JOURNAL OF WEED ECOLOGY
Year:2013 | Volume:1 | Issue:1|Papers Count:6

In order to evaluate the phenology stages of Camelthorn (Alhagi pseudoalhagi), an experiment was carried out in 2008 in two cities, of Yazd province Yazd and Taft (Cham), in spring. By growing camelthorn, the phenology stages in both areas, from emergence time to seeding, were recorded. The results showed that 7 phenology stages of the Camelthorn took 211 days (equal to 4049 growing degree days) in Yazd, while The same Stage decreased 200 days (equal to 3503.45 growing degree days), in Cham-Taft. The shortest and the lorgest Phenology period of Camelthorn in both yazd and Cham-Taft referes to budding (22 days) and seeding (90 days), respectively. Also, the shortest distance in terms of time from starting of one stage to the next in both sites, was due to the starting growth period of Camelthorn from surface to appearance of first stem, and the longest distance in terms of time refered to starting of fruiting and seeding.

To evaluate the impacts of individual and tank-mix application of common herbicides on weed control as well as saffron corm an experiment with nine treatments and three replications was conducted in a saffron field in Neyshabour. The treatment included herbicides such as Oxyfluorfen 1.5 l. ha-1, Ioxynil 2 l. ha-1, Metribuzin 750 g. ha-1, Sethoxydim 2 l. ha-1, Fluazifop-P-Butyl 2.5 l. ha-1, Haloxyfop-R-methyl 1.3 l. ha-1, Oxyfluorfen+Haloxyfop-R-methyl, Ioxynil+Haloxyfop-R-methyl and Metribuzin+haloxyfop-R-methyl. Orthogonal comparisons showed that tank-mix application could significantly reduce weeds dry matter in comparison with individual application of their components. Compared with Ioxynil+Haloxyfob-R-metyl, tank mix application of Haloxyfop-R-methly with Oxyfluorfen or Metribuzin could significantly reduce weeds’ dry matter. Sethoxydim had the least effect on weed dry matters. The maximum weight of saffron corms were observed in treatments including Oxyfluorfen+Haloxyfop-R-methyl, Ioxynil+Haloxyfop-R-methyl, and Metribuzin+Haloxyfop-R-methyl.

In order to evaluate effects of drought and darkness on secondary dormancy of Brasica napus, a factorial experiment based on completely randomized design with 3 replications. The treatments included 7 various canola (Hyola 60, Hyola 308, Hyola 330, Hyola 401, Hyola 420, Sarigol, AA1) and 3 drought levels (control, -1.5 MP water potential and dry seed). Samples were placed inside black cover in growth chamber with 20°c for 2 weeks. Results indicated that the highest and lowest germination percent was observed in Hyola 420 and Hyola 60, respectively. The percentage of germination of varieties decreased under the different drought levels significantly. The percentage of cumulative germination in total canola varieties under -1.5 MP was more than dry seeds, considerably. In general, in addition to genotype, environmental conditions affect on secondary dormancy potential of seeds. In total varieties, except of Hyola 60, germination percent and rate was decreased, due to enviromment moisture.

In order to investigate the allelopathic effects of crocus petals on seedling growth of sorghum (Sorghum bicolor), wheat (Triticum aestivum), barnyard grass (Echinochloa crus-gali) and wild pigweed (Amaranthus retroflexus), five dilutions of 1% aquatic extract were prepared as 0, 10, 30, 60, and 100% of full strength. Five milliliters of each dilution was added to petri dishes containing 25 seeds laid between papers. After 10 days, plumule and radicle length was measured. Log-logistic model was fitted to radicle length response of sorghum, wheat and barnyard grass via extract concentrations but for wild pigweed the Gompertz model was better. Based on EC50 of radicle length, the sensitivity order of plants was pigweed, sorghum, barnyard grass and wheat. The five-parameter models including hormesis term were best suited for plumule length response of wheat and barnyard grass and pigweed to different concentrations. The hormesis phenomenon was observed for lower concentrations than 50% and dose giving maximum stimulation for wheat, barnyard grass and pigweed was 10.76, 12.33 and 14.02%, respectively. Germination percent was not affected by aqueous concentrates at the test plants except of pigweed that had been reduced significantly by the full strength of concentration.

Broomrape is one of the most troublesome parasite weeds in the tomato fields of Iran that use of fumigant material is one of the way for its control. Five application doses 0, 500, 750, 1000, 1250, 1500 l ha-1 of Metam-Sodium were applied by shank injection in a tomato filed of Astan Qods in Mashhad during 2011. The experiment was arranged in a completely randomized block design with four replications. Plots were divided in two parts so that in one half only weeds were removed and in the other one both weeds and broomrapes were maintained throughout the growing season. Densities and dry weights of broomrape as well as weed size were measured in each half part separately. The results showed that Metam-Sodium was able to reduce weed density as three-parameter logistic dose response curve. The most tolerant weeds were pigweed and common lambs-quarters with ED50 of 474 and 775 l ha-1 respectively while common purslane, black night-shade and barnyardgrass were more sensitive. Despite weed reduction, there was no harvest for tomato because of high remained weed density that is probably more than weed threshold. Broomrape was not affected by metam-sodium but corresponding tomato yield increased in linear form. A decrease of soil respiration by Metam–sodium was expressed by the four-parameter Gompertze equation.

In order to identify and determine weeds distribution in rainfed wheat fields of Kermanshah province, 58 fields in 7 counties were investgated during 2001 and 2009. After weed survey the charsterictics of weed species were evaluated. Then density, frequency, uniformity, mean density, abundance index, Shannon- Weaver diversity index and Simpson index were determined. In rainfed wheat fields of Kermakshah province 91 weed species were identified out of which 15 species belong to grass weed and 53 species belong to broadleaf weed. Poaceae, Fabaceae, Asteraceae and Rubiaceae were the most important families with, 57, 35.5, 34.6 and 18 percent of FIV, respectively. Based on the result of this study Galium tricornatum, Vicia hyrcanica, Vaccaria pyramidata and Anthemis cotula were the dominant broadleaved weeds. Avena ludoviciana, Hordeum spontaneum and Bromus tectorum were the most important grass weeds. In addition the most important troubeling preharvest weeds were Convolvulus arvensis, Carthamus oxyacanthus and Glycyrrhiza glabra in rainfed wheat fields. Shannon-Weaver diversity index showed the highest species diversity were in Kermanshah with 2.67 and the lowest species diversity in Songhor and Sarpolezohab were with 1.8 and 1.9, respectively.