WEED RESEARCH JOURNAL
Year:2009 | Volume:1 | Issue:1|Papers Count:8

In order to determine allelopathic effects of water extract of canola residues on seed germination of redroot pigweed (Amaranthus retroflexus), wild radish (Raphanus raphanistrum) and foxtail (Alopycorus myosoreides) was investigated in 2006. A factorial experiment based on a completely randomized design with three replications was conducted. Treatments were three kinds of water extract of canola (shoot, root and shoot + root) and five concentrations (0, 25, 50, 75 and 100 percentage) of extracts. Each plot was a Petri-dish with 9 cm diameter and 3 cm depth. At the end of germination, germination inhibition, shoot / root ratio, root dry weight, root length and seedling dry weight were determined according to ISTA method. The results showed that, water extract of canola did have difference allelopathic effects on weeds seed germination. The germination percentage, shoot / root ratio, root length and seedling dry weight decreased with increasing concentration canola extract. Seed germination of wild radish then redroot pigweed and foxtail showed more sensitive to canola extract. The water extract of root then shoot and shoot + root of canola showed the most allelopathic effects on seed germination and seedling growth of weeds.

Two field trials conducted to investigate chemical and mechanical methods of weed control in canola (Brassica napus L.). Under MAKHAR (i.e. Irrigation for suitable tillage condition) and no MAKHAR conditions. Experiments with split block and 4 replications were used in Shavoor station in 2001-2003. Main plots of the two experiments were showel cultivator and non-cultivator and hand weeded. Sub plots were trifluraline herbicide (2 l/h), ethalfluralin herbicide (3 l/h) and no herbicide treatments. The results showed that the highest dry weight and the lowest of both two experiments obtained from no cultivator and no herbicide treatments, which showed significant differences. The highest yield was obtained from hand weeded plus herbicide treatment and also from cultivator plus herbicide tratment. These results showed that if herbicide is used in canola, the crop will grow rapidly as a result of weed control and approperate air flow in soil and it will over come the remaining weeds and high yield will be obtained. Either of the two herbicides (trifluraline and ethalfluralin) showed the same effect on weed control by itself during the two years of experiments, but in the second year when it associated which cultivator, trifluraline showed higher yield than ethalfluralin. The use of trifluraline and ethalfluralin by itself could not control Sinapis arvensis, Silybum marianum and Malva rotundifolia and the used of cultivator by itself could not control weeds as a result of observing weeds remaining on rows. The results of this study demonstrated that by using herbicides such as trifluraline and ethalfluralin plus cultivator we are able to control weeds. A comparison between the two experiments showed that under MAKHAR condition, the yield of canola and dry weight of weeds were higher and lower than no MAKHAR respectively. These results showed that pre-cultivation MAKHAR could decrease weed growth and consequently increases yield.

Effects of trifluralin (2, 6-dinitro-N, N-dipropyl-4-(trifluoromethyl) benzenamine) and iron on morphological characteristics and iron absorption of five cultivars of soybeans (Glycine max L. Mevr.) were studied using a completely randomized block design under greenhouse condition. Treatments consisted of five levels of trifluralin (0, 1, 2, 3, 4, mg a.i/kg soil), three levels of iron (0, 5, 10 mg a.i/kg soil), and five cultivars of soybeans (Williams, Clarck, Pershing, KW505, SRF 450). Results indicated that increase in trifluralin concentration significantly decreased plant height, stem diameter, leaf area, dry weight of shoot and root and root nodules in all cultivars for all levels of iron. However, root to shoot dry weight ratio was increased. Trifluralin at zero iron level, caused significant reduction in chlorophyll and iron concentration of shoot in Williams, Pershing and KW 505, but did not have any effect on Clarck and SRF 450. Trifluralin application at 5 and 10 mg iron/kg soil did not significantly affect chlorophyll and iron concentration. With trifluralin application, reduction rates of chlorophyll and iron concentration in cultivars were significantly different. The highest sensitivity was observed in KW505 and Pershing and the lowest in Clarck and SRF450. Application of 5 mg iron/kg soil, significantly increased leaf area of KW 505, but did not have any significant effect on trifoliate leaf number. Application of 5 and 10 mg iron /kg soil significantly increased shoot dry matter in KW 505 and Williams respectively, but root to shoot dry weight significantly decreased with application of 5 mg iron/kg soil. Application of 5 mg iron/kg soil significantly increased root dry weight of KW505. Iron application did not have any significant effect on dry matter and number of root nodules. However iron application significantly increased leaf chlorophyll concentration of Williams, Pershing and KW 505 and shoot iron concentration of all cultivars.

Present investigation carried out to study different weed control methods in spring safflower (Carthamus tinctorius) under rain fed condition. The experiment was conducted in Sararood Research Station located in west of Iran in 2006. The experimental design was a factorial based on RCBD with four replications. Factor A was included 4 different herbicides Trifluralin at 960 gr a.i./ha, Pendimethalin at 660 gr a.i./ha, Ethalfluralin at 1172.5 gr a.i./ha, Imazametabenz at 625 gr a.i./ha. and Factor B was 4 different method including without mechanical control, hand weeding at the 6 leaves stage, cultivator at 6 leaves stage, hand weeding at the 12 leaves stage + cultivator at 6 leaves stage along with two checks namely without weed, and without any weed control. The result showed that mechanical control after the herbicides application increased weed control compared with the herbicides applied alone. A cultivator at 6 leaves stage with a hand weeding at 12 leaves stage with Imazamethabenz herbicide application increased weed control compared with all other stage. Decreasing of weed dry weight was observed in integrated treatments and sole herbicides treatment had less effect on reducing of weight dry weed.

This study was carried out during 2003-2004 to investigate efficiency product of Fenoxaprop-p-ethyl for control Avena luduviciana in Fars agriculture and natural resources research center. The experiment was done under RCBD with 4 replications and 14 treatments. Treatments included Fenoxaprop-p-ethyl from Golsam company, Gia and Bayer (Germany) companies at four doses: 0.4, 0.8, 1.2 and 1.8 (l/h). Spraying was done at tillering stage of wheat. Effect of treatments were determined on decreasing percent of weed density, weed dry matter and wheat yield. Statistical analysis of the dose response data were fitted to a Log- Logistical model. Dry matter and density response of the Avena ludoviciana to the herbicides were shown well by Log- Logistical modle. The efficiency of Fenoxaprop-p-ethyl formulations from Foreign company (German) at 1.2 l/h was very good (98%). Also, efficiency of formulations from Golsam company at the highest dosage (1.8 l/h) was very good (96%), and efficiency of formulations from Gia company at the (1.8 l/h) was moderate (92%). Yield reduction in the highest dosage of Bayer company (Germany) formulation was more less than the others.

This research was conducted in 2007 to evaluate the efficacy of penoxsulan SC 240 as a new rice selective herbicide. Penoxsulam at 24, 30, 36 and 42 g ha-1 was compared with mixture of anylofus and ethoxysulfuron (Sunrise) at 945 g ha-1, tank mix application of butachlor plus cinosulfuron at 900+20 g ha-1, and butachlor plus bensulfuron at 100+45 g ha-1 for controlling barnyard grass (Echinochloa crus-galli), Cyperus difformis and rice broadleaf weeds. Efficacy of penoxsulam at 36 and 42 g ha-1 in control of E. crus-galli was the same as that of the other herbicide treatments and better than its application at 24 or 30 g ha-1. Penoxsulam at 36 or 42 g ha-1 and Sunrise were more efficient in control of C. difformis than the other treatments. In control of Alisma plantago-aquatica, penoxsulam at 36 and 42 g ha-1 had no significant difference with the other herbicides, but was significantly more efficient than its application at 24 or 30 g ha-1. Penoxsulam at 42 g ha-1 controlled Sagitaria trifolia same as Sunrise and significantly better than the other treatments. All herbicides greatly reduced the dry weight of the target weeds. The herbicides showed no any evidence of phytotoxicity on rice and had no effect on rice plant height and dry weight, compared with weedy check.

The experiment was carried at evaluate the relationship between weed seed bank at the early season of and weed population during growth season, its dispersion pattern, an experiment was done on exploratory from of Karaj agricultural school located in Mahdasht in 2007. In this experiment, sampling the seed bank at the beginning of the season and weed population during the season including sampling corn 4-leaves stage, 8-10-leaves stage and Tassel formation stage, from 96 parts was performed by using gridding method. A meaningful correlation coefficient of r=0.83 between seed bank at the beginning of season and weed seedling during growth season was observed. To study change seed bank and seedling duration season and connection between suitable pattern for to foresee composition and densities weed species in field and choosing the best date, best method for correct management for decrease seeds densities in seed bank. Distribution seeds and floor was peachiness. In addition to, the floor stage 1 indicated the most correlation with seed bank. Broadcasting models of weed species into field was patching and different patches diagonal (has) did differ among species. We can see the best time for sampling with relationship between seed and seedling then distinguish weed fighting time.

Bioassay techniques used in herbicide studies are based on the response of chosen organisms, higher plants or microorganisms, to the chemical. Various means of assessment are used: seed germination, weight or size of plant parts, modification in physiological activities such as photosynthesis and transpiration, and typical symptoms. Several special bioassays are described. Does-response relations are affected by the age of the indicator plant and environmental conditions of growth. Results can be estimated visually by objective measurements; for correct interpretation appropriate controls and standards must be included in each experiment. Examples are given of bioassay procedures developed to investigate various aspects of herbicide behavior: soil effects, dissipation from soil surface, movement in soil, degradation and persistence.