جستجوی مقالات مرتبط با کلیدواژه « seed bank » در نشریات گروه « زراعت »

The different species of Amaranthus species are among the most important damaging weeds in the world. Due to the importance of studying the effect of management factors on seed dynamics of different weed species, this experiment aimed to investigate the effect of burial depth and high temperatures on the seed dynamic of different species of Amaranthus in Golestan province including white pigweed (A. albus), prostrate pigweed (A. belitoides), hybrid Amaranthus (A. chlorostachys), redroot pigweed (A. retrofelexus) and green Amaranthus (A. viridis) were performed.

This research was conducted on five amaranthus species of white pigweed, prostrate pigweed, hybrid Amaranthus, redroot pigweed, and green Amaranthus at the seed laboratory and greenhouse of Gorgan University of Agricultural Sciences and Natural Resources. In the first experiment, seed emergence of different species of Amaranthus was studied in eight burial depths including 0, 1, 2, 3, 4, 5, 7, and 10 cm. In the second experiment, seeds were exposed to 50, 60, 70, 80, 90, 100, and 110 °C temperatures for 5, 10, and 15 minutes

All seeds of A. blitoides and A. viridis germinated in the topsoil (zero depth); But, in A. albus, A. retroflexus, A. chlorostachys, 93%, 83%, and 3% of the seeds were emergence at the soil surface, respectively. By increasing the burial depth to one centimeter, the percentage of seeds emergence in different species of Amaranthus decreased significantly and was negligible at ≥ 2 cm depth. Germination test performed on retrieved seeds showed that zero to 16% of the seeds were able to germinate in petri dish, and most of the non-germinated seeds were viable. In all species except for A. chlorostachys high temperatures reduced the germination percentage.

Due to the reduction of seed germination percentage of different species of Amaranthus from a depth of more than one centimeter of soil, it seems that the use of conservation and conventional tillage methods has a good potential to reduce infestation of fields by these weeds. Also, although high temperatures reduce weed infestation in fields, they do not have a significant effect on depleting the seed bank of these species.

Highlights:

1- Seed dynamics of different species of Amaranthus were affected by burial depth and high temperature
2- Deep burial of seeds of different species of Amaranthus causes the stability of their seeds in the soil seed bank.

Weed seed bank in the soil is an essential source of weeds that enables them to be present in the fields. The seed bank density in a crop may reach a million seeds per square meter. Depending on the crop operation, crop rotation, and herbicide selection, the weed seed bank differs according to the location and time. Due to the economic benefits and improved crop ability, plant remains have become an attractive and acceptable way in agriculture. Allelopathic plant remnants can have a beneficial effect on weed control. The allelopathy of these plants plays a vital role in controlling the seed bank of weed soils. Therefore, this study was conducted to investigate the effect of mixing different amounts of residues of three medicinal herbs on the potential of the weed seed bank in the Malekan region.

This study was carried out at Malakan Azad University labs in 2018. Treatments included mixing different amounts of residues (0, 50, 100, and 150 g / m2), and three medicinal plants were cumin, seaweed, and marjoram. Samples had taken from a depth of 0 to 20 cm in an ocher system (7 cm radius) to measure the soil's seed bank. Weeds were isolated, and their species were identified. Laboratory studies were conducted to determine the germination strength of these seeds. This part of the experiment was carried out with three replications in a completely randomized design.

In total, 53915 weed seeds were detected per square meter. The highest seeds in the soil belonging to weed carnivorous and lambspeed were 33254 and 12457 seed per square meter of soil, respectively. The seeds of these two weeds included 95.4% of the seed bank of soil weeds. In this study, the remnants of seaweed and marigold caused a significant decrease in germination characteristics and the growth of seedlings of these weeds. Remains of cumin have little effect on the traits studied. Seed germination and seedlings growth of these weeds decreased by 44.7% and 84.9%, respectively.

By increasing the amount of application of the remains, a more significant reduction in germination and weed growth was achieved. The remnants of the two herbs had a similar effect on germination and seedling growth. Overall, this study showed that the remnants of medicinal plants could reduce the diversity and abundance of seed banks of soil weeds.

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.

This study aims at investigating the effect of herd trampling on soil in Darrehshar town pasture in a complete random survey.Regarding to this study the amountcof germination of soil seed bank wil be investigated.Treatment of the study involves trampled soil by herd, and the soil without herds’ trace on repeated three times.In order to compare the means (averages), . The indices of Simpson and Shannon-Wiener and richness indices were studied and Menhing.The obtained results of the research indicated that grazing livestock stomping had a direct effect on the germination of borried seeds in seed bank soil in both 0-5 cm and 5-10 cm soil depth, so that stamping of Livestock on the amount of indexes of species diversity and richness in the soil free from livestoch sings and effects was more them livestoch stamping. The results of variance analysis showed that there is a significant difference between the values of Margalof enrichmentindices and Manhing, and also between Shanoun- winner variety indices and Simpson ( P .(05>The value of Margalof enrichmentindices and Manhing was 29/6 and 8/62, respectively. And the value of Shanoun- winner variety indices and Simpson was 51/66 and 25/27, respectively, showed that in the soil without herds’ trace on was greater than trampled soil. Understanding these changes can be an appropriate guideline in interpretation of plantcoverchanges and how to manage it in future.

Secondary seed dormancy is announced as the major reason for seed persistence of canola (Brassica napus L). Volunteer’s rapeseeds emerging from the soil seed bank can lead to unwanted gene dispersal to other plants after breaking secondary seed dormancy. In this study, with using poly ethylene glycol 6000, secondary dormancy was induced in 41 lines and 5 cultivars of canola under laboratory condition during 14 days and secondary seed dormancy recorded. This study was conducted in a randomized complete design. High germination percentage was shown in all lines and cultivars (higher than 94 percent), although categorized on five group included very low, low, medium, high and very high after secondary dormancy with using cluster analysis. Among different lines, five and two genotypes were placed in very low and very high groups, respectively. Most of lines were placed in average and low groups. It was observed that 5 varieties (RGS003, Zarfam, Hyola401, Hyola308 and Hyola50) had average secondary dormancy (40-60 percentage) that was related to breeding ignorance about secondary dormancy during seed production process. Lines classification based on different levels of secondary dormancy helps seed producers to select lines with low levels of it along with seed yield and other characteristics in order to deal with problems in seed producing process.

To evaluate the effect of hunting after the release of seed in wheat field a factorialexperiment was conducted as a randomized complete block design with three replications at Karaj during 2012-13. Factors were included plant species at two levels (wild mustard and wild barley), sampling dates at 14 levels (from December, 12 to June, 22 per two weeks) and sampling location at two levels (periphery and center of field). The seeds were transferred to petri and then placed in plots. At each sampling date, a control seed petri were placed at field and then the lost seeds have been measured. The results showed the highest seed hunting in center of field on 4 Khordad was pertained to wild barley and the lowest seed hunting in periphery on 24 Farvardin was belong to wild mustard. The highest number of predators on 18 Khordad was pertained to wild barley, whereas the lowest number of predators on 20 Day was obtained by both weeds and on 4 Bahman by wild mustard. The highest number of predator on 4 Khordad was in the center of field and the lowest number of predators on 20 Day and 4 Bahman was in the center of field and on 20 Day and 28 Bahman in the periphery of field. Ants (Formicidae) and crickets (Gryllidae) had the highest and lowest number of predators, respectively.

Winter weeds have different emergence flashes in field and response to this question whether there is flash emergence after applying herbicide, can be effective in the selection of right time for weed control. Therefore, emergence pattern of the wild oat seedlings was studied for three years from 2011 to 2014 in cereal fields of Fars province. The cumulative emergence pattern of wild oat during 2011-2012 showed that 50% of emergence occurred at growing degree days (GDD) of 115. The emergence percent revealed that 21.09, 45.00, 19.37 and 2.43% seeds respectively at GDD of 99.25, 136.75, 180 and 220 were emergence. The emergence pattern in 2012-2013 crop years also showed that a GDD of 127 was required for 50% emergence. This amount for 2013-2014 crop years was 146 GDD. With regard to the contamination and presence of wild oats in the fields, final results of this study showed that the hypothesis of various flashes after the herbicide application is rejected. All the weed seedlings emerge in in fields during the first month after planting.

The aim of this study was to investigate and to quantify the effect of burial depth on seedling emergence of volunteer canola and wild mustard. Seeds were buried in 12 different depths (1، 2، 3، 4، 5، 6، 8، 10، 12، 15، 20، 30 cm) in 4 replications and seedling emergence was measured daily. Results indicated that emergence percentage of volunteer canola was around 98 % from 1 to 2. 9 cm of burial depth and deeper depths decreased emergence percentage with a slope of -0. 4 and reached to zero in burial depth of 10 cm. Seedling emergence percentage of wild mustard was described using an exponential model on the response to burial depth. According to the model، wild mustard seedling emergence decreased from 66 % in 1 cm depth to 0 % in 8 cm depth. Increasing burial depth leads to reduction of seedling emergence rate that it well quantified for both species. Seeds of these two species that buried in deeper soil layers from 10 cm for volunteer canola and 8 cm for wild mustard can expand soil seed bank and will not emerge. The results of this study may provide useful information in ecological weed management and prediction seedling emergence of weeds.

In this research, seed germination modeling of volunteer canola was conducted satisfactory. Segmented function was used to describe seed germination rate to temperature. Base temperature was 2.73 oC and it was increased with decreasing water potential to about 6.7 oC at -0.8 MPa. The R2 values were 0.94 at sub-optimal temperatures, and this value for supra-optimal temperatures was 0.96. The R2 values showed a good fitness of the hydrothermal time model under both sub- and supra-optimal temperatures. The hydrothermal values were 36.2 and 42.9 MPa oC for sub- and supra-optimal temperatures, respectively. The parameters and relationships estimated here can be used in soil seed bank dynamics models or can be used to establish a new model for the environment. The results of this study will also be useful for future studies of wild mustard biology and ecology.

To investigate the effect of different planting date of cover crops on weed seed bank and population dynamic in corn a field experiment based on randomized complete blocks design with three replications was conducted in Sari Agricultural Sciences and Natural Resources University during growth season of 2010. Treatments consisted of three cover crops, soybean, fenugreek and cowpea in two different planting date (simultaneous with corn and 21 days after planting of corn), along with two control (no weeding and weeding). The results showed that weed seed bank was influenced by cover crops, so that soybean, fenugreek, and cowpea at first and second planting date, and control treatment (no weeding) decreased the numbers of seeds in soils by 49, 52, 26, 27, 49, 51 and 5%, respectively. The results showed that dominant weed populations such as velvetleaf and johnsongrass were also affected by planting date of these cover crops in contrast with control (no weeded). All three cover crops and weeding check increased corn yield significantly as compared with no weeding check. The highest corn yield obtained under weeding check treatment and cowpea cover crop at second planting date. Weed seed bank density at some species was significantly reduced at second sampling stage as compared with first sampling stage.

A field experiment was conducted to investigate the spatial distribution of weeds at the Sari Agricultural Sciences and Natural Resources University in 2011. Field was divided into 42 grids (1. 5×1. 5 feet) then all samples were taken from grids intersection points before corn planting، after harvesting and ear emergence stage. Weed maps and semi variance analysis carried out using RW99 and Gs+ softwares. The results showed that the highest amount of weed population belongs to prostrate pigweed، nutsedge and redroot pigweed، respectively. There was a strong and moderate spatial correlation as spherical and exponential variograms model at all stages of sampling. The seed banks were patches with different sizes and densities. Seed bank patchy pattern at the beginning of season was in accordance with seed bank at the end of season. Knowing the seed bank density، we can forecast weed seedling density during crop growing season.