نشریه دانش علفهای هرز
سال یازدهم شماره 2 (پاییز و زمستان 1394)

Due to its favorable weather conditions, west Azarbayejan province is the second-largest producer of sugar beet in Iran. Weeds, especially field dodder, is one of the most important components that has negative effects on the quality and quantity of sugarbeet. In order to evaluate the effect of field dodder on the photosynthetic pigments and yield (quality and quantity) of sugar beet, a study using paired t-test was carried out on four farms in Urmieh-West Azarbayejan, during 2014. Studied farms had similar date of planting (first ten days of April), uniform density (8 plants per square meter) and same cultivar (Ecbatan). In this research, 30 healthy plants and 30 plants infected with field dodder were selected from each farm. Physiological and tecnicall characteristics were evaluated at the established plant stage (8-12 leaves) and at the harvest stage of sugerbeet Results showed that dodder affected efficiency of photosynthesis on sugarbeet leaves, such that it reduced chlorophylls a and b and total chlorophyll by 30,18, and 38% respectively, but the amount of carotene was not affected. It also reduced yield by 25%, root sugar content by 108%, impure sugar by 18.5% and foliage dry weight by 18%. Dodder also increased root nitrogen content by 37.3%, but had no effect on potassium content.

Water availability effect on seed emergence of wild wheat and wild barley grass weeds in comparison to wheat was evaluated in a randomized complete block design by 4 replications in Agricultural and Natural Resources Research Center of Lorestan in autumn of 2013. Different levels of irrigation and species seed kinds were allocated to main plots, and subplots respectively. The water requirement for emergence initiation of intact seeds of wild wheat and wild barley was 73.8% and 51.1% higher than that for wheat, respectively. Maximum emergence % of intact seeds of wild wheat became 1.9, 3.8, and 6.2 times, and wild barley 1.68, 2.01 and 3.25 times as much by increasing of water availability from 12.5 mm to 15, 17.5 and 20 mm, respectively. Results show that the high percent of wild wheat and wild barley seeds (>75%) will emerge if the water requirement to be made available, that is prepare the way to management of this weeds.

Field dodder (C. campestris), as an obligate stem parasite, damages sugar beet fields of west Azarbaijan province severely. In this research, we evaluated germination indices and parasitic effects of field dodder on sugar beet yield under laboratory, greenhouse and field conditions in West Azarbaijan Agricultural and Natural Resources Research Center during 2014. Results showed that maximum germination percent (73 to 76 %) occurred at 25-30 ºC. By increasing the planting distance from 5 to 15 cm between sugar beet and dodder plants, dry weight of dodder reduced by 63% and root weight of sugar beet increased by 31.4 %. The dry shoot weight of sugar beets that were surrounded with dodder whitin 5, 10, and 15 cm distance as compared to sugar beet that were surrounded with no dodder (control) reduced by 38, 29, and 12.3%, respectively. Results also showed that field dodder life cycle, from seed to seed needed 716.9 growth degree-days. Finally, the flowering (473growth degree-days) and germination (95growth degree-days) periods were identified as the longest and lowest growing stage respectively.

An experiment to investigate wheat and wild barely phenology was conducted during 2008-2009 in the field of Plant Protection Research Institute in Varamin. Wild barely and wheat (Variety Kavier) were planted in the vicinity of each other in a randomized complete blocks design with four replications. Phenological stages based on international Zadoks scale and GDD based on growing degree days were calculated for each stage of growth. Results showed that wild barely finished its phenological stages faster than wheat. Thus, complete life cycle of wild barely required 1839/1 growing degree days and 204 days, while wheat needed 2143/1 growing degree days and 219 days. At wheat maturity seeds stage, wild barely seeds had completely fallen except for the final seed clusters. Wild barely seed dormancy period was about 45 days. Comparative study of phonological stages of wild barely and wheat showed that the plants grew together of early stages, of growth up to early tillering, from then to the end of tillering, wild barely surpassed wheat. However, in the stem elongation stage wheat surpassed wild barely. However wild barely started inflorescenc emergence sooner than wheat. Our results suppots the idea that success of wild barely to infest wheat fields is due to rapidly reaching full maturity and short seed dormancy period.

To evaluate the effect of different planting patterns on weed control in corn, an a RCBD experiment with 4 replications carried out at Karaj in RCBD with 4 replications in Karaj, Iran in 2011. Experimental treatments included: Ridge planting (band spraying; once cultivator in 45 cm corn height; twice cultivators in 25 & 45 cm corn height; hand weeding; weedy check) and bed planting (full spraying; band spraying; replacing ridge by furrow in 25 cm corn height stage; hand weeding; weedy check). The results showed that the efficiency of mechanical treatments (twice cultivators and replacing ridge by furrow) in reducing of to reduce the density of Jimsonweed (Datura stramonium) and Lambsquaters (Chenopodium album) and dry weight of lambsquaters was more than of the band spraying and full spraying treatments. Among ridge planting treatments, ridge planting twice cultivators and among bed planting treatments, bed planting full spraying were the best treatments to control of barnyardgrass (Echinochloa crus-galli) and Johnsongrass (Sorghum halepense). In general, ridge planting twice cultivators were the best treatment to control of the grass and broadleaf weeds. Grain yields obtained from bed planting replacing ridge by furrow were the same with similar to bed planting full spraying and ridge planting band spraying treatments. Among the non-chemical control methods, bed planting replacing ridge by furrow and ridge planting twice cultivators had the highest yield respectively. Also, Besides maize biological yield was similar in bed planting replacing ridge by furrow treatment with hand weeding, as well as and also biological yield of ridge planting twice cultivators with were similar to chemical control treatments. Totally, it seems that by choosing the right approperate tools in mechanical control methods (like ridge planting and twice cultivators or bed planting and replacing ridge by furrow) while managing the weeds, weed management, can could be effective step towards in production healthy crops.

Considering the effect of tillage on seed density and distribution, predicting wild oat germination in various soil depths, as affected by plowing system, is necessary. An experiment was designed to count number of wild oat seeds in soil samples taken from four depts in two occasions: first-pre spring plowing (soil surface, 0-5cm, 5-10 cm, 10-15 cm), and 15-20 cm). and second post spring plowing ( 0-5 cm, 5-10cm, 10-15). The experiment was run as randomized complete blocks design with 4 treatments (soil depths), 4 blocks (farms), and 5 replications (observations). Results indicated that pri-plowing, surface seeds had the lowest germination rate of 35%. Number of seeds reduced of depth 0-5 cm. viable seeds in pre-plowing were 81% which was significantly lower than the post-plowing 96%. It was also shown that number of seeds increased by 28% in post-plowing samples, but germination was low due to dormancy.

Pondweed is a waterlogging habitat weed of paddy fields margin which has recently invaded rice fields. Because barnyardgrass is the most abundant and important weed of paddy fields in Iran, hence adopting any program for pondweed chemical control should involve barnyardgrass control as well. Therefore, two separate trials were carried out to evaluate the efficiency of selective rice herbicides for managing both pondweed and barnyardgrass. In this experiment the treatments included applying thiobencarb (2500 g.ai.ha-1), butachlor (1800 g.ai.ha-1), oxadiargyl (105 g.ai.ha-1), pretilachlor (1000 g.ai.ha-1), bensulfuron-methyl (45 g.ai.ha-1), cinosulforun (45 g.ai.ha-1) and metsulfuronmethyl (10 g.ai.ha-1). In the first trial, each herbicide was applied separately. In the second trial herbicides were mized. Results showed that thiobencarb, butachlor and pretilachlor were effective on barnyardgrass control (≤95%) but had no effect on pondweed. Oxadiargyl was more effective on barnyardgrass (75-90%) than pondweed (35-45%). Sulfonylurea herbicides showed very good efficacy on pondweed control (≤95%) while low effect on barnyardgrass (≥35%). The second experiment was carried out in order to investigate the mixture compatibility of the two groups of herbicides with different weed control spectrum. Data of the second trial confirmed the results of the first trial and revealed that mixing the recommended dose of herbicides controlled both weeds by 95%.