حمید رحیمیان مشهدی

Swallow-wort (Cynanchum acutum L.) is a perennial and invasive weed that infested many sugarcane fields in Khuzestan. Field experiment was conducted to find out an efficient method for C. acutum control in sugarcane during 2018 and 2019. The experiment was split-split plots in a randomized complete block design with three replications. Main plots were pre-emergence application of metribuzin, metazachlor + qinmerac, pendimethalin, indaziflam and acetochlor; Sub plots were one time hand hoeing (four weeks after pre-emergence application), two-times hand hoeing (four and eight weeks after pre-emergence application), and without hand hoeing and sub-sub plots were post emergence application of 2,4-D+MCPA, mixture of 2,4-D+MCPA and metribuzin, and bromoxynil + MCPA herbicides. Results showed that individual application of Pendimethalin, and indaziflam herbicides, two-times if hand hoeing, and then post emergence application of 2,4-D+MCPA and metribuzin as a had the highest efficiency with an average of 96% in reducing mass dry weight. The application of mentioned treatments increased cane yield 104.7 and 102.9 t/ha respectively compared to the control (without weeding, with 110 t. ha-1). However, the experimental treatments did not show a significant effect on quality traits of sugarcane.

Quinoa is a pseudo cereal from Amaranthaceae family, which is currently considered as a suitable alternative for plants with high water consumption due to its high nutritional value and stresses tolerance, especially drought and salinity. Meanwhile, reduction in crop yield caused by weeds competing for water, light and nutrients is well known. Hence, a study was conducted in Karaj to investigate the competitive capacity of quinoa with weeds under normal irrigation and drought stress and also to determine the required time for weed control. The experiment was arranged in split plot randomized complete block design with four replications consisted of irrigation levels (60, 80 and 100 mm evaporation from the evaporation pan) as main plots and weed control levels (0, 7, 14, 28 days of control and control in all seasons) as subplots. The highest quinoa grain (331 g/m2) and biological yields (1262 g/m2) were obtained under normal irrigation in weeds free treatment. Also, the lowest grain and biological yields were 139 and 723 g/m2, respectively that obtained under high drought stress in weeds infestation during growing season. In one month weeds free treatment under medium drought stress, grain and biological yields were 290 and 1010.25 g/m2, which show that despite the competitive potency of summer weeds, quinoa has good competitiveness in drought stress, and with one month of weed control, can achieve performance close to full control. In logistic model fitting to the grain yield, the maximum and minimum values of y0 and a, i.e. upper and lower limits, were observed in normal irrigation and high drought stress, respectively; although, the maximum and minimum values of GDD50 were obtained in high drought stress and normal irrigation, respectively.

To investigate the effrct of various densities of wild oat, application time and type of herbicide on wild oat control and yield and yield components of wheat, a split spilt plot experiment was carried out base on randomized complete block design (RCBD) with 3 replications in a field in Fars Province )Marvdasht city) in the cropping year of 2014-2015. The different densities of wild oat (0, 20, 40, 80, 160 and 320 plants m2) as the main plot, two herbicides including mesosulfuron + iodosulfuron + mefenpyr-diethyl (Atlantis18 g a.i. /ha) and clodinafop-propargyl (Topik, 64 g a.i. /ha) as sub-plot and application time (18 (8 leaves) and 23 Zadoks (tillering) stages) as sub-sub plot were considered. According to logistic model (parameter Den50), 127 and 95 wild oats per m2 was required to reach a 50% reduction in dry weight of wild oat in clodinafop-propargyl herbicide treatment at 8 and 23 Zadoks stages, respectively, whereas, for 50% reduction in dry weight of wild oat in mesosulfuron + iodosulfuron herbicide treatment were 141 and 149 wild oats/m2, respectively. The regrowth of wild oat in clodinafop-propargyl compared to mesosulfuron + iodosulfuron herbicides was higher in tillering compared to 8 leaves in all densities. Hyperbolic model for grain yield showed that in Topik herbicide treatment at both application times, 50% reduction in the yield was observed in 118 and 83 wild oats/m2 and in mesosulfuron + iodosulfuron herbicide treatment at both application times, 50% reduction in the yield was observed in 423 and 221 wild oats/m2.At higher wild oat densities, of mesosulfuron + iodosulfuron application is recommended at 18 Zadoks stage.

A factorial experiment based on randomized complete block design (RCBD) with three replications in two fields in Marvdasht city (Fars province, Iran) was conducted to evaluate the effect of different herbicides at different times based on growing degree day (GDD) Avena spp. controlling. The first factor was five selective wheat herbicides including clodinafop-propargyl (Topik 64 g a.i./ha), fenoxaprop-p-ethyl (Pumasuper, 75 g a.i./ha), mesosulfuron + iodosulfuron + safener mefenpyr-diethyl (Atlantis, 18 g a.i./ha), sulfosulfuron (Apirus, 20 g a.i./ha), and metsulfuron methyl + sulfosulfuron (Total, 30 g a.i./ha). The second factor was application time of herbicide at 19 (398 GDD), 23 (435 GDD), 29 (502 GDD) and 31 (618 GDD) zadoks stages. Increasing GDD (from 398 to 618 GDD) increased regrowth percentage and dry weight of Avena spp. The maximum   regrowth percentage and dry weight of Avena spp were observed in clodinafop-propargyl, fenoxaprop-p-ethyl and sulfosulfuron herbicides treatments while they were applied at the 618 GDD (Zadoks 31). The minimum regrowth percentage (26%) was obtained in mesosulfuron + iodosulfuron herbicide treatment at the 398 GDD (Zadoks 19). The highest grain yield (>5664 Kg/ha) was obtained using metsulfuron methyl + sulfosulfuron and mesosulfuron + iodosulfuron at the 435 GDD. The mesosulfuron + iodosulfuron (Atlantis) herbicides treatment controlled Avena spp appropriately at the 398 GDD, however it led to wheat leaf burning due to the dry conditions, so that a 50%  yield reduction (2679 Kg/ha) occurred in comparison to the 435 GDD. It is recommended that the early application of metsulfuron methyl + sulfosulfuron and mesosulfuron + iodosulfuron (435 GDD) with regard to weather conditions may reduce the wheat grain yield loss and Avena spp regrowth.

To evaluate the different doses of mesosulfuron + iodosulfuron (Atlantis) and application time on two Kurdistan and Fars populations in crop year 2013-2014, a split spilt plot experiment was carried out in the field in Fars province. The different doses of herbicide (0, 6, 12, 18, 24 g ai/ha) as the main plot, two populations of wild oat (Kurdistan and Fars respectively) as sub-plot and application time at stages of 18 (8 leaves) and 23 zadoks (tillering) as sub-sub plot were considered. The regrowth percentage of wild oat Fars and Kurdistan populations in highest dose (24 g ai/ha) at two herbicide application times in 8 leaves (16.16 and 4.5%) and tillernig (23 and 6%) were obtained respectively. It is remarkable that the regrowth percentage of wild oat at reduced dosage (12 g ai/ha) at tillernig time was more than 8 leaves in two Kurdistan and Fars populations. Dose-response equations for dry weight of wild oat showed that the required level of dose for reaching a 50% decrease in two populations of wild oat and application times was different. Doses of 7.93 and 8.38 g ai/ha in order to achieve a 50% decrease in the dry weight of Kurdistan population in two application times of 8 leaves and tillering was required. These amounts for a 50% reduction in dry weight of Fars were 9.89 and 9.66 g ai/ha, respectively. In reduced doses of herbicide with delayed application time, regrowth and dry weight of wild oat increase and effect on grain yield and number of spike in wheat. The application of reduced doses (12 g ai/ha) is recommended at stages of 18 zadoks (8 leaves).

Bean (Phaseolus vulgaris L.) is so sensitive to intercompetition especially with weed species. Weed management is an essential factor for the success of an agricultural production system. The use of high competitiveness figures is one of these approaches. Another way to manage properly is just to reduce herbicide dose using through the mixed herbicides in crops. By intercropping, filling the empty space prevents weed development in the area. Mixing or simultaneous cultivation of two or more species in one plot of land is one of the oldest agricultural systems in the world. Planting density is another important factor in determining plant yield. Planting density not only determines competition for light and nutrients, but also controls the distribution and allocation of dry matter between plant organs. The studies showed that by increasing bean planting density from 20 to 30 and 40 plants m2, yield increased by 15.4% and 24.7%, respectively, and the weed biomass also increased by a density of 20 to 40 by 30 percent. The use of high competitive cultivars and increasing planting density are the main strategies to increase the competitive ability of beans against weeds. This study was carried out to investigate the methods of pure and mixed cultivation of bean cultivars with different densities for their effect on reduction of bentazone herbicide dose, weed control and crop yield.

In order to investigate the effect of planting density and reducing herbicide doses on weeds biomass and crop yield in pure and mixed cultivation of red bean cultivars, a field experiment was carried out at Agronomy Research Field of Ferdowsi University of Mashhad during 2013 - 2014. A factorial experiment (with three factors) was conducted in a completely randomized block design with 4 replications. Experimental treatments including bean planting densities in three levels consisting of optimum density (Goli 40 and Akhtar 50 /m2), 20 and 40 % higher than the optimum density of both Akhtar and Goli cultivars, and Bentazone herbicide concentrations (0, 50 and 100 %) based on the recommended dose (2.5 liters per hectare), and separate and mixed cultivation of Akhtar (standing) and Goli (ascending) cultivars were performed in rows (1:1). Weed biomass was evaluated every two weeks after spraying by 100*25 cm2 cadaver from two middle rows. At the end of the growing season, a 1*1 m2 staff was used to determine the performance. Data were analyzed by SAS 9.1 software and averages were compared with the LSD test at 5% probability level and the graphs were analyzed using SigmaPlot 12.0 software.

The results showed that for the weed biomass, the mixed cultivation of Akhtar and Goli cultivars was more than pure cultivation due to its success in suppressing high competitive weeds through rapid space cover, which can be attributed to this feature. It was used to reduce the herbicide dose. Also, the highest and lowest grain yield (respectively 463 and 132 g/m2) were found for the pure cultivation of Akhtar cultivar at concentration of 100 and 0 % herbicide, respectively. However, in flowering and mixed cultivars, the highest grain yield was observed at 372.2 and 341.3 g/m2, at 50% herbicide concentration, which was also observed in biological yield. Results of interaction effect showed that the highest biological yield in intercropping (1166 g/m2) was observed for 50% herbicide concentration and 40% planting density. It can be, therefore, concluded that reduced doses of herbicides can only be used if the crop has high competitive ability and planting density is increased, which can reduce the competitive ability of weeds. The use of high competitive crops and increased density of crops have the greatest potential in suppressing weeds and reducing herbicide dosage. The previous studies also showed that limiting bean growth leads to a decrease in leaf area index and bean growth rate, which in turn reduces its competitiveness against weeds.

The use of high-strength cultivars in mixed cultivation due to their overlap, space conquest, and ability to compete with weeds along with increased plant density has a high potential for weed suppression and can be used in other ways to reduce herbicide dose. The results of this experiment showed that there was no significant difference between biological yield at 50% and 100% herbicide concentrations in the mixed cultivation and the highest biological yield was observed in the mixed cultivation.

Recognition of Eryngium caeruleum germination biology can provide the possibility of forecasting the seed dormancy and germination level in various conditions. This study was conducted as factorial experiment based on completely randomized design with three replications in the laboratory of Agronomy and Plant Breeding Department, College of Agriculture and Natural Resources, University of Tehran, to understand Eryngium caeruleum seed dormancy and response of germination thermal parameters. The experimental factors were included three levels of gibberellic acid (0, 250, 500 mg/l), six chilling time (1, 3, 5, 10, 15, 30 days) and seven temperatures (5, 10, 15, 20, 25, 30, 35°c). Germination parameters were obtained by the segmented model under the influence of gibberellic acid and chilling treatments. The results of this study showed that, the best treatment for reducing dormancy level, cardinal temperatures for germination including base, optimum and ceiling temperatures was obtained 1.81, 22.31, and 34.10°c respectively. Increasing of the chilling time and the gibberellic acid concentration from 0 to 250 mg/l, decreased the base temperature, and increased optimum temperature. Ceiling temperature, at first was increased and then decreased.

To evaluate the effects of bromicide AM (bromoxynil + MCPA)alone or mixed by salicylic acid, cytogaite, and ammonium sulphate on chlorophyll a</em> fluorescence (ChlF) of redroot pigweed (Amaranthus retroflexus </em>L.), a greenhouse experiment was conducted in randomized complete block design with three replications in Agricultural Faculty of University of Tabriz in 2017. Bromicide AM, 16 hours after application, increased minimum fluorescence (F0</sub>) 84%, thermal dissipation quantum yield (F0</sub>/Fm) 89% and the rate of accumulation of closed reaction centers (∆V/∆to</sub>) 59% and decreased maximum fluorescence (Fm) 40%, maximum quantum yield of photochemistry (Fv/Fm) 71%, electron transport yield (φEo</sub>) 94%, normalized area (Sm) 97% and time needed to reach Fm (Tfm) 89%. Salicylic acid as a growth regulator had not negative effect on the efficacy of bromicide AM. 64 hours after herbicide application, synergistic effect on bromicide AM ammonium sulphate and cytogaite reduced 52% and 45% Fm, 62% and 37% Fv/Fm, 25% and 11% Fv/ F0</sub>, and enhanced 6% and 3.5% F0</sub>/Fm, 72% and 25% specific fluxes expressed per reaction centers (ABS/RC), 83% and 30% ratio – flux of dissipated energy per reaction center in t = 0, respectively. Results showed that assessment of chlorophyll a</em> fluorescence is a rapid and non-destructive technique for detecting photosynthetic apparatus response of plant to applied herbicide alone and or mixing with adjuvants.

Eryngium caeruleum L. is a perennial weed from Apiaceae family that grows in the farm and roadside. There is limited information on the reaction of this plant germination to temperature and light conditions. Germination is one of the most important processes for weed success, because it is the first step in competition beginning in an ecological niche. Recognition of E. caeruleum germination and emergence ecology has an important role in weed management and control. Different environmental factors, such as temperature and light, affect dormancy and germination of the seeds. Light requirement is an indicator showing the level of seed dormancy. Given the significance of seed dormancy in weed dispersal and management, this study aimed at determining the relation between light and temperature as the most effective environmental factors in germination stimulation of E. caeruleum. An experiment was conducted to estimate the effect of temperature and light on germination of Eryngium caeruleum seeds at agriculture and Natural Resources College, university of Tehran in 2016. A factorial experiment was undertaken based on completely randomized block design with three replications. Factors were germination temperatures (5, 10, 15, 20, 25, 30 and 35 °C), burial periods in 5 cm depth (30, 60, 90, 120, 150, and 180 days), and light conditions during germination test (Presence and absence of light). The seeds were buried in the soil under environmental conditions at depth of 5 cm and then removed from the soil at one month intervals and were placed at dark and light (Osram, L 18 W/77, 20 µmolm-2s-1) conditions under seven temperature treatments for 14 days. 25 seeds were placed in each petri dish and the germinated seeds were counted for 14 days in each month. Segmented model was used for studying the germination rate to temperature in light and temperature treatments. Thermal parameters of germination were calculated for light and temperature treatments. These parameters were Gmax for the maximum germination rate, Tb or base temperature for germination, To or optimum temperature for germination, and Tc or ceiling temperature for germination. The base and ceiling temperature parameters were also calculated. The findings of this study shed light on seed germination requirements of E. caeruleum and enhance our understanding of this species distribution. These results will be useful in selecting the best time and method for E. caeruleum control. Results showed that temperature and light conditions during germination test influenced germination rate. According to the analysis of variation, all simple effects and interactions were significant on germination rate. Germination rate increased with increasing temperature up to 20 °C. Germination rate, however, decreased when temperature increased up to 35 °C. Temperature parameters of base temperature, optimum temperature and ceiling temperature were affected by burial periods and light conditions during germination test. In general, base and optimum temperatures decreased and ceiling temperature increased with increasing of burial time. The burial time needed for 50 percent decrease of maximum base temperature in the lowest burial time was 117 days in light condition and 82 days in dark condition. The optimum temperature decreased from 23.5°C to 21.2°C in light condition and from 23°C to 21°C in dark condition. The ceiling temperature increased from 28°C to 42°C in light condition, but it had different process in dark condition. The Tc parameter was 30°C in 60 days of burial and was 28°C up to 120 days of burial and had no changes up to 180 days of burial. Parameters of Gmax and ai, which indicate the maximum germination rate and seed non-dormant index, respectively, rose linearly by increasing time of seed burial, irrespective of light condition during germination test. The same results were found in Circium arvense and Bidens pilosa, that their germination thermal parameters were higher in light condition than in dark. This can be attributed to the heat made by the light. The results of the experiment on Plygonum aviculare also showed the effects of light on cardinal temperatures of germination and the start of germination of this plant. The results showed that the thermal parameters of Eryngium caeruleum germination including base temperature (Tb), optimum temperature (To), and ceiling temperature (Tc) changed during the burial periods. The Gmax and awakeness index parameters increased linearly regardless of the presence or absence of light. It can be also concluded that Eryngium caeruleum L. has morphophysiological dormancy and dormancy breaking. Moreover, the optimum temperature range for germination mostly rises by increasing ceiling temperature.

In order to assess the effects salicylic acid (SA) on corn, weeds, and some herbicide efficiency, a factorial experiment with two factor as randomized complete block (RCB) designed with three replications was conducted research field of university of Tabriz- Iran in 2015. The first factor 10 levels including 8 herbicide treatments (Bentason, Nicosulfuron, 2,4-D + MCPA, Bromoxynil + MCPA, Rimsulfuron, Nicosulfuron + Rimsulfuron, Mesotrion + S-metolacholor + Terbuthlazine, Udosulfuron + Foramsulfuron + Tincarbason), and 2 controls treatments (weed free and weed infest), and the second factor was SA with 2 levels (0 (distilled water), and 1 mM SA). Results show that SA can increase corn leaf area, and dry weight of leaf and stem. This increase was outstanding in herbicides that could successfully control weeds. SA in weed infested treatment, increased common lambesquraters (Chenopodium album L.) density and dry weight, as the main weed species observed in the field. So in presence of weeds, SA is more benefit for weeds. Nicosulfuron was weak in weed control, and SA application increased weeds density and dry weights. Bromoxynil + MCPA, Mesotrion + S-metolacholor + Terbuthlazine, and 2,4-D + MCPA were successful herbicides in reduction weeds density and dry weight, and their efficiency was not reduced in presence of SA. Therefore, in herbicide treatments with weak efficiency in weed control, usage of SA is more benefit for weeds. According to obtained results, applying SA is not recommended with weak efficiency herbicides in weed control.

To evaluate the response of annual weeds to interaction between imazethapyr herbicide doses and soil moisture in beanfields, a split plot experiment based on randomized complete blocks design with three replications was conducted. Main plots included three different moisture regimes (60, 75 and 90 mm of accumulated evaporation; equal to 100, 80 and 60% of bean water requirementrespectively) and sub-plots were five doses of imazethapyr (0, 25, 50, 75 and 100 percent of the recommended dose). The result illustrated that the interaction effects of herbicide doses and soil moisture on the biomass of weeds were significant. Under low soil moisture conditions, Amaranthus retroflexus and Chenopodium album grew more and the highest amount of weed biomass (396. 81 gr /m2) was obtained from 60% of bean water requirement and without weed control treatment. Also, based on the three-parameter dose-response model, the predicted ED50 parameters in the 100, 80 and 60% moisture regimen, were 32. 45%, 56. 59% and 73. 46%, of the recommended dose respectively. These results showed that in the less soil moisture, the amount of required herbicide to reduce the 50% of weed biomass, increased. The highest yield (4133. 84 kg/h) was obtained from 100% moisture regime and 100% recommended dose of herbicide. According to these results, when soil moisture content is appropriate, the herbicide efficiency in weed control and also the bean yield will increase. The results of this experiment can be used to predict the appropriate dose of herbicide in variable climatic conditions of Iran.

Pondweed tolerance to flooding and most herbicides, as well as regrowth after hand weeding, has led the weed to be considered as an invasive species in paddy rice. Three experiments were carried out to provide a strategy for management of pondweed. In the first experiment, the interference of pondweed with Hashemi and Gohar rice cultivars at 0, 50, 100 and 150% of recommended NPK fertilizer were studied. In the second experiment, pondweed proliferation and colonization at the above fertilizer levels; and in the third experiment, the effect of water depth on the growth of this weed were investigated. The result of the first experiment showed that pondweed does not have significant effect on the yield of Gohar cultivar, but decreased the yield of Hashemi by 13-25%. Decreasing the fertilizer level to 50 and zero percent of recommended doses led to sharp decline in the performance of both rice cultivars in competition with pondweed. According to the results of the second experiment, the pondweed colony expansion in the 50% recommended dose of fertilizer treatment was twice that of 100% fertilizer treatment. The result of third experiment showed that, increasing the water depth to 7 and 14 cm led to 359 and 342 percent increase in pondweed shoot biomass in comparison to saturated treatment. In general, according to the results of this research, the reason for the outbreak and damage of pondweed can be attributed to the nutritional weakness and the deep and long flooding of the paddy fields. In case of efficient use of fertilizers, drainage and the use of appropriate cultivars, it is not necessary to spend a lot on frequent hand weeding and the presence of weed will not cause significant economic losses of rice.

Wild oats seed is dormant and seeds can persist in the soil for a long time. Factors that influence germination are temperature, seed position and seed coat. Thus, laboratory experiments were conducted at University of Tehran, Collage of Agronomy and Plant Breeding, to study the effect of temperature, seed positin and seed coat on seed germination of four population of Avena ludoviciana. The experimental design was a completely randomized design with factorial arrangement of treatments with three replications. Experimental treatments were seed position (lower and upper seeds), temperatures (5, 10, 15, 20, 25 and 30 ◦c). Response of germination rate against temperature was described with sigmoid function for each population. The results in laboratory showed that the lowest germination percentage (GP) and germination rate (GR) were obtained in Qaemshahr primary and secondary seed without coat, with lowest seed weight among all populations studied. Big seed without coat had higher germination percentages (%80) than small seed (%56) in Qaemshahr. In contrast, Kamyaran with highest seed weight had higher germination percentages and germination rate. In Kamyaran population big seed without coat had higher germination percentages and germination rate than small seed. . Decreasing in GP and GR in seed with coat compare to seed without coat in Marvdasht and Mahidasht, were observed. However, management plans could be proposed at regional scale according to the approach of modifying the patterns of agronomic to which the local populations have adapted.

This study was conducted to evaluate the effect of temperature and moisture on germination of Eryngium caeruleum seeds as factorial experiment in a completely randomized design with three replications at weed science laboratory, college of agriculture and natural resources, university of Tehran. Factors were seven temperatures (5, 10, 15, 20, 25, 30 and 35°c) and seven levels of moisture (0, -2, -4, -6, -8, -10 and -12 bar) and hydro thermal time model used for description of Eryngium caeruleum germination. Germination parameters including base temperature (Tb), optimum temperature (To), the minimum moisture needed for start of germination (Wpb), decreasing coefficient (b) and standard deviation (Sigma) were obtained 2.39, 23.52, -0.93, 0.13 and 0.34 respectively, affected by different levels of temperature and moisture by using hydro thermal time model. The results also showed that germination percentage and rate increased up to -4 bar in base temperature and these germination characteristics reached to their highest level in optimum temperature. According to the results of this study, it can be said that the seeds of Eryngium caeruleum do not have resistance to the water stress at very low and very high temperatures, and have the maximum resistance at 20°c

A precise prediction of the phenological development of weed species in crops would provide timely control for more efficient management of weeds. In order to study, experimental design was a randomized complete block split-split-plots conducted in 2012-2013 at agricultural reaserch field of University of Tehran located at Karaj, Iran. With five planting dates (26Mehr, 14 Azar, 30 Day, 24 Esfand and 4 Ordibehesht) as the main plot treatments. The main plots were split with two moisture conditions (irrigated and rainfed) as subplots. Each subplot was further split with six population (Ahvaz, Shiraz, Qaemshahr, Karaj, Kamyaran and Kermanshah). Time to main phonological stages of the A. ludoviciana populations including emergence time, tillering, heading and maturing were compared using linear regression and multivariate methods. Comparing among populations, emergence rate in two population of Kamyaran (0.11) and Karaj (0.1) was higher than the other populations. Kamyaran population with average less temperature spent each stage of phenological development. A clear clustering was obtained based on rates of phonological development and location characteristics of the population’s origin. Kamayaran and Kermanshah populations were in one cluster, karaj and shiraz were more similar, and mazandaran and Ahvaz showed significantly different from other populations. Kamyaran and Kermanshah showed a higher correlation in the weight of seeds, rate of emergence, and altitude. Ahvaz population showed close relations with temperature. In the Mazandaran population the highest tillering rate and stem elongation rate occurred. Also GDD could use for precision time of application of herbicides and could recommend minimum herbicide application, after optimization of the application, the use of such pesticide would be environmentally safe, Due to the simultaneity of the growth of wild oat and wheat.

Photosynthesis in plants is strongly influenced by stress. Evaluation of chlorophyll a fluoresce is one of the methods for assessment the different stresses effects such as herbicide on photosynthesis. Application of plant growth regulators like salicylic acid (SA), is one of the strategies to overcome for physiological disorders in plant. Therefore, to study the effect of SA mixture with Bentason, Bromoxynil〣 and 2,4-D〣 herbicides on physiological behavior of Common lambesquarts (Chenopodium album L.), a greenhouse experiment was conducted in randomized complete block design with three replications in Agricultural faculty of University of Tabriz in 2016. The results indicated a reduction in maximum fluorescence (Fm), variable fluorescence (Fv), maximum quantum yield of photochemistry (Fv/Fm), efficiency of the water-splitting complex on the donor side of PSII (Fv/Fo), and performance index (PIABS), and an increase in minimum fluorescence (Fo) and photosystem II antenna (Fo/Fm) of Common lambesquarts subjected to Bentason and Bromoxynil〣. Dry weight and chlorophyll index in control treatment (without SA) increased 4.3% and 2.1% respectively, but in Bentason and Bromoxynil〣 and 2,4-D〣 treatments, these two indexes reduced 41.6%, 13.7%, 13.6% and 32.2%, 36.4%, 18.7%, respectively. SA not only did not reduce the Bentason and Bromoxynil〣 efficiency, but also increased efficiency of these two herbicides.

Field experiments were conducted to study the effect of nitrogen, wheat density and herbicide doses on wheat-wild barley competition in Karaj and Qom. Experiment was a split-factorial with three replications. Experimental factors were wheat densities of 300, 400 and 500 plants m-2, nitrogen levels of 240 and 300 kg ha-1 and five doses of metsulfuron-methyl plus sulfosulfuron at 0, 20, 33, 45 and 54 g ha-1. Results from both locations indicated significant interactions between treatments. Depending on herbicide dose applied wheat density effect on wild-barley biomass was different. Decrease in wild-barley biomass obtained from increasing wheat density was significantly higher with low doses of herbicide. Regarding higher nitrogen efficiency in Karaj wheat, lower nitrogen level caused more competition ability of wheat and lower wild-barley biomass. In Qom experiment, the general trend was similar, differences were not significant at p-value

Chemical weed control is a main component of management programs of crop productions. Timely herbicide application significantly increases herbicide efficiency. A field experiment was conducted to study the effect of Nicosulfuron timing and dose on S. halepense competition with maize. Experiment was split-plot in three replications. Main plots were herbicide dose of 0, 1, 1.5, 2, 2.5 kg/ha and sub plots were herbicide timings of 2-4 l, 4-6 l, 6-8 l of maize growth. Growth parameters of maize including height, leaf area (LA) and total biomass (TB) were measured. Results showed, the highest height, LA and TB were obtained from Nicosulfuron application at 1.5 Kg/ha in 2-4 l of maize and no significant difference was shown to herbicide recommended dose or higher. With delay in herbicide application, the height and TB of S. halepense increased and its competition with maize got raised. It caused decrease in maize growth indices. Current study showed main effect of herbicide dose in changing weed-crop interactions. Successful management would change competition in advantage to crops using lower herbicide doses to achieve both economic and environmental purposes in sustainable crop protection.

Intercropping has many advantages including improved soil conditions (Chen et al., 2004), increased resources and better weed control (Banik et al., 2006). Due to their positive effect on forage quality, intercropping of cultures has an important role in farming systems. Furthermore, intercropping improves absorption of solar radiation, increases the activity of soil microorganisms and contributes to better weed- and pest-resistant conditions (Karadage, 2004). The goal of this research is to investigate intercropping of maize and sorghum with legumes, such as mung beans, cowpeas and clover, in order to evaluate the benefits. The benefits should include increased yield, improved quality forage (higher protein levels), and better weed control. Intercropping should best suit the climatic conditions of the region and improve agricultural practices.
In order to investigate the effect of additive intercropping of maize and sorghum with legumes on qualitative and quantitative forage and weed growth, a field experiment was carried out over two years, in the 2011-12 growing seasons in the village of Mafin-Abad, in the Eslamshahr region of Tehran Province. Maize and sorghum monoculture and their intercropping with three different legumes (mung beans, cowpeas and berseem clover) in different additive intercropping systems were compared in a randomized complete block design (RCBD) with three replications. The traits evaluated in this study include yield, forage dry matter, protein, index against ground, and economic advantages.
The results showed that intercropping increased forage dry matter and crude protein. Intercropping also significantly decreased weed dry weight. In all intercropping treatments, LER was above 1, indicating yield advantages for intercropping. Maize and cowpeas in the 100% density treatment showed the best results over both years and produced the highest dry forage yield, LER and CP and the least amount of weed dry weight. Based on the results of this experiment, it could be concluded that maize and sorghum-legume intercropping could substantially increase forage quality and quantity. These intercrops can be recommended to replace monoculture systems. Maize and sorghum-cowpea additive intercropping could be highly recommended because of higher forage quality and quantity with fewer side effects on the environment.
The results showed that intercropping could be used to increase yield, improve forage quality and weed control. Intercropping cultures also indicated that LER was more than 1 and led to a higher economic profit in comparison with a monoculture. This can be a suggestion for farmers to use intercropping in this recommended form. In the intercropping of maize and sorghum and cowpea, particularly with a density of 100%, cowpea clearly manifests itself. Therefore, intercropping can be recommended to farmers as a way to boost performance, revenue, forage quality (protein) and control weeds.

Photosynthesis is an essential part of the plant function and metabolism and a number of herbicides inhibit certain photosynthetic activities. The aim of this study was to evaluate the effect of some herbicides including Topik, Titos, Equip, Mister, Lumax, Bromicide and Oltima on the photosynthetic efficiency of three corn cultivars (CC-260, 400, 704) in response to salicylic acid (SA) treatment via chlorophyll a fluorescence (ChlF) transient curve (OJIP) analysis. Result showed that Topik, Titos, Equip, Mister and Oltima herbicides had no effect on the ChlF. In contrast, Bromicide and Lumax changed the shape of the ChlF curve as I phase of the OJIP curve was lost and the fluorescence level in the J step was close to I stape. However, application of SA improved the shape of the OJIP curve similar to normal samples. SA application under Bromicide and Lumax treatments un-blocked the electron transfer between QA and QB of PSII. Our study clearly indicated that the effect of SA on the I-P part of the ChlF curve was more than other parts. Thus, the effect of SA on the PSI activity was more than that of PSII under these herbicide treatments.

Kermanshah province, Iran, comprises an area, of 24640 km2 and is located between 33°37′-35°17′N and 45°20′-48°1′E. The average annual precipitation is 450 mm. Most of the fields surveyed in this study lie between 542 and 1554 m a.s.l. Among the factors decreasing the wheat yields, weeds have an important role. The results of some researches show that the weeds flora depends on climatic conditions, temperature and amount of rainfall in spring and in summer. Environmental factor splay a key role in the weed cover. These differences affected by climatic conditions, latitude and longitude. Multivariate statistical methods that have been addressed in this study area powerful tool to study the relationship between environmental factors and ecological weed community composition (Hassannejad & Pourhaydar Ghafarbi, 2013; Lososova et al., 2004). Correlation and regression of data floristic and environmental factors were used in the CCA (Canonical Correspondence Analysis) technique (Legendre & Legendre, 1998).
A survey was conducted to study the effects of soil and climatic factors on distribution of weeds in 85 irrigated wheat fields in 11 counties based on its area under irrigated wheat. An Experiment was conducted in Kermanshah province during 2011-2012. After choosing the field to be surveyed, the surveyor followed a “w”-designated set pattern to enumerate the weeds in each type of field. The pattern and number of 0.25 m2 quadrats varied according to the size of the fields. The field surveys were made during the wheat tillering to stem elongation stages. Frequency, density and mean density index of species in each county were calculated. After weed species were collected in the fields, we arranged the samples into the first matrix where weed species are represented by columns and fields of different districts by rows. Also, in the second matrix, environmental factors are represented by columns and fields of different districts by rows. Data on weed communities and environmental factors of all districts were analyzed through with ordination methods like canonical correspondence analysis (CCA) and weed species distribution and environmental factors displayed in ordination diagrams. These ordination methods were done with mean density of 29 abundant weed species for CCA using CANOCO (Version 4.5). Ordination plots were produced for both sampling sites and weed species associated with environmental factors. For CCA, we used site elevation, humidity for 10 years period, daily raining for a 10 years period. Soil characteristic included calcium, phosphor, potassium, nitrogen, sodium, magnesium, pH were determined. Sand, clay and silt in soils were measured and elevation of each field was gained by GPS.
162 weed species belonging to 33 plant families were identified in these fields. Multivariate analyses with canonical correspondence analysis (CCA) showed that changes in the weed species distribution were due to soil characters (pH, Calcium, Magnesium, Phosphorus, Nitrogen, Sodium, Potassium, silt percent, clay and loam in soil tissue, cation exchange capacity, EC) and environmental conditions during former years. The first and second RDA axes described 64% of variations in the weed populations affected by climatic factors. Winter wild oat (Avena ludoviciana L.), ryegrass (Lolium rigidum Gaud.), wild mustard (Sinapis arvensis L.) and canary seed (Phalaris brachystacys Link.) in areas of high temperature and low altitude, had a wide distribution. High evaporation increased wild barely (Hordeum spontaneum C. Koch.), Corn cleavers (Galium tricornutum Dandy.) and Vetch (Vicia assyriaca Boiss.) density during last decade. Where the soil nitrogen and phosphorus rates were high, Wild barely (Hordeum spontaneum C. Koch.) density was found frequently in wheat fields of Kermanshah. In the wheat fields of Kermanshah, Bindweed (Convolvulus arvensis L.) and wild safflower (Carthamus oxyacantha M. B.) were more abundant in clay soils. High Corn cleaver (Galium tricornutum Dandy.) density was found in alkaloid and sandy soils.
Generally predict that if the temperature rise over the next few years, weed density and abundance of wild oat, ryegrass and wild mustard will be increased in irrigated wheat fields.
Acknowledgments
The authors acknowledge the financial support of the project by agricultural Research education and extension organization and College of Agriculture and Natural Resources, Tehran University.

Experiments, in Petri dish and greenhouse, were carried out to investigate the efficiency of three herbicides (rimsulfuron, imazapic and imazamox) in controling broomrape. In Petri dish study, herbicides were applied at 0.05, 0.25, 1.25, 6.25 and 31.25 micro-mole doses to broomrape seeds at germination stage without a host plant and adding GR24 as stimulator. In the greenhouse experiments, the efficiency of these herbicides to control broomrape in two varieties of tomato (Viva and Hyb.Petopride II) was investigated. Treatments were four doses of rimsulfuron (25, 50, 75 and 100 g ai/ha), imazapic (5, 10, 15 and 20 g ai/ha) and imazamox (0.4, 0.8, 1.2 and 1.6 g ai/ha) at one, two and three applications. Results of Petri-dish experiments showed that rimsulfuron and imazapic significantly reduced radicle elongation of seedlings as compared to the control, while, imazamox did not have any effect on broomrape seed. Each dose was applied for one, two and three times with in 15, 29 and 43 days after within transplanting tomato seedlings. Results of pot experiments indicated that the responses of two tomato varieties herbicides were different. Viva was responsive to herbicidal effect and produced higher biomass than Hyb.Petopride II. Rimsulfuron was a suitable herbicide in tomato to control broomrape. Rimsulfuron at doses of 25, 50 and 75 g ai/ha (three times of application) were the best doses, specially in viva were the best treatments for broomrape control and producing tomato biomass. Imazapic also, at 5 g ai/ha (two times of application) and 10 g ai/ha (single application) was an effective treatments in variety of viva. Imazamox treatments did not appear to be suitable herbicides in this study.

To evaluate post-dispersal seed predation of weeds in maize fields، factorial experiments with four replications were conducted in 2007 in Mashhad and Chenaran، NE of Iran using four common weed species in maize field. Treatments were weed species، sampling periods and cages. Removal of Amaranthus retroflexus، Chenopodium album، Sorghum halepense and Datura stramonium were measured during seven sequential weeks in two maize fields from August until October 2007 Wire mesh cages were used to determine the predation by avian predators. Invertebrate seed predator activity-density was monitored using pitfall traps. Seed removal was significantly different between fields and among species. Post-dispersal seed predation was higher in Chenaran maize field (55درصد) than Mashhad field (47درصد) that could be resulted from difference in irrigation method and the number of invertebrate predators. Except some fluctuations during the predation period، seed removal decreased toward the end of experiments in both places. Cage exclusion had no significant effect on predation in both places، showing no significant removal of seeds by birds. Invertebrates were the most important predators in both fields and ants were the main invertebrateseed predators but other seed eater invertebrates like crickets and different seed eater carabid beetles were caught in to pitfalls too

A two-year field experiment was conducted in 2007 and 2008 to determine the relationship between competitive indices of maize, Xanthium strumarium and Amaranthus retrolexus. Five doses of herbicide nicosulfuron as the main factor, and a combination of 16 densities comprised four densities of A. retroflexus × four densities of X. strumarium as sub plots were arranged in a one-replicate split factorial. Four indices were considered for maize which is influenced by competition: grain yield, biomass, leaf area, and plant height. Biomass was determined as the direct factor that controlled grain yield, and the biomass was directly depended on maize leaf area. The plant height had the most important role in the maize leaf area. Field observations confirmed the efficacy of plant height in evaluating the plant competition. Increase in X. strumarium biomass indicated direct effect on maize grain yield. The X. strumarium biomass was controlled by its leaf area and the number of lateral shoots. However, the plant density as an external factor had significant effect on crop-weeds competition, herbicide dose was determined the most important determinant that caused major change in the X. strumarium height and leaf area. Among the A. retroflexus indices, its leaf area was the most effective, which was directly controlled by its biomass. Deep understanding of the system behavior, relations and interactions with herbicide is a great help in managing the weed damage.