IRANIAN JOURNAL OF WEED SCIENCE
Year:2016 | Volume:12 | Issue:1 |Papers Count:8

In order to study the effect of reduced doses of oxadiargyl, on weeds control in potato, a field experiment was conducted at Alaroog Research Station in Ardabil during 2013. Experiment arrangement was factorial based on randomized complete blocks design with three replications. First factor included seven reduced dosages of oxadiargyl (0, 0. 05, 0. 1, 0. 2, 0. 4, 0. 6, 0. 8 L a. i/ha) and second factor included oxadiargyl application timing (potato emergence, stoloning and tuber bulking). The results showed that application of 0. 8 L a. i/ha of oxadiargyl reduced weed density and biomass to 48. 40 and 66. 16 percent, respectively which was not significantly different from applying 0. 6 L a. i/ha. Maximum reduction percentage of weed density and biomass on the different potato growth stages was at potato emergence stage, which provided the best effectiveness of the oxadiargyl. On the other hand, application of 0. 8 L a. i/ha oxadiargyl at potato emergence stage caused the highest mean of tubers weight per plant and total tuber yield, but was not significant on the tuber number per plant.

In order to determine the critical period of weed control in sunflower (Helianthus annuus L. cv. Sandra) a field study was conducted in the Mobarakeh region during 2013. The experiment was carried out in a randomized complete blocks design with three replications. Treatments were based on the days after emergence of sunflower in two series. The first series consisted of weed removal, 10, 20, 30, 40, 50 and 60 days after sunflower emergence and then weed maintained until harvest. The second series consisted of weed maintaining till mentioned stages and then weed removal until harvest. Also, two control treatments (weed free and weed infested for all of the growth season) were applied. Results showed that with increasing period of weed interference, grain yield, oil yield, seed number per head and 1000 seed weight decreased significantly. Increasing period of weed control, above characteristics increased significantly. Increasing period of weed interference, weed dry weight significantly increased, but weed density first increased and then decreased. With increasing period of weed control, weed dry weight and density significantly reduced. Considering 10% acceptable grain yield losses, the critical period of weed control of sunflower was determined to be 12-40 days after emergence (between 4 leaves and flowering stage).

In order to investigate the critical period of weed control in sugar beet, an experiment was conducted during 2011-2012 in the experimental fields of Agricultural-Jihad training center of Qaen, . The experiment was conducted in a randomized complete blocks design with four replications using two series of different combinations of weed free and weed interference periods along with weedy and weed free checks as control. The first set of treatments were weed interference periods of 2, 4, 6, 8, 10 and 12 weeks after sugar beet planting, and the other set included weeding periods of above periods. Results showed the critical period of weed control based on 5, 10, 15, and 20% acceptable root yield reduction ranged between 10-106, 16-80, 24-78 and 31-70 days after planting, respectively. A critical period of weed control for extractable sugar was observed to be 8 to 112, 14-95, 22-82 and 29-74 days, after planting, respectively. The results showed significant difference between interference and weed free treatments on root yield extractable sugar, as well as weed dry weight. There was no significant difference for potassium content of sugar beet root among weed interference treatments, while it had significant difference among weed free treatments. In the results of this experiment the beginning of critical period control of weeds is 10 to 31 days and the end 70 to 106 days after planting.

In order to evaluate the effects of sulfosulfuron application on morphological and reproductive traits of Iranian wild barley populations at two leaf and second node stages, an experiment was performed in Varamin region during 2013 and 2014 in the form of factorial randomized complete blocks design with four replications. The first factor included two levels of sulfosulfuron applications at two leaf (GS =12) and second node (GS = 32) stages of barley growth, and the control treatment was without herbicide. The second factor consisted of wild barley 20 populations, which were collected from across the country. Results showed that application of herbicide at above stages caused significant effects differences in terms of reduction of growth and reproduction of wild barley, but the use of herbicide at the second node stage was more effective. Populations showed differences in view of morphological and reproductive traits in response to herbicide treatments. Thus, the effect of herbicide on morphology and reproductive traits of Varamin, Isfahan, ShahReza and Golpayegan populations was the lowest, while on Shoush, Ramhormoz and Fasa populations was the highest.

Considering the importance of conservation tillage and reduction of herbicide in the sustainable management of agricultural systems, use of cover crops can be considered as an alternative or supplement to control of weeds. A field experiment was conducted at the Research Station of Agricultural Faculty, of Bu-Ali Sina University, in 2013. The experiment was carried out as a split-split plot based on a randomized complete blocks design with three replications. The treatments included tillage systems at three levels (conventional tillage, minimum tillage and no-tillage) as main plots, three levels of cover crop (Vetch (vica villosa Roth), barley (Hordeum vulgare L. ) and without cover crop) as subplot, and two levels of integrated control of weeds (weed control and weed free) as sub-sub plots. Barley and vetch cover crops combined with integrated weed control in conventional tillage system could completely control the weeds. Application of cover crops in the conventional tillage, reduced tillage and no tillage systems reduced Shannon-Wiener diversity index of weeds by 54. 24, 33. 78 and 54. 84 percent, respectively. Reduction rate of diversity index using integrated control in the conventional tillage, reduced tillage and no-tillage systems compared to the control by 66. 66, 61. 74 and 56 percent, respectively. The highest tuber yield (63. 74 Tons per hectare) was obtained in conventional tillage system application with vetch cover crop combined with integrated weed control that was about 55. 81% more than that of no integrated weed control and no cover crops application, treatment.

To study effects of nicosulfuron herbicide in soil on wheat, barley and rapeseed after corn harvesting, a field experiment was conducted at the research fields of Ferdowsi University of Mashhad, Iran. The experimental design was arranged in completely randomized blocks design with factorial arrangement of treatments with three replications. The factors included organic fertilizers at 4 levels (cow manure at 40 tons ha-1, vermicompost at l0 tons ha-1, 250 g m-2 mycorrhiza and control treatment without fertilizer). Nicosulfuron (Cruz® , 4% SC) rates included 40 and 80 g ai ha-1, with and without the adjuvant (HydroMax™ ) at 0. 5% (v/v). Each plot was divided into two halves with and without the herbicide application, in the corn farm. After harvest of corn, each plot was divided into three longitudinal sections and canola, wheat and barley were planted in each section. Results indicated that plant height, number of ears or silique per square meter, number of seeds per ear or silique, 1000-grain weight, shoot biomass and grain yield of rapeseed, wheat and barley significantly reduced when herbicide was applied at recommended dose. The addition of HydroMax with nicosulfuron, reduced aboveground biomass of mentioned crops, significantly. While organic matter decreased herbicide residue of nicosulfuron and increased plant growth. However, the highest seed yield and the lowest percentage of damage were 63, 419 446 g m-2, and 33%, 23%, 28% in rapeseed, wheat and barley respectly, when cow manure was used plus nicosulfuron at 40 g ai ha-1. In this study, crops sensitivity to soil residue of nicosulfuron herbicide in soil was ranked as rapeseed> barley> wheat.

The information of the genetic diversity of weed community helps researchers to find more effective biological control methods. In the present study the genetic diversity within and between populations of distaff thistle (Carthamus lanatus) was investigated using 24 ISSR markers. The populations were collected from eight different regions of Golestan province. Using 9 polymorphic (26. 4 %) ISSR markers, the mean coefficient of similarity between individuals based on Jaccard, and descriptive parameters such as Nei’ s gene diversity, Shannon's information index, percentage of polymorphic loci, observed number of alleles (na) and effective number of alleles (ne) were calculated for each population. The highest genetic similarity coefficient was observed in the ecotypes collected around Gomishan and the lowest occurred in ecotype Bandartorkman. Analysis of molecular variance showed that the genetic diversity among populations (63 percent) was higher than genetic variation between populations (23 percent). The highest values for Nei’ s gene diversity, Shannon's information index, percentage of polymorphic loci, observed number of alleles, effective number of alleles was observed in ecotype Bandartorkman and the lowest values of these parameters occurred for ecotypes Ashuradeh Island and Inchehbroon. Therefore, ecotype Bandartorkman had the highest, and ecotypes of Ashuradeh Island and Inchehbroon the lowest within population genetic diversity.

In order to investigate genetic variation of Hordeum spontaneum C. Koch populations in Iran, an experiment was conducted at the research section of the Department of Agronomy and Plant Breeding, University of Tehran from 2013 to 2014. In this study, 40 ecotypes of H. spontaneum collected from all parts of Iran were investigated by means of 11 SSR markers. Results revealed that the number of polymorphic bands for each primer varied from 2 to 14, on average, 7 and 5. 6 polymorphic bands for all primers. Total variances observed were related to diversity among and within the populations which were 48% and 52% respectively. This means a high differentiation among the populations. The biotypes of wild barely (40) were divided into 5 groups including: A: Fars populations, B: populations of Yazd, Chaharmahal va bakhtiari, Lorestan, Ilam and Hamedan populations, C: Qazvin, Alborz, Khomein, Qom and Khorasan populations, D: Kurdistan, West Azarbaijan, Lorestan, Ardebil and Qazvin populations. E: Hamedan, Kurdistan and Kermanshah populations. The placement of closed area populations in one group may be due to penetrations into each other, through farm machinery or cultivated crop seeds. The hypothesis of seed transport from Fars province to far areas such as Karaj and Varamin is rejected. Knowledge of the genetic diversity of this weed, can lead to development of management plans in order to effectively control this weed especially in wheat fields.