نشریه دانش علفهای هرز
سال سیزدهم شماره 1 (بهار و تابستان 1396)

In order to investigatsion of integrated management of mesquite, an experiment was conducted with 16 treatments in randomized compelete blocks design with 3 replications at Yazd province during 2010-2014. Treatments included: Glyphosate at 6, 8 and 10 Lit.ha-1 one time and Glyphosate at 3, 4 and 5 Lit.ha-1 two times; 2,4-D〣 at 2 and 4 Lit.ha-1 one time and 2,4-D〣 at 1 and 2 Lit.ha-1 two times. Integrated treatments include 2,4-D〣 plus Glyphosate at 1 and 2 Lit.ha-1 two times; 2,4-D〣 plus Glyphosate at 2 and 4 Lit.ha-1 one time; cutting one time; cutting 2,4-D〣 at 2 Lit.ha -1 ; cutting Glyphosate at 4 Lit.ha-1 and Control with no treaetment. Results of the 3 years experiments showed that the treatments of cutting, cutting (2,4-D〣) at 2 lit.ha-1 and cutting Glyphosate 4 lit.ha-1 decreased the dry weight of mesquite in acceptable quantity. The highest percent control of mesquite was observed in 2,4-D〣 (2 lit.ha-1) Glyphosate (4 lit.ha-1), with 97.78% ; 2,4-D〣 (1 lit.ha-1) Glyphosate (2 lit.ha-1) with 97.22% and 2,4-D〣 (4 lit.ha-1) with 85.00 %. Based on the results of 3 years of the experiment the lowest of dry weight observed in cutting treatment and 2,4-D〣 at 2 lit.ha-1 two times; 2,4-D〣 4 Lit.ha-1 and 2,4-D〣 1 Lit.ha-1 two times with 1.09, 2.12, 4.37 and 4.57 gr. respectively.

A series of laboratory tests were conducted on wild wheat and wild barely, collected from dryland wheat farms of Lorestan province to determine the effect of temperature on their germination and emergence. Treatments included tempereatures raging 0-40 °C. According to the two segments equations fitted to the trend of seed germination, different constant temperatures, base temperature, optimum temperature and maximum temperature for germination of wild wheat intact seed with seed coat (lemma and palea), were estimated at 0.79, 24 and 28 °C respectively, as for wild barley were estimated at 0.82, 30.6 and 36 °C respectively. Average emergence of wild wheat intact seeds planted in the soil at six fluctuating temperatures of day/night regimes was 71.3%. A average of wild wheat dehusked and intact seeds germination in Petri dish experiments for six fluctuating temperatures of day/night regimes, were 70.5 and 17.9 percent respectively. In the case of wild wheat, intact seeds for day/night regimes of 10/1, 30/10 and 35/15 °C seed germination did not happen, and maximum seed germination (79%) was achieved for the 15/10 °C temperature regime. Under these conditions, wild wheat intact seed germination mean of 20/5 and 25/10 °C temperature regimes were 14 percent. The lower mean germination of wild wheat intact seeds with lemma and palea in the testing germination in Petri dishes compared with the mean of dehusked seed germination without lemma and palea, and the emergence mean of intact seeds planted in the soil suggest existence of probable inhibitor substances in the seed coat, that under soil conditions are leached from the surrounding environment of the seed.

Japanese brome (Bromus japonicus Thumb.) is the most important winter annual grass weed in the wheat fields of Sistan & Baloochestan province. During 2013-2014 and 2014-2015 growing season at Zahak Agriculture and Natural Resources Research Station, Zabol, field experiments were conducted to investigate the effect of rate and time of sulfosulforoun application in order to control Japanese brome in different wheat cultivars. Three wheat cultivars (Hirmand, Kalak Afghani, Sistan), three stages of herbicide application (2-3 leaves, 4-5 leaves, tillering of B. japonicus) and four herbicide doses (control, 17, 22, 22 gr. ha-1) of the commercial form of Apirus 75% were arranged in a factorial experiment under a randomized completed blocks design.Japanese brome density and dry weight were measured 30 days after final herbicide application. We also evaluated biological and grain yields of wheat at harvest. In all cultivars, herbicide application at 4-5 leaves and tillering of Japanese bromeshowed the highest and lowest weed density and dry weight respectively. Based on a logistic model fitted to density data of Japanese brome, the estimated dose to 50% loss in Hirmand at tillering stage was more than labeled-recommendation dose of sulfosulforoun ( =28.3). The grain yield values in Hirmand and Kalak Afghani cultivars showed the highest and lowest in response to. Japanese bromedensity, respectively.

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

To evaluate the effect of false seedbed preparation on rye (Secale cereale L.) control, an experiment was conducted during 2013 in Shahrekord. Experimental factors were arranged in split plot factorial design with three replications. The main plots included seed bed preparation at three levels: 1. conventional dry cultivation of wheat, 2. seedbed preparation, irrigation, weed control (including rye) with paraquqt (20% SL) at 2 L ha-1 after one month, wheat cultivation, 3. seedbed preparation, irrigation, mechanical weed control (using harrow), wheat cultivation. Subplots 1. included cultivars at three levels (Alvand, Pishgam and Back Cross Roshan) and 2. planting densities at three levels (200, 250 and 300 kg ha-1). According to the mean comparison, density and biomass of rye in the treatment of irrigation application of herbicide decreased relative to dry cultivation by 67.7 and 74.9 percent, respectively, Pishgam cultivar decreased rye density and biomass by 36.9 and 18.7 percent, respectively. The seeding rate of 200 kg ha-1 of wheat reduced density and biomass of rye by 24.3% and 22.4%, respectively. The highest grain and biological yield of wheat was observed in irrigation and application of paraquat with 4206 and 8872.3 kg ha-1, respectively. Based on the results of this research, for weed control, especially rye, yield and yield components of winter wheat, the best method of seedbed preparation, is false seedbed preparation using chemical control of weeds. The best wheat cultivar, was Pishgam and best wheat seeding rate, was 200 kg ha-1.

In order to evaluate the competitive ability of rice genotypes against weeds in direct seeding system and determination the traits that may confer such attributes, a field experiment was conducted at the Rice Research Institute of Iran in Rasht during 2016-17 cropping season. The experiment was laid out in a split plot based on randomized complete blocks design with three replications. The treatments included two levels of weed management (weedy (under natural weed flora) and weed-free) as the main plots, and ten rice genotypes (Hashemi, Abjiboji, Tazeh Hasani, Gilaneh, Shiroodi, Saleh, RI18430-1, RI18430-60, RI18430-72, RI18430-77) as subplots. The results showed genotypic differences in competitive ability against weeds. Under weed- free conditions, grain yield varied from 3293.5 in Saleh to 6796.1 kg.ha-1 in Shiroodi. Under weedy conditions, grain yield was also registered from 260.6 in breeding line RI18430-72 to 1291.2 kg.ha-1 in Hashemi. The highest and lowest amounts of weed biomass at flowering were also observed in Abjiboji and shiroodi, respectively. Average yield loss due to weed competition ranged from 73.55 to 94.1% in different rice genotypes. The results also indicated a positive significant correlation between competitive ability and grain yield, thus Hashemi, Shiroodi and the breeding line RI18430-60 had the highest competitive ability against weeds and also grain yield (the basis for direct selection under weedy condition). This method can be applied in integrated weed management programs to reduce herbicide use. The study revealed that early growth (vigor), leaf area index, crop biomass and height had significant positive correlation with competitive ability and hence, can be used as useful indirect selection criteria of genotypes with high competitive ability.

Knapweed (Centaurea balsamita Lam.) is an annual winter weed in Asteraceae. It is expanding in winter cereal fields of Iran. During 2015, an experiment was conducted in the Weed Science Laboratory, Department of Agronomy & Plant breeding in the College of Agriculture and Natural Resources, University of Tehran. Different levels of osmotic potential, salinity, PH, KNO3, GA3 and burial depths at 20 ̊C were evaluated. Results showed that C. balsamita has a good tolerance to drought stress (-0.76 MPa), but it is sensitive to soil salinity. The best pH is neutral for germination. C. balsamita seeds reacted to KNO3 and GA3 treatment well. By increasing KNO3 and GA3, germination percentage raised. This weed grows in shallow depths (3 cm). Most germination occurs at the soil surface. Deep plowing is, therefore, recommended to prevent seed germination.

In order to investigate the effect of codacide adjuvant on the efficacy of clodinafop propargyl and tribenuron methyl, a field experiment was carried out on wheat at the Iranian Research Institute of Plant Protection in Alborz province during 2013-2014 growing season. Treatments included tribenuron methyl at three doses (10.5, 12.75 and 15 g a.i. ha-1), tribenuron methyl at three doses (10.5, 12.75 and 15 g a.i. ha-1) 0.25% V/V codacide, clodinafop propargyl at three doses (0.048, 0.064 and 0.08 L a.i. ha-1), clodinafop propargyl at three doses (0.048, 0.064 and 0.08 L a.i. ha-1) 0.25% V/V codacide, and weed-free control. Herbicides were sprayed at tillering stage of wheat. Results showed that clodinafop propargyl at 0.08 L a.i. ha-1 performed better regarding grass weed control and application of codacide adjuvant with this herbicide increased its efficacy. Application of tribenuron methyl (12.75 g a.i. ha-1) codacide resulted in highest reductions in broad-leaved weed density and dry matter (95% and 93%, respectively), which was not significantly different with weed-free control. Wheat biological yield (3275 kg ha-1), grain yield (2200 kg ha-1) and the number of fertile spikelets/spike (6.26) were 22, 40 and 13% higher than the weed-infested control, respectively. The lowest yield among herbicide treatments belonged to tribenuron methyl (10.5 g a.i. ha-1) with harvest index of 34.04% and 36.50 fertile spikelets/spike.