that weed control in response to different doses of two herbicides could be expressed by logistic dose-response model (R2≥95%). The required dose for 50% reduction of barnyard grass biomass (ED50) in the treatment with pretilachlor and bensulfuron was 17.1% and 24.7% of the recommended dose, respectively, and 32.3% and 26.4% of the recommended dose for bulrush respectively, indicating higher efficiency of pretilachlor in barnyardgrass and bensulfuron in bulrush controls. While pretilachler provided complete control of barnyardgrass, none of the herbicides were able to completely control bulrush up to 125% of the recommended dose. According to the fitted dose response logistic model (R2≥95%), mixing the recommended doses of bensulfuron with 75% of recommended dose of pretilachlor or the recommended dose of pretilachlor with 25% of recommended dose of bensulfuron resulted in 100% control of bulrush. Today, sedges are the most abundant and diverse weeds in rice fields, and according to the results of this study, to control the most prevalent weed of this group, bulrush, mixing of herbicides is necessary. By mixing the pretilachlor and bensulfuron herbicides, it is possible to control bulrush and barnyardgrass, the two key weeds of paddy, with lower doses of these herbicides, which require further studies in field conditions to determine the appropriate dose.

Pondweed is a waterlogging habitat weed of paddy fields margin which has recently invaded rice fields. Because barnyardgrass is the most abundant and important weed of paddy fields in Iran, hence adopting any program for pondweed chemical control should involve barnyardgrass control as well. Therefore, two separate trials were carried out to evaluate the efficiency of selective rice herbicides for managing both pondweed and barnyardgrass. In this experiment the treatments included applying thiobencarb (2500 g.ai.ha-1), butachlor (1800 g.ai.ha-1), oxadiargyl (105 g.ai.ha-1), pretilachlor (1000 g.ai.ha-1), bensulfuron-methyl (45 g.ai.ha-1), cinosulforun (45 g.ai.ha-1) and metsulfuronmethyl (10 g.ai.ha-1). In the first trial, each herbicide was applied separately. In the second trial herbicides were mized. Results showed that thiobencarb, butachlor and pretilachlor were effective on barnyardgrass control (≤95%) but had no effect on pondweed. Oxadiargyl was more effective on barnyardgrass (75-90%) than pondweed (35-45%). Sulfonylurea herbicides showed very good efficacy on pondweed control (≤95%) while low effect on barnyardgrass (≥35%). The second experiment was carried out in order to investigate the mixture compatibility of the two groups of herbicides with different weed control spectrum. Data of the second trial confirmed the results of the first trial and revealed that mixing the recommended dose of herbicides controlled both weeds by 95%.

In order to study the possibility of tank mixing of 2،4-D plus MCPA and clodinafop propargyl in wheat fields in Iran، some experiments were conducted in 2003 and 2004. Field experiments were conducted in 2003 as a randomized complete block design with a factorial arrangement of treatments and four replications in Meybod and Oromieh. One of the experimental factors was 2،4-D plus MCPA at 0، 975، and 1300 g a. i. /ha، and the other one was clodinafop propargyl at 0، 64، 80، 96، and 112 g a. i. /ha. In greenhouse experiment، the same treatments were conducted in Iranian Plant Protection Research Institute Greenhouses. Weed floras included winter wild oat (Avena ludoviciana Dur.)، mouse barly (Hordeum murinum L.) and canary grass (Phalaris minor Retz.) in Meybod، cereal rye (Secale cereale L.)، winter wild oat and downy brome (Bromus tectorum) in Oromieh and winter wild oat، canary grass and ryegrass (Lolium perenne L.) in greenhouse. Results indicated that clodinafop propargyl could control winter wild oat and canary grass at the recommended dose (64 g a. i. /ha). Tank mixing of 975 g a. i. /ha 2،4-D plus MCPA with clodinafop propargyl reduced efficacy of clodinafop propargyl at the recommended dose (64 g a. i. /ha). But increasing the dosages of clodinafop propargyl to 112 g a. i. /ha could omit the antagonistic effects of 2،4-D plus MCPA. Tank mixing of 1300 g a. i. /ha 2،4-D plus MCPA and clodinafop propargyl was not satisfactory indicating that this dose of 2،4-D plus MCPA should not be applied with Clodinafop-propargil.

Field studies were conducted in 2005 to determine the effectiveness of different combinations of selective herbicides for control of broadleaf weeds in sugar beet fields in Tehran (Karaj), Khorasan Razavi (Mashhad) and Western Azarbayejan (Miandoab) provinces. Weed biomass and frequency and visual evaluation of weed injury and Sugar beet yield were those traits evaluated in this experiment. Weed biomass and frequency measurements in each province indicated that (phenmedipham + desmedipham + ethofumesate) + triflusulfuron methyl was the best composition. triflusulfuron methyl + desmedipham also was another composition that produced a good result. These treatments had no good effect on bindweed. The least herbicidal effect came from chloridazon + triflusulfuron methyl and chloridazon + (phenmedipham + desmedipham + ethofumesate) which had little effect on weed biomass and frequency.