جستجوی مقالات مرتبط با کلیدواژه « نقشه علف های هرز » در نشریات گروه « زراعت »

In order to identify weedspeciesand their community structure in saffron fields of Kashmar and Khalil-Abad counties, 45 farms were selected randomly based on cultivation area during 2014- 2015. In each farm weed species were counted separately and also the geographical information of each farm was recorded by GPS. These data were used for mapping of weed species and geographic distribution in ArcGIS software. The results showed that 82 weed species belong to the families of Astraceae, Brassicaceae, Poaceae and Caryophyllaceae had the highest frequency, respectively. The most important weeds in the surveyed area based on the abundance index were: downy brome (Bromus tectorum L.), Hordeum spontaneum C. Koch, from grasses and hoary cress (Cardaria draba (L.) Desv.), Holosteum glutinosum F.et M, Russian knapweed (Acroptilon repens (L.) DC), Sisymbrium subulatum E.Fourn , creeping thistle (Cirsium arvense (L.) scop) from Broad leaves. Annual weeds had the greatest species diversity (53 species), biennial weeds had the lowest species diversity (4 species), and perennial weeds were intermediate (25 species). 82 percent of weeds were broadleaf, and 18 percent were narrow leaf weeds. The weeds such as Bromus tectorum L., Holosteum glutinosum F.et M, Acroptilon repens (L.) DC, Descurainia sophia (L.) Schar, and Cardaria draba (L.) Desv., were dominant species in Kashmar, while Cardaria draba (L.) Desv., Hordeum spontaneum C. Koch, Sisymbrium subulatum E.Fourn, Hordeum murinum L., Cirsium arvense (L.) scop, and Malcolmia africana (L.) R.Br., were dominant species in Khalil-Abad . Cardaria draba was problematic and dominant species at both locations.

To evaluate the effect of crop rotation on spatial dynamic of Fumaria vaillantti and Polygonum aviculare a study was conducted at the three farms with different rotation in the Astan Ghods Razavi filed that located at 10 kilometers southeast of Mashhad, Iran. The rotations were alfalfa- fallow- wheat, canola- fallow- wheat, and wheat- fallow- wheat. At the crosses of 7×7 m quadrangular grids network, discrete systematic sampling was performed using 0.5×0.5m quadrates at three stages including before chemical control, after chemical control, and before harvesting and density of weed species were recorded separately. In each three rotations Fumaria vaillantti and Polygonum aviculare were part of dominant species at second and third sampling stages, But at the first sampling stage dominant species were different. Polygonum aviculare was became dominant species at the third sampling stage, Mean while, the importance of Fumaria vaillantti were reduce. Bing winter Fumaria vaillantti and summer Polygonum aviculare can be the cause of this phenomenon. Variogram parameters survey show that the minimum and maximum of nugget effects for studied species was 0.17 and 1.001 respectively. The range of weeds in field varied between 2.8 – 93.5m. Nugget effect and range were downside at each three rotations and at during of first and second sampling, while nugget effect and range variations of Fumaria vaillantti were different depend on rotation type. The distribution maps of studied weed were drawn after applying varigram parameters in Kriging method that showed patchy and plow directed distribution. Our Results showed that crop rotation and cultural operation effects dynamism of the weeds, that Knowledge of these effects can be an opportunity for more effective weed control.

In order to evaluate the spatial dynamic of weeds during growing session an experiment was conducted at Astane Ghodse Razavi experimental field. One hectare size with canola-fallow-wheat rotation was selected. Sampling was carried out by discrete systematic method in which the samples were taken from plots of 7m×7m, using 0.5m×0.5m quadrates in three stages, pre chemical control, post chemical control and pre harvesting, and species and their densities were determined. Fifteen species were observed from 196 sampling points. Total weed density in the field during the first, second and third sampling stages were 44.42, 12.16 and 3.93 plant per square meter respectively. It seems that this downward trend was as a result of control operations efficiency. Goldbachia laevigata and Chorispora tenella were most important weeds in the filed during first sampling stage. While Fumaria vaillantii and Polygonum aviculare became important at during the second stage of sampling. Also P. aviculare was the most important weed in the filed during the third sampling stage and the importance of F. vaillantii was decreased. To describe the dynamics of weeds, the geostatistic method was used and variogram functions of weeds in each three sampling stages were calculated which had spherical and exponential models. Maximum and minimum of nugget effect were 0.13 and 0.45 respectively. The ranges were also between 2.8 and 196.6m. The spatial distribution maps of weeds were drawn applying variogram parameter in Kriging interpolation that showed patchy and plow directed distribution. The results showed that presence of canola in crop rotation and corresponding control operations was effective on type and spatial distribution of weeds of studied species. In fact crop rotation with the effects on weed communities can be as an option in integrated weed management effect on weeds.

Crop type and management practices during rotation influence the spatial distribution and dynamics of weeds. The present study was conducted in order to evaluate the spatial distribution pattern and weed dynamics in Astane Ghodse Razavi experimental field. One hectare size field with Alfalfa- Fallow- Wheat rotation was selected, sampling was carried out by discrete systematic method in which the samples were taken from the intersection of 7 m* 7m grids using 0.5 * 0.5 m quadrates in three stages, pre chemical control, post chemical control and pre harvesting. Totally 24 species were collected and identified from 195 sampling points. At the beginning of the growth season Fumaria vaillantti and Polygonum aviculare were dominant species but gradually perennials such as Convovulus arvensis and Circium arvensis dominated. Meanwhile, the importance of some dominant annual species of the early season such as Fumaria vaillantti were reduced. In order to describe the spatial distribution of weeds within the farm, the species variogram in each stage was calculated. Variogram parameters were differed from each other due to the diversity of species and the stages of sampling. The minimum and maximum of nugget effect for current species in first and second stages of sampling was 0.6 and 1.001, respectively. The range of weeds in the field varied between 3.6 – 93.48m. The variogram parameters were used in Kriging and weed's spatial distribution maps were drawn. Generally it could be conclude that the type of crops in rotation and cultural operation affects dynamics of the weeds. On the other hand, the maps showed the patch distribution, lead us toward using site specific weed management.

For increasing the effectiveness of weed management and more understanding of weed population dynamics, spatial distribution needs to more attentions. Infestation levels and spatial distributions of Amaranthus blitoides, Chenopodium album and Solanum nigrum were studied in four 10x30 m corn fields. N-fertilizer was applied in two method of whole application at the time of corn planting (T1 and T2) and equal split application at the time of corn planting and at six-leaf stage (T3 and T4). One of either fields with the same method of N-fertilizer application, received herbicide too (T1 and T3). Weeds Samples were taken four times at the intersection of 2.5m square grids with 23days interval. The first sample was taken June 24, before top-dressing and herbicide application in related plots. For studying weed spatial distribution, the parameters of appropriate semivariogram model were calculated and weed contour maps were constructed by using kriging. The weed semivariograms fitted spherical and exponential models, over four sampling times and fields and spatial autocorrelation during growing season, was moderate to strong. In early growing season, Amaranthus blitoides was the dominant weed species in all fields, but lower density was recorded for Chenopodium album and Solanum nigrum. At the first sampling time, mean density of A. blitoides and S. nigrum in fields with split application of N-fertilizer was respectively more- and less than fields with whole application of N-fertilizer. In the case of C. album an evident difference wasn’t observed. Herbicide application in related plots considerably reduced the density of three mentioned species; however density never became zero. In the majority of cases the lack of herbicide application causes to increase in population density at the second sampling time. Spatial structure was observed in all three species and study on contour maps confirmed the existence of patches that the density was high in their center, but decreasing gradually toward edges. In general, despite of some displacement, structure and location of patches were kept and possibly these places were the locations for weed emergence in next year. So site-specific herbicide application and exploitation of its advantages may be possible; however, more researches are necessary.