جستجوی مقالات مرتبط با کلیدواژه "density" در نشریات گروه "زراعت"

Japanese brome (Bromus japonicus Thumb.) is known as the most important grass weed in the wheat fields of Sistan & Baloochestan. Using an additive series design we conducted field experiment over 2008-09 and 2009-10 growing seasons at Zahak, Zabol to characterize interference between wheat and Japanese brome. Wheat densities were considered at five levels of zero, 350, 400, 450, and 500 plants per m2 and Japanese brome at four levels of zero, 100, 200, and 300 plants per m2. Here, we estimated the intraspecies and interspecies competition coefficients, relative competitive ability and niche differentiation. For both years of experiment and in both stages of tillering and physiological maturation of wheat, the intraspecies competition coefficient of wheat ( ) was negative and the interspecies competition coefficient ( ) between wheat and Japanese brome was positive. The relative competitive ability of wheat ( ) showed that each Japanese brome plant was able to have a negative effect on the dry weight of a wheat plant equal to 2.5 wheat plants. The coefficient  showed that the competitive potential of each wheat plant in the tillering stage was 9.5 and 3.3 times more than a Japanese bromus plant in the first and second years of the experiment, respectively. In the interference of wheat and Japanese brome, wheat had a higher competitiveness, especially at the tillering stage. No niche differentiation observed between wheat and Japanese brome and their ecological niche strongly overlapped, which it was more at the tillering stage.

To study the effect of the pre-mix herbicide, clodinafop propargyl+ metribuzin (29% WP), to control weeds of wheat fields an experiment was carried out in a randomized complete block design with 8 treatments and 4 replications in Alborz (Karaj), Fars (Darab), Semnan (Shahroud), and Khorasan Razavi (Mashhad) during 2021-2022. The treatments included the application of the herbicides pre-mixture herbicide Clodinafop propargyl+ Metribuzin ("CloMetri" is used as an abbreviation) at the rates of 500, 600, and 700 g/ha, Metsulfuron methyl+ Sulfosulfuron (Total@, 80% WG) at the rate of 45 g/ha, Mesosulfuron+Iodosulfuron+ Diflufenican (Othello@, 8.25% OD) at the rate of 1.6 l/ha, Clodinafop propargyl (Tapik@, 8% EC)+ Tribenuron methyl (Geranestar@, 75% DF) at the rate of 0.8 l/ha + 20 g/ha, Tapik@ + Bromoxynil+ MCPA (Bromicide MA@, 40% EC) at the rate of 1 + 1.5 l/ha, , and a Weed-free (Hand-weeded) control. The results showed that the application of herbicide treatments significantly reduced weed density and dry weight and increased grain yield of wheat. The Clometri (700 g/ha) showed control efficacy against Veronica persica Poir., Malva neglecta Wallr., Hirschfeldia incana (L.) Lagr.-Foss., Fumaria officinalis L., and Centaurea iberica Trevir. ex Spreng., ranging from 70% to 85%. Overall, compared to the other herbicides in the experiment, the efficacy of clometry herbicide in controlling most weed species was weak and unsatisfactory. Therefore, its use is not recommended as an option for weed control in wheat fields.

Hemp (Cannabis sativa L.) is one of the oldest cultivated annual crops in the world belonging to the cannabaceae family and annual wind-pollinated broadleaf. It is originated in central Asia and considered a multi-purpose crop including stalk fiber (apparel, fabric, bags), stalk hard (animal bedding, mulch, biofuel, filter, and so on), seeds (nut, and snacks), oil (salad oil, cosmetic, shampoo, soap, oil paint, industrial oil, and solvent), leave and inflorescence (anti-microbe (hand soap), and agrochemical products (insecticide and herbicide). Weed competition for nutrients, water, and light led to decreased growth and yield of hemp. Mechanical and agronomical techniques are commonly used for weed management in hemp. Since mechanical and agronomical techniques are expensive and time-consuming, finding a new approach to save time and money is essential. Determination of weed critical period may facilitate arriving at this approach. The critical period of weed control (CPWC) refers to a part of the integrated weed management (IWM) program and is defined as a part of the crop growth cycle in which weeds must be removed for avoiding economic yield losses due to weed competition with crops for water, light, and minerals. On the other hand, CPWC is a period in which crops must be growth-free of weeds. Numerous agents' effects on CPWC include crop species and growth characteristics, crop density, crop variety, and crop planting pattern. The main goal of this study was to determine the effect of hemp density on CPWC and hemp yield and yield components' responses to the critical period of weed control.

A field trial was carried out in 2016 at the research field of Birjand University in South Khorasan Province, Birjand, Iran (latitude 32°, 86′, 49″ N, longitude 59°, 22′, 62″ E, and altitude 1491 m). Before sowing seeds, the field was fertilized with urea (250 kg ha-1) split at two times (sowing time, 2 mount after emergence), P2O5 (100 kg ha-1), and K2O (100 kg ha-1). The field was plowed with a mouldboard plough (30 cm depth), and then harrowing by a disk used for seedbed preparation twice, and finally, leveling the soil surface by leveler tools. Hemp has never been cultivated in this field. The hemp seeds were sown on May 4, 2016, in a cluster, 5 seeds in each hole with 60 cm between rows and 10 and 20 cm between plants in the row for 8 and 16 plants/m2, respectively. Sown depth was 3 to 4 cm. Crop emergence began about 2 weeks after planting. Two weeks after emergence (four weeks after planting), the plants were thinned to reach a determined density. The experiment was arranged in a randomized complete block design (RCBD) in a factorial arrangement with three replications. Each experimental plot was 6 m long, 3 m in width, and included 5 rows. Data were collected in three central rows. Treatments included six weed-infested periods (2 (WI2), 4 (WI4), 6 (WI6), 8 (WI8), and 10 (WI10) weeks after crop emergence (WAE)), in which weeds were allowed to grow to 2, 4, 6, 8, and 10 weeks after that control conducted by hand hoeing until harvest time. In weed-infested control (WIC), weeds were allowed to grow in all growing seasons duration. Six weed-free periods (2 (WF2), 4 (WF4), 6 (WF6), 8 (WF8), and 10 (WF10) weeks after crop emergence (WAE)), which weeds were hand hoeing control to 2, 4, 6, 8, and 10 WAE and then weeds were allowed to grow until harvest time. In weed-free control (WFC), weeds control in all season growth duration. The experimental treatments during the growing season of hemp are described in Figure 1. Seed hemp yield and yield components were determined at the end of the growing season.

Weed-infested and weed-free periods treatments have significant effects on the seed yield and yield components including flower number and seed number per plant of hemp (Table 1). Moreover, hemp density has a significant effect on the seed yield and yield components including flower number and seed number per plant of hemp (Table 1). Higher crop density led to limited CPWC since under weed-infested fields using higher crop density led to improved crop competition ability (Zimdal, 1993). (Hayat et al.,2003) reported that high crop density led to decreased seed yield of crops by increasing inter-species competition. (Purcell et al.,2002) demonstrated the seed yield of soybean depends on crop density whereas by increasing crop density firstly seed yield was increased but under high crop density seed yield was decreased. Therefore, using proper crop density is known as an important challenge to crop production. Flowers per plant, seed number per plant, and seed yield were affected by crop density. Results of this study demonstrated that under weed-infested fields using 16 plants/m-2 is more suitable than 8 plants/m-2 compared to weed-free in Birjand conditions (Dry climate)(Table 2).

A greater understanding of weed behavior can help with IWM strategies. The critical period of weed control determination is a key factor for IWM strategies that led to less introduction of herbicides into the environment, saving money and time, and so on. Data obtained from the results of this study revealed that more crop density led to a decrease in the duration of the critical period of weed control in hemp.

In order to investigate the changes in weed flora in the irrigated wheat fields of Isfahan county over a 15-year period (from 2019 to 2004), a systematic sampling of weeds was conducted in 100 farms with W pattern during wheat tillering to stem elongation stages. In 2004, the dominant weed species was winter wild oat (Avena ludoviciana) with a abundance index of 76.1; however, in 2019 three weed species, including winter wild oat, wild barley (Hordeum spontaneum), and littleseed canarygrass (Phalaris minor) were recognized as the dominant species with abundance indices of 70.1, 42.3, and 28.6, respectively. In 2004, the dominant broadleaf weed species were lambsquarters (Chenopodium album) with a dominance index of 67.9 and prostrate knotweed (Polygonum aviculare) with a dominance index of 31.96. However, in 2019, the highest dominance indices were observed in lambsquarters, prostrate knotweed, and Flixweed (Descurainia Sophia) with abundance indices of 78.4, 38.5, and 39.04, respectively. The correlation between weed distribution and soil factors (nitrogen, phosphorus, potassium, soil texture, and electrical conductivity), crop rotation, and herbicides was examined using canonical correspondence analysis (CCA). Littleseed canarygrass, wild barley, field brome (Bromus commutatus), licorice (Glycyrrhiza glabra), hoary cress (Cardaria draba), and yellow sweet clover (Melilotus officinalis) showed the highest correlation with soil nitrogen levels.

In order to evaluate yield and yield components in intercropping barley with vetch, a two-year field experiment was conducted at the Agricultural and Natural Resources Research Station of Miandoab. The arrangement consisted of 9 mixing treatments with densities of 200 Vetch plant + 300 Barley plant, 200 Vetch plant + 500 Barley plant, 200 Vetch plant + 700 Barley plant, 400 Vetch plant + 300 Barley plant, 400 Vetch plant + 500 Barley plant, 400 Vetch plant + 700 Barley plant, 600 Vetch plant + 300 Barley plant, 600 Vetch plant + 500 Barley and 600 Vetch plant + 700 Barley plant per square meter and sole culture of both crops. The experimental design was a randomized complete block design with four replications. The result showed The highest spikes per square meter, thousand kernel weight, biological yield, and grain yield in barley were observed in the sole culture of barley. Also, the highest plant height, number of seeds per plant, thousand kernel weight, biological yield, and grain yield in vetch belonged to the sole culture of vetch. However, the highest Land equivalent ratio (LER) belonged to treatments of 200 Vetch plants + 500 Barley plants by 1.49,

Rice (Oryza sativa) is a major cereal crop and staple food for more than half of the world's population. About 90% of the world's rice is produced and consumed in Asia. Iran is one of the arid and semi-arid regions and due to the lack of water in many parts of the country, the area under rice cultivation decreases. Direct rice cultivation is a good way to save water. The most important challenge in this cultivation system is weed control. The traditional methods of weed control in rice include hand-weeding by hoe or hand pulling, but this is becoming less common because of labour scarcity at critical time of weeding and increasing labour costs. Herbicides play a key role in weed control and are used extensively today. Therefore, this experiment was conducted to evaluate the effectiveness of different weed management practices for direct seeded rice at varying row spacing. This study was conducted to investigate the effect of planting distance on rows and herbicides on weed suppression and direct rice cultivation performance in the research farm of Sari Agricultural Sciences and Natural Resources University as a factorial experiment in a randomized complete block design with three replications in 2019. Distance between plants at two levels of 3 and 5 cm and chemical management of weeds in five levels of weed-free (control), weed-infested (control), application of trifamone + ethoxysulfuron herbicide 30% (council active) at the rate of 150 g ha-1 in stage of 2 up to 6 leaves of weeds, application of bisopiribac sodium herbicide OF10% (nomini) at the rate of 250 ml ha-1 in stage of 2 to 6 leaves of weeds and application of a mixture of two herbicides halofop butyl OD 20% with 2.5 liters ha-1 with basagran (bentazone) were 3 liters ha-1 in the 2 to 6 leaves stage of the weeds. Results showed that although planting row spacing had no effect on the desired traits; however, weed management had a significant effect on the studied traits. Visual evaluation of weed damage in two evaluation stages (15 and 30 days after spraying) showed that among the chemical control treatments, trifamone + ethoxysulfuron herbicide was superior to other herbicides with 75 and 83.33% weed control, respectively. The lowest weeds biomass was observed in 6 weeks after spraying (20.50 g m-2) and 10 weeks after spraying (20.83 g m-2) in trifamone + ethoxysulfuron herbicide treatment, which was not significantly different with weed free (control). The highest height of rice plants (103.17 and 98.41 cm) was observed in the complete weed control and trifamone + ethoxy-sulfurone herbicide treatments, respectively. It is worth mentioning that the maximum biological yield of rice (6244.4 and 5808.4 kg ha-1) and grain yield (2391.218 and 2290.27 kg ha-1, respectively) was observed in weed-free (control) and application of triafamone + ethoxysulfuron herbicide. According to the results of this experiment, the use of trifamone + ethoxysulfuron herbicide at the rate of 150 g ha-1 is recommended for proper control of weeds in direct rice cultivation. The highest and lowest height, number of tillers and spike length were observed in weed-free control treatment and weed-infected control treatment. Among the herbicides used in this experiment, in the treatment of triafamone + ethoxysulfuron with better weed control, In plant height, tiller number, spike length and number of seeds per spike were superior to other herbicides. According to the results of the experiment, the application of the herbicide triafamone + ethoxysulfuron, while better control of weeds, can increase grain yield.

In order to study the competitive ability of wheat against weeds as affected by cultivar and nitrogen fertilizer application method, an experiment was conducted under farm condition in 2015-2016. The experiment design was factorial arranged in RCBD with three replications. The treatments were: A factor included wheat cultivars(Atilla, Sirwan, Chamran2, Shiroodi and Atilla weed polluted as control), B factor included nitrogen fertilizer application method included (broadcasting, strip application and split application). Urea fertilizer was used as Nitrogen source. Results showed that the highest weed dry weight (10.74g) obtained from broadcast application of fertilizer and the lowest weed dry weight (5.53g) obtained from split application of fertilizer. The highest dry weight of weeds belonged to Sirwan cultivar and broadcast application of fertilizer and The lowest dry weight of weeds belonged to Chamran 2 and Shiroodi cultivars and split application of fertilizer. competitive ability of Sirwan and Chamran 2 cultivars against weeds , was less than other cultivars and density and dry weight of weeds was more in different stages of sampling. The highest yield belonged to split application method and the lowest yield belonged to broadcasting method of fertilizer application.

In order to study efficacy of prosulfuron+dicamba for control of wheat broadleaf weeds, an experiment was conducted in randomized complete block design with four replications at Zarghan, Dezful, Karaj and Mashhad regions during 2018-2019 cropping season. The treatments were included of bromoxynil+MCPA (1.5 l ha-1 of Bromicide-MA® 40%), bromoxynil + 2,4-D (1.25 l ha-1 Buctril Universal 56%), bazagran+dicloprop ( 2 l ha-1 Basagaran-DP® 6.56%), triasulfuron+dicamba (165 g ha-1 Lintur® 70%), and the new herbicide prosulfuron+dicamba (300, 400 and 500 g ha-1 alone or mixed with adjuvants). The results showed that prosulfuron+dicamba in all doses, alone or mixed with adjuvants, caused a decrease in the dry weight of the dominant weeds in Karaj (75 to 100%), Zarghan (85 to 93%), Dezful (70 to 100%) and Mashhad (42 to 97 percent), but compared to other herbicides, there was no significant difference in saving wheat yield in most areas. Lintur® was the most inefficient (50%-75%) and Buctril Universal® was the most efficient (more than 85%) herbicide in our experiment. The most important weeds include Descuriania sophia, Fumaria vailantii, Galium tricornutum, Centaurea depressa, Carduus sp., Rapistrum rugosum, Veronica persica, Malva neglecta and Sinapis arvensis. As a recommendation, prosulfuron+dicamba can be used in the dose of 300 g ha-1, alone or mixed with adjuvants (0.5% v/v of Cytogate). No visual damages were observed from prosulfuron+dicamba application on wheat.

Plant Protection Organization (PPO) has registered fourteen commercial herbicides formulations for weed control of corn in Iran (Nourbakhsh, 2021). Among these herbicides, eight herbicides contain one active ingredient and the other six have two or three active ingredients including acetolactate synthase (ALS) enzyme inhibiting groups - similar-auxin groups, photosynthetic inhibitors of photosystem II and inhibitors of fatty acids and cell division, which are sometimes formulated with safeners. Weed species do not similarly respond to herbicides and previous studies showed some existing inherent tolerance, causes the percentage control of some of the weed species being lower than the others (Hadizadeh, 2016). Thus, new herbicides with several active ingredients are suggested to be used to suppress such weeds. The aim of this work was to find the best chemical treatments against weeds in corn production based on using new herbicides dicamba+ mesotrione+ nicosulfuron and comparing their efficacy with the common newly or some of older registered herbicides in the major corn growing areas of Iran.

A field study was conducted in four regions of Iran, including Mashhad, Ahwaz, Zarghan and Kermanshah during 2019 growing season. The statistical layout was a completely randomized block design with four replicates. Seven chemical treatments were mesotrione+s-metalachlor+terbuthylazine (Lumax® 537.5SE post-emergence, 4.5 l ha-1), nicosulfuron+rimsulfuron (Ultima® 75%WG, 175 g ha-1), topramezone (Clio® 29.7%SC, 150 ml ha-1), thiencarbazone+isoxaflutol+cyprosulfamide (Adengo® 46.5%Sc, 440 ml ha-1), and the new herbicide dicamba+mesotrione+nicosulfuron with five recommended doses (Calisto Solid 569.5 WG, 400, 500, 600, 700 and 800 g ha-1). A hand-weeded treatment and an unweeded treatment served as controls. Weed density and weed dry weight for each plot were measured four weeks after the last application the herbicides. Corn was harvested from 10 m2 of each plot after removing border plots. Corn grain yield was determined after adjusting the moisture level of grain to 14 %. To measure corn biological yield, samples of 10 corn plants were taken and then were dried in an oven. Data from each region were subjected to statistical analysis using SAS/STAT statistical software and the means were separated by LSD (α=5%).

The results showed a diverse spectrum of weeds (18 species) at the experimental locations. Pigweed species (Amaranthus spp.) were present in all tested locations but were not dominant in Ahwaz. The next dominant weed species were Portulaca oleraceae L. and Chenopodium album L. in Mashhad and Zarghan; Physalis divaricate L. in Ahwaz and Zarghan, Convolvulus arvensis L., Echinochloa crus-galli (L.) P. Beauv., and Corchorus olitorius L. in Ahwaz; Hibiscus trionum L., in Mashhad; Glycyrrhiza glabra L. and Xanthium strumarium L. in Kermanshah and finally Sorghum halepense (L.) Pers., was dominant in Zarghan. Across the experimental locations, dicamba+mesotrione+nicosulfuron was efficient at 700-800 g ha-1 application doses for weed control (75 to 88%). However, when applied at dosage of under 700 gl ha-1, its weed control efficiency was lower (50 to 70%). Topramezone and nicosulfuron+rimsulfuron were inefficient in controlling weeds in all the locations. In contrast, thiencarbazone+isoxaflutol+cyprosulfamide was among the most efficient treatments wich these findings are in agreement with the results of some previous studies (Hadizadeh et al. 2015; Hadizadeh et al., 2020). E. crus-galli was identified as the most difficult-to-control weeds and G. glabra and P. oleraceae were the next ones. None of doses of new herbicide showed injury symptoms on corn.

Dicamba+mesotrione+nicosulfuron (700 and 800 g ha-1) showed 70-85 weed control efficiency averaged in the all experimental locations and it could be recommended to be used in corn field after registration process. Due to environmental concern, it could be applied at lower doses when difficult-to-control weeds were not present. Thiencarbazone+isoxaflutol+cyprosulfamide was found to be the high efficient herbicide. Barnyard grass, licorice and common purslane were difficult-to-control weed species or there were not controlled by new herbicides. We also suggest evaluation of the herbicides for their residual effects on the succeeding crops.

In order to investigate the role of inter-species interference and competitive outcome of barnyard grass (Echinochloa crus-galli) and bulrush (Bolboschoenus planiculmis) weeds with Guilaneh cultivar of rice, a factorial experiment with two factors including weed species (barnyard grass and bulrush) and rice: weed ratios in each pot (0: 4, 1: 3, 2: 2, 3: 1, and 4: 0) was conducted as a randomized complete-block design with three replications. The results showed that, except for height, all other traits of rice decreased more in competition with barnyard grass than competition with bulrush. The percentage of more reductions of traits in rice-barnyard grass competition than rice- bulrush competition, averaged over planting ratios, were 10 and 21% for biological yield, 12 and 23% for seed yield, 10 and 21% for number of panicle, 13 and 25% for number of filled seeds, 7 and 16 for total number of seeds, and 10 and 17% for number of tillers on pot and single plant levels, respectively. These results, along with the replacement series diagrams studies have indicated the severe competition of barnyard grass with rice plants. However, no significant difference in the competitive effect of the two weed species, as well as the insignificant dominance index and the ratio of barnyard grass and bulrush competition, indicates the importance of bulrush as a new weed in rice fields. Therefore, effective management of bulrush in addition to barnyard grass should be taken into consideration in the development of the weed management programs in paddy rice fields.

In order to survey the efficacy of several pre-and post-emergence herbicides on weed control in the autumn cultivation of chickpeas, a split-plot experiment was conducted in a randomized complete block design with four replications in the Sararoud region during 2021–2022. The main plots contain two tillage systems (conventional tillage and no-tillage). The subplots include 12 herbicide treatments (Trifluralin, Trifluralin + Bethanal progress, Isoxaflutole, Isoxaflutole + Bethanal progress, Oxyfluorfen, Oxyfluorfen + Bethanal progress, Imazethapyr, Imazethapyr + Bethanal progress, Fluorochloridone, Fluorochloridone + Bethanal progress, Metribuzin, Metribuzin + Bethanal progress, and two controls (weed-free and weed-infested)). The maximum decline in weed dry weight was observed in tillage + Fluorochloridone, tillage + Isoxaflutole, tillage Oxyfluorfen, and no-tillage + Fluorochloridone at about 51%, 48%, 46%, and 45%, respectively. The greatest decrease in weed density is for tillage + Fluorochloridone and tillage + Oxyfluorfen + bethanal progress, tillage + Metribuzin + bethanal progress, tillage + Fluorochloridone + bethanal and tillage + Imazethapyr were registered with 47, 47, 43 and 40% reduction respectively. Conventional tillage reduced the density and dry weight of weeds, but this reduction was statistically significant for the dry weight of weeds. The highest yield of chickpea seeds in tillage + weeding, weeding, tillage + Trifluralin + bethanal progress, conventional tillage + Oxyfluorfen and no-tillage + Trifluralin + bethanal progress treatments are 846, 664, 528, 502 and 498 kg per hectare, respectively. The most effective herbicides in controlling weeds were Fluorochloridone, Isoxaflutole and Oxyfluorfen, and the highest yield of peas was recorded for Oxyfluorfen.

In order to investigate the effects of reduced row spacing from usual 75 cm to 25 cm (UNR), an experiment has been conducted in two locations: Davarabad agricultural research station (Semnan Province) and Varamin Central Agricultural Research Station. The experimental design is RCBD laid out in split plots with three replications. The main plots are the planting dates (May 22 and Jun 5, 2020) and five cultivars, i.e. Khorshid, Kashmar, Sajedi, Hekmat, and Khordad serve as the sub plots. The results show that location effect on vegetative and reproductive attributes has been significant. UNR boosts the yield in Aradan, but in Varamin region, this planting method, not only has failed to increase the yield, but has reduced it significantly. This is due to reducing the boll number as a result of rank growth of plants in UNR system. Reduction of row spaces from 75 to 25 cm enhances the number of monopodials, sympodials, and plant height. In Varamin, plant height of all cultivars are higher than 119 cm. the highest yield in this region obtained from Khordad as Control (3886 kg seed ha -1). The highest yield in Aradan, obtained from Khorshid (5702.5 kg seed ha -1) in UNR system. This shows that the UNR planting of zero type varieties is more adabtable for Garmsar condition than that of Varamin.

This research was carried in cropping years 2017-18 and 2018-19 to study the effect of plant density on morphological traits, flowering pattern, boll production and seed cotton yield of new cotton cultivars in Varamin region of Iran. In this research, five cotton cultivars including Varamin, Shirpan603, Cocker100, NO200 and SP731 in three plant densities were evaluated using a factorial experiment in a randomized complete block design with three replications. In this study, the number of flowers and flowering date in cultivars for 11 weeks (1 July to 15 September) were counted. The results of analysis of variance showed that the differences between cultivars were significant for plant height, number of nodes, number of flowers, number of bolls and fiber and seed cotton yield at 1% level. The results also showed that there is a significant difference between the years of project implementation for plant height, number of bolls and fiber and seed cotton yield at the level of 1%. The mean of plant height for the first and second years were 93.2 and 119.9 cm and the average number of bolls per plant were 15.9 and 11.41 and the seed cotton yield were 5242 and 4050 kg/ha, respectively. In this study cultivars did not differ significantly in terms of number of days from planting to flowering, number of days from flowering to harvest and early ripening. Investigation of flowering process in 11 weeks showed that the peak of flowering for both years of research was the eleventh week after planting with an average of 41.8 and 44.6 flowers per plant. Most of the bolls were produced from the flowers of the eleventh week for first year and from the flowers of the tenth week for second year. The cumulative growing degree days during the vegetative and reproductive growth period for two years of experiment was significantly different.  So that at the end of the seventeenth week after planting (last week of flowering) the cumulative growing degree days in the first and second years was 1734.9 and 1245.5, respectively, Which can be one of the important reasons in reducing the number of bolls and fiber and seed cotton yield in the second year.

In order to investigate the effect of seed amount consumption on the yield of dryland wheat cultivars, an experiment was conducted based on completely randomized block design in 3 replications in a private farm in Hesar Valiasr (AJ) village of Avaj city in the crop year of 1402-1401. The experimental factors included the amount of seed at the levels: 90, 120 and 150 kg/ha cultivars in 3 levels: Azar-2, Hashtroud and Sadra. To investigate the agricultural traits at harvesting time, eight plants were randomly selected from each plot. The results of the study showed that the amount of seed consumption had a significant effect on the traits, number of spikes per plant, number of seeds in the main spike, number of seeds in secondary spike, number of seeds per plant and 1000 grains weight. The mean comparison of simple effects show that the highest seed yield, harvest index was related to Azar 2 variety and the highest biological yield was related to Azar 2 and Hashtroud varieties. In the seed consumption rate treatments, the highest biological yield was gained in 150 kg/ha of seeds consumption, and the highest seed yield and harvest index was related to 120 kg/ha of seeds consumption. The mean comparison interaction effect of seed rate and variety demonstrated that application of 120 kg/ha in Azar-2 variety had the highest seed yield (1226 kg /ha) compared to 90 kg/ha seed application in Sadra variety (839.3 Kg/ha) as the lowest seed yield, (31.56% increase between 2 treatments). In all evaluated traits, Azar 2 showed superiority over other cultivars.

By identifying the weed seed bank can be ascertained to the composition and density of weed seed bank species and flora during the growing season and in choosing the best time and method for effective control of weed seeds in the soil was careful. Since continuous cultivation of a plant in the farm increased the seed bank of weeds, therefore, in order to describe the plant communities of the farm surface and evaluate any changes in them, it is necessary to know and study the soil seed bank. In fact, knowing the seed bank can help control future weeds on the farm and focus on better management operations. This study was conducted in order to evaluate the effect of onion monoculture continuing on weed density and diversity in the conventional agroecosystems of Jiroft region.

Weed seed bank sampling was performed from two soil depths of 0-20 and 20-40 cm by systematic random method. Density and diversity of weed seed bank were determined by germination method in greenhouse conditions. The study population were includes soil samples from four onion monoculture crops with a duration of less than three years (S1), between three to five years (S2), between five to eight years (S3) and more than eight years (S4) and long period fallow system (F). Analysis of variance of data related to different indices and comparison of different indices of diversity and richness in different onion monoculture systems were calculated by Duncan test.

At both 0-20 and 20-40 cm depths, the highest density was related to chameleon weeds. The total number of germinated seeds in greenhouse conditions in fallow and onion monoculture systems at depths of 0 to 20 was about 4140 seeds in m3 of soil that at this depth, F and S4 cropping systems had the lowest and highest number of weeds with an average of 221 and 1704 seeds in m3, respectively, and the majority of seeds were observed at this depth. At a depth of 20-40 cm, 2049 seeds in m3 of soil were observed. At this depth, S4 and F cropping systems with the average of 830 and 143 seeds had the highest and lowest number of weeds, respectively. Also, the results showed that continuous onion monoculture at both depths had a significant effect on weed diversity and species richness indices and S4 and F cropping systems had the highest and lowest diversity and richness, respectively. In fact, weed density increased with increasing continuous onion monoculture.

Because the density of weed seeds in fields under continuous cultivation is higher than fallow and a higher proportion of seeds accumulate in the surface layer of the soil. So, seed density can be reduced in the seed bank with proper rotation. Therefore, it is recommended to use crop rotations with a diverse collection of winter and spring plants instead of continuous cultivation of a crop that by increasing diversity, it provides suitable conditions for better control and interruption of weed life cycle.

All over the world, there are high salinity lands and most of those considered as an arid or useless lands (from agriculture aspect) for lack of knowledge about resistant varieties. Quinoa plant indicate significant resistance to wide range of Abiotic stress such as salinity and cold. Also this plant is protein-rich and can be a good alternative to rice and wheat. It is necessary to study about this kind of plants in the critical condition (saline soil & dry farming) more than ever. In this paper we investigate about the impact of date of planting and density in dry farming and saline soil on quinoa plant yield.

In this study, the experiment, split plot design in completely randomized block base format with three repetition in the crop year 2019 (1397- 98) was performed in one of the farms of Gomishan city, Golestan province. Main factor consists of three planting date (February 4, March 6, April 4) and subsidiary factor has three density (60, 80, 100 and 120 plants per m^2). To determine the length of growth stages and dry weight and doing analysis, Sampling was done once in every two weeks. Final yield is determined by split middle line. during the growth season the important dates of plant phenology such as time for emergence & seedling development, physiological maturity, flowering and grain development divided by different treatment notes were taken. lastly, data obtained were analyzed by statistical software SAS and average data evaluated by LSD test.

The results indicate significant impact of planting date on plant height, number of seeds per panicle, dry weight of the plant and weight of one thousand seeds significance 1 percent level and weight of panicle, number of seeds of branch were at significance 5 percent level. Maximum values of this functional traits was obtained in planting date february 4. and planting date March 6 has the lowest values of these traits. plant height, number of seeds per panicle, wet and dry weight of the plant significantly affected by density factor. all interactions of both factor had huge impact on measured traits. most yields in 60 and 80 density plants per m^2 were significantly more than this trait's value in other planting density. results of this study indicate that february 4 was the best quinoa planting date (in comparison to other reviewed planting dates) for Gomishan and its condition, also 80 density plants per m^2 (high density without any decreased yield) is the most suitable for there.

Due to the quinoa high resistance to drought and salt stress as well as appropriate performance, as a strategic product could be recommended to farmers. by the results of this paper we can conclude that february 4 is the best planting date for saline soil and dry farming. delay to cultivation has a significant decrease in reviewed traits. moreover, because 80 density plants per m^2 increased the plant yield in most traits, then it could be considered as a most appropriate density to this study condition. however to confirm this findings it is necessary to check this experiment another year.

In order to investigate the effect of seed decay, plant density and defoliation on morphological, yield and yield components of bread cultivar, an experiment in the cropping years 2016-17 and 2017-2017, in Galikesh city of Golestan province with a longitude of 26 degrees and 55 minutes, Latitude 16 degrees and 37 minutes and altitude 200 meters above sea level. The experiment was a factorial randomized complete block design with three replications. Experimental treatments included two levels of seed decay including decayed (control) and decayed seeds (72 hours at 45 ° C), three density levels including 350, 400 and 450 seeds per m2 and decolonization at four levels including removal of all leaves, removal of all Leaves except flag leaf and delete all leaves except flag leaf and before, without leaf removal (control). The simple effects of accelerated leaf removal and accelerated aging and wheat seed density on yield and its components were significant at the level of one percent. The results showed that seed degradation significantly reduced biological yield, 1000-seed weight, number of spikes per square meter, 1000-seed weight, grain yield and harvest index. The highest biological yield, 1000-seed weight, number of spikes per square meter, number of seeds per spike, 1000-seed weight, grain yield and harvest index were obtained at a density of 450 seeds per square meter, which can be expressed as the desired density for this cultivar. Decolorization significantly reduced biological yield, number of spikes per square meter, number of seeds per spike, grain yield, biological yield and harvest index.

In order to investigate the effect of planting pattern and nitrogen and megafol on grain yield, yield components, and seed protein of chickpea (Cicer arietinum L.) under rainfed conditions, a factorial experiment has been conducted in a randomized complete block design with three replications in Gonbad Kavous University farm during growth season of 2017-2018. The planting pattern is in three levels of 30×11, 45×7.4, and 60×5.5 cm (30 plants. m-2) and the factor of use of fertilizers in five levels of non-consumption and consumption of 50 and 100 kg nitrogen and one and two liters of megafol per hectare. The results show that the highest seed yield is related to 30×11 and 45×7.4 and the lowest is related to 60×5.5 cm. Seed per plant and seed yield in application of 100 and 50 kg N ha-1 has been higher than others. The highest and the lowest protein percentage of seeds is related to 60×5.5 and 30×11 cm. 1000-seed weight in application of 100 and 50 kg N ha-1 and 2 liters of megafol has been more than other treatments. The harvest index in application of fertilizer is the maximum and in treatment of non-application of fertilizer is the minimum. In addition, because of more effect of nitrogen on seed yield compared to megafol and non-significant differences between consumption of 100 and 50 kg N ha-1, it seems that consumption of 50 kg N ha-1 and planting pattern of 30×11 is the most appropriate advice for planting of rainfed chickpea in Gonbad Kavous condition.

Weed infestation in arable lands is much more than one species. Thus, it is important to pay attention to the interaction of multy species of weeds. To study the effect of redroot pigweed (Amaranthus retroflexus L.) and barnyardgrass (Echinochloa crus-galli (L.) P. Beauv) interference on yield and essential oil of fennel (Foeniculum vulgare Mill.), an experiment has been done in Research field of Sari Agricultural Sciences and Natural Resources University during 2017. It has been arranged in a factorial arrangement based on randomized complete block design with three replications with the experimental factors being three densities of redroot pigweed (0, 4, and 8 plants m-2) and three densities of barnyardgrass (0, 4, and 8 plants m-2). The highest grain yield (2230 kg ha-1) and essential oil content (2 %) are obtained at weed free plots. The density of 8 redroot pigweed plants m-2 at simultaneous interference with 0, 4, and 8 barnyard grass m-2 reduce grain yield by 30.1%, 62.9%, and 75.7%, and essential oil content by 24.5%, 26.2%, and 29.5%, respectively, compared with weed free plots. The coefficient of redroot pigweed competitivity is predicted to be higher than barnyardgrass, and the interference of 14.5 barnyardgrass plants m-2 or 7.7 redroot pigweed plants m-2 decreases fennel grain yield by 50%.

Among oilseeds, sesame (Sesamum indicum L.) is known as the queen of oilseeds due to its significant amount of antioxidant compounds, essential amino acids and unsaturated fatty acids. Among the necessary managements to achieve maximum crop production, the selection of cultivar, density and planting pattern could be mentioned. Different sesame cultivars have various growth characteristics (for example, branching) and each of them is suitable for a planting method with a certain density. The aim of this study was to evaluate the planting pattern and suitable density for two sesame cultivars.

In this study, the effect of planting pattern (single or double row(s) on ridges), plant density (20, 30 and 40 plants m-2) and sesame cultivars (Oltan and Naz Tak Shakheh) based on factorial experiment in a randomized complete blocks design were evaluated in three replications during 2019 and 2020 in Karaj region. Plant height, grain yield and yield components, dry matter yield, harvest index and oil percentage and yield were evaluated. Statistical analyzes were performed using SAS software and LSD test was used to compare the main means and slicing was used to compare the means of interactions.

Analysis of variance showed that effect of planting pattern factor on plant height and dry matter yield, plant density factor on all traits (except 1000-seed weight) and cultivar factor on all traits (except harvest index) were significant. Comparison of means showed that the mean of plant height in planting pattern of double rows on ridges (126 cm) was significantly higher. Among the yield components, the number of capsules per plant at densities of 30 and 40 plants m-2 (57 and 60, respectively) were the highest, which were statistically significant compared to the density of 20 plants m-2 (50). The number of seeds per capsule at the density of 20 plants m-2 was the highest (58) which showed a statistically significant difference compared to the other two densities. Among the studied densities, the highest grain yield (993 kg ha-1) was obtained from the density of 40 plants m-2 and the lowest grain yield (798 kg ha-2) was obtained from the density of 20 plants m-2. Among the two studied cultivars, Oltan cultivar had the highest yield and grain yield components which showed a statistically significant difference compared to Naz Tak Shakheh. The highest oil yield was produced by Oltan cultivar in each of the densities of 30 and 40 plants m-2, which statistically did not show a significant difference in planting pattern of single or double row(s) on ridges.

This study showed that Oltan cultivar is recommended in planting pattern of single row on ridges and in density of 30 plants m-2 for Karaj region.