نشریه دانش علفهای هرز
سال هفتم شماره 2 (پاییز و زمستان 1390)

An expiment was conducted in Lorestan Province to investigate the effect of different densities (0, 1, 2, 4, 8, and 16 plant/ m2) of Ground cherry in sugar beet yield. Experimental design was complete randomized design with three replications. In another experiment the effect of single was evaluated on neighbor sugar beet plants. Results indicated that 2 Ground cherry plants can reduce sugar beet yield as much as 34%. A single Ground cherry plant affects sugar beet plants as far as 50 cm away. When planted adjacent to sugar beet Ground cherry reduces the growth of sugar beet plants by 41%. Ground cherry seems to flower in mid May when acquired about 61 to 75 degree days.

Field experiment was conducted in the College of Agriculture and Natural Resources of Tehran University, Karaj to evaluate the effect of intercropping two soybean cultivars on redroot pigweed biomass. The experimental design was a completely randomized block with factorial arrangement of treatments with three replications. Two soybean cultivars including Kelark (tall) and Interprice (dwarf) were planted in sole and under intercropping in competition with redroot pigweed at (0, 2, 4 and 8 plants/m2). The results revealed that yield of both cultivars were decreased with increasing redroot pigweed density, but the yield of Interprice was reduced 45% more than Kelark. In comparison to Interprice, yield of Kelark in intercropping was higher than sole cropping. LER calculated in intercropping under weed free condition was 1.11. Under intercropping, redroot pigweed had lower LAI (0.58), cumulative dry matter (283 g/m2) and CGR (4.7 g/m2day) compared to when grown with sole crops.

Field experiment was conducted to evaluate competition effect of red root pigweed on growth analysis, light absorption and yield loss of two soybean cultivars under sole and intercropping. A randomized complete block design with three replications was carried out in experimental farm of College of Agriculture, University of Tehran, Karaj. Two soybean cultivars: Clark (tall) and Enterprise (dwarf) were planted under sole and intercropping in competition with redroot pigweed at densities of 0, 2, 4 and 8 plant m-2. The results showed that the decrease of soybean LAI under intercropping was less than of sole cropping in both two cultivars. Clark under intercropping and weed free condition and Enterprise under sole cropping and competing with 8 (pigweed/m2) had maximum (7.6) and minimum of LAI (2.1) respectively. Maximum light absorption in the canopy for Clark and Enterprise were 84% and 64% respectively. Leaf area density in the upper levels of the intercropped canopies were much denser, which resulted in less availability of light to pigweed plants.

In order to investigate the possibility of integrated weed management in corn fields an experiment was conducted in a split-plot with randomized complete blocks design with four replications in Arak Islamic Azad University Research Center during 2008. Treatments were corn density at three levels 70, 80 and 90 thousand plants per hectare in main plots and weed management at five levels including weed free and weed infested controls, one time cultivation, one and two liters per hectare of Nicosolforon. Results indicated that, there was no significant difference between one and two lit/ha of nicosulfuron treatments in high corn density was treatments. Therefore, the best corn density for reducing the dose of nicosulfuron 90,000 plants per hectare. Based on the results obtained from present research, in organic agricultural system, herbicide could be omitted for controlling weeds in corn using on time cultivation at 4-6 leaf stage of weeds plus corn density at 90,000 plants per hectare.

Greenhouse experiments were conducted to investigate the effect of spray adjuvant on reducing carrier water salts on glyphosate and herbicidal mixture2,4,-D+MCPA performance on licorice(Glycyrrhiza glabra L.) in experimental greenhouse of University ofTehran,Karaj in 2010. The effect of adjuvant urea ammonium nitrate (UAN), Diammonium sulfate (AMS), Ammonium thiosulfate (ATS) and Ethylene diamine tetra acetate (EDTA) in Offsetting antagonistic effects of two concentrations (0.01 and 0.1 M) of Clacium (Ca) and Magnesium (Mg) were evaluated in two separate experiments using various doses of glyphosate and herbicidal mixture2,4-D+MCPA. In both experiments, treatments were laid out in a completely randomized design in a factorial arrangement with four replications. Results of this study showed that both ions decreased herbicide performance but Ca ion was more efficient than Mg in reducing the activity of used herbicide. Generally, adding adjutants into spray tank increased efficacy of herbicide and its effects on herbicide performance depended on both spray carrier salts and dose of used herbicide. ATS showed the lowest ability in reducing adverse effects of present salts in spray carrier on performance of the examined herbicides while UAN and AMSwere the most effective adjuvant in enhancing the efficacy of glyphosate and herbicidal mixture 2,4-D+MCPA on licorice. According to the results of this study it could be concluded that ammonium-containing adjuvant, in addition to their chelating properties, increased herbicide absorption. Results of this study demonstrated that licorice tissues may act as a source of antagonistic ions for used herbicide.

In order to investigate the resistance level ofannual ryegrass (Lolium rigidum) biotypes to Pinoxaden herbicide, greenhouse and Petri dish bioassay studies based on CRD with 4 replications were conducted at Weed Research Department of Iranian Research Institute of plant Protection during 2008 and 2009. The resistance level of biotypes was determined in pot trials, while the herbicide dose required for 50% reduction of coleoptile length of the susceptible biotypes (GR50) as well as the susceptibility and resistance level of biotypes were studied in Petri dish bioassay trials. The experiments were conducted on 12 annual ryegrass biotypes collected from wheat fields of Fars province. The susceptible (FS) and 11 suspected to resistant biotypes (including ES1, ES2, ES3, ES4, ES5, M1, M2, M3, F1, FJ and FI2) were sprayed at 2- to 4-leaf stage by applying 0-32 times of recommended dose of Pinoxaden herbicide including 0. 45, 90, 180, 360, 720 and 1440 g ai ha-1 in greenhouse experiments. The germinated seeds were also exposed to 0, 0.4, 0.8, 1.6, 3.2, 6.4 and 12.8 g ai l-1 in Petri dish bioassay experiments. The percentage of dry matter and plant survival of each biotype was calculated compared to the untreated control and the resistance level was determined four weeks after herbicide application in greenhouse experiments. The percentage of coleoptile length of biotypes compared to the control was assessed 7 days after treating the germinated seeds with herbicide in Petri dish bioassays and the resistance level of biotypes were calculated. The results of greenhouse and Petri dish bioassay studies indicated that 4 biotypes including ES4, M2, F1 and FJ were resistant to Pinoxaden herbicide. As a general conclusion, most of the studied biotypes were sensitive pionoxaden.

In order to evaluate the resistance of wild oat bitypes to clodinafop-propargyle, pinoxaden and their mixture (traxos), collected from Fars and Khoozestan provinces, pot and Petri dish bioassay studies were conducted on 8 suspected to resistance wild oat biotypes as well as one susceptible biotype at Iranian Research Institute of Plant Protection during 2008-2009. In pot bioassay experiments which were conducted as RCBD with four replications, wild oat plants were sprayed during 2-4 leaves stage using 0.25-16 times the recommended dose. Based on herbicide recommended rates (0.8, 0.45 and 1.5 l/ha for clodinafop-propargyle, pinoxaden and traxos, respectively), the applied doses were 0, 16, 32, 64, 128, 256, 512 and 1024 g ai ha-1 for clodinafop-propargyle, 11.25, 22.5, 45, 90, 180, 360 and 720 g ai ha-1 for pinoxaden and 16.87, 33.75, 67.5, 135, 270,540 and 1080 g ai ha-1 for traxos. In Petri dish bioassay studies, after determination of discriminating dose for each herbicide (0.05, 0.03 and 0.01 mg ai/l for clodinafop-propargyle, pinoxaden and traxos respectively), dose response experiments using 0.25-16 times of the discriminating dose were conducted on germinated seeds. The results indicated that all biotypes was resistant to clodinafop propargyl and cross resistance to clodinafop-propargyle, pinoxaden and their mixture (traxos) in Khoozestan populations were confirmed. Greater than 37% of biotypes were controlled by pinoxaden or traxos herbicides and the resistance level of all biotypes to traxos was lower than other herbicides.

In this study the effects of osmotic potential of water and drought stress on seed germination and seedling emergence of wild mustard (Sinapis arvensis) ecotypes were studied. The seeds were collected from four provinces including Fars, West Azarbaijan, Khoozestan and Mazandaran. Trials were carried out to study the effects of osmotic potential of PEG-6000 solutions at seven levels (0, -0.01, -0.05, -0.25, -0.1, -0.5, -1.5 MPa) on seed germination of four populations of wild mustard. In addition, the seedling emergence pattern of the populations was investigated in response to three soil moisture regimes (field capacity (FC),FC–1/3FC–FC, FC–1/6FC–FC) on percent weed emergence in a greenhouse. Results showed the highest germination occurred at 0 MPa osmotic potential. Germination gradually decreased by reducing the osmotic potential to -1.5 MPa. The trend was different among the ecotypes. The most number of germinated seeds was observed at high soil moisture (field capacity). The seeds of all ecotypes were sensitive to drought stress. Seed undr drough stress transformed to secondary dormancy and hence returning to field capacity did not induce germination.