IRANIAN JOURNAL OF WEED SCIENCE
Year:2012 | Volume:8 | Issue:2|Papers Count:8

In order to investigate weed control in sesame farms, a two-year experiment with Randomized Complete Blocks Design, 10 treatments and 3 replications was carried out in Jiroft and Kahnuj during 2006-2008. Treatments included trifluralin 48% EC at 2.5 L/ha (pre plant incorporated) +haloxyfop ethoxy ethyl 12.5% EC at 2 L/ha. post emergence of grassy weeds, alachlor 48% EC at 5 lit/ha pre-emergence, oxyfluorfen 24% EC at 2 lit/ha postemergence, pendimethalin 33% EC at 4 lit/ha pre-emergence, above treatments+one hand weeding, two hand weedings and weed free check. Results indicated that all treatments reduced weed density and dry weight. Trifluralin and alachlor reduced Dactyloctenium aegyptica dry weight by 63 and 56% respectively. Alachlor and pendimethalin reduced Digera muricata dry weight by 94 and 91% respectively. The latter treatments also increased sesame yield by 75 and 65% respectively.

In order to evaluate weed control in seedling alfalfa, an experiment was conducted at the Agricultural Research Center of Jiroft in a randomized complete blocks design with 3 replications and 8 treatments for two years.Treatments included Imazethapyr %10 SL at 0.5, 0/75 and 1 Lit/ha+Cytogate at 1Lit/ha in 10-15 cm alfalfa, post emergence of weeds+Cycloxydim %10 EC at 2 Lit/ha post emergence of grass weeds, Pendimethalin %33 EC at 2 and 3 Lit/ha (pre- emergence), Chlorthal-dimethyl %75 WP at 6 and 8 kg/ha+Cycloxydim at 2 Lit/ha, weed free check. The results showed that Chlorthal-dimethyl and Pendimethalin controlled Malva parviflora better than Imazethapyr, and Imazethapyr controlled Brassica tourenforti better than Chlorthal-dimethyl and Pendimethalin. All herbicides showed similar efficiency on Chenopodium and Digera muricata control. Imazethapyr was the best herbicide of the experiment and at 0.5 and 0.75 Lit/ha produced the highest alfalfa biomass in the first and second harvests. Chlorthal-dimethyl increased alfalfa biomass at second harvest, but Pendimethalin caused phytotoxocity on alfalfa and reduced its biomass.

In order to determine the critical period of weed control in Thyme (Thymus vulgaris), an experiment was carried out in a randomized complete blocks design with 18 treatments and three replications in 2008-2009 at the research field of the medicinal plants departments, Shahed University, Tehran, Iran. Two series of the treatments including weedfree and weed-infested were applied in the regular time distances of 15, 30, 45, 60, 75, 90, 105 and 120 days right after the beginning of thyme growth at spring. Two check treatments including full and no control of weed during the whole season were also included. The nonlinear models kind of logistic and Weibull were applied to determine the start and end of critical period of weed control respectively. Major weed species were field bindweed (Convolvulus arvensis), flixweed (Descurainia sophia), mon groundsel (Senecio vulgaris) and prickly lettuce (Lactuca scariola) with greater biomass and size. The results showed that periods of weed- free and weed- infested significantly affected the dry weight and number of weeds in all treatments. Considering 5% and 10% of the acceptable yield loss in the models, critical periods of weed control were between 41-90 days and 54-76 days for fresh weight, 12-94 days and 29-78 days for dry weights, and 20-105 days and 30-86 days for essence yield after the beginning of growth at spring.

Swallow-wort (Cynanchum acutum) is a problematic weed which has recently infested many agricultural fields in Iran especially orchards. Therefore, a three-year experiment was conducted in a randomized complete blocks design with 3 replications in a pistachio orchard in Yazd. Treatments included post-emergence herbicides glyphosate (Roundup 41% SL) at 2, 4, and 6 L/ha+ammonium sulphate (8 kg/ha), paraquqt (Gramaxon 20% SL) at 3 L/ha, garlon (Triclopyr 62% EC) at 2 L/ha, cutting of swallowort, and weed infested control. Results of the first year showed that the best treatment for the control of swallowort was 3 times spraying with glyphosate 6 L/ha. In the second year, the best treatment for the control of swallowort was 3 times spraying with glyphosate 6 L/ha or 3 times spraying with Triclopyr 2 L/ha. Based on the results of the third year, the best treatments for the control of swallowort were 3 times spraying with glyphosate 6 L/ha, 2 and 3 times spraying with triclopyr 2 L/ha or 2 times cutting+triclopyr 2 L/ha. Therefore, it seemed that the systemic herbicides glyphosate and triclopyr had more efficiency in the control of swallow wort, compared to the contact herbicide paraquat.

Chemical and mechanical control of Cynanchum acutum (CA) in pistachio orchards of Kerman was investigated during 2007-2010. The experiment was performed in randomized complete blocks design with 4 replications and the following 22 treatments: glyphosate (41% SL) at 6 L/ha+8 kg ammonium sulfate, 1, 2 and 3 times, paraquat (20% SL) at 3 L/ha, 1, 2 and 3 times, glufosinate-ammonium (Basta, 20% SL) at 5 L/ha, 1, 2 and 3 times, triclopyr (Garlon, 62%) at 2 L/ha, 1, 2 and 3 times, nicosulfuron (Cruz, 4% SC) at 2 L/ha, nicosulfuron at 2 L/ha+glyphosate (41% SL) at 6 L/ha+8 kg ammonium sulfate, nicosulfuron at 2 L/ha+paraquat at 3 L/ha, glyphosate (Weed Master, 36% SC) at 2 and 3 L/ha, 1 and 2 times, mechanical surface cutting, 1, 2 and 3 times. All treatments were carried on C. acutum at 10 cm growth stage. After every treatment density of CA was determined and compared to the density at the beginning of the experiment, as percentage. Results indicated that all treatments succeeded in reduction of CA density. The most effective treatments included glyphosate (41% SL) at 6 L/ha+8 kg ammonium sulfate, or glyphosate (Weed Master) at 2 L/ha, with one or two repetitions as needed. Surface cutting was also effective as a non chemical means.

To investigate the effect of planting time of cover crops on corn-weed interaction, an experiment based on randomized complete blocks design with three replications was conducted in Sari Agricultural Sciences and Natural Resources University during growth season of 2010. Treatments consisted of three cover crops (soybean (Glycine max L.), fenugreek (Trigonella foenum gracum L.) and cowpea (Vigna unguiculata L.)) in two different planting dates (simultaneous with corn and 21 days after planting of corn), along with two controls (no weeding and weeding). Results showed planting the cover crops soybean, fenugreek and cowpea in the first and second dates reduced by 96, 93, 83, 68, 91 and 97 percent of weeds biomass. Also, these cover crops reduced was density by 90, 85, 64, 52, 81 and 90 percent and weed density, 73, 62, 51, 17, 62 and 80 percent, in all three samplings compared to treatments without weeding, respectively. The lowest yield of corn grain was 5246/1 Kgh-1 in plots with no weeding and the highest was 11853/13 and 11447/4 Kgh-1 in plots with complete weeding and cowpea in the second date of planting, respectively. The results of this research showed that use of leguminous cover crops with suitable management is a good weed management system which increases efficiency of input and brings us closer to sustainable agriculture.

To investigate effect of the amount and the methods of nitrogen and phosphorus application on weed management of wheat, an experiment was performed as factorial, based on randomised complete blocks design with three replications at the Research Farm, Faculty of Agriculture, Ferdowsi University of Mashhad, Iran during 2009.Treatments included nitrogen at (100, 200, and 300 kg ha-1 phosphorus at 100, and 200 kg ha-1 and their application methods (Broadcast and Band application). Phosphorus source for fertilization was triple superphosphate applied soil incorporated before wheat sowing and N2 source was urea: 50% applied pre plant and 50% at shooting stage.The results showed that fertilizer application methods significantly affected wheat yield and weed biomass and density (p£0.01). Phosphorus and nitrogen band application method reduced weed biomass and weed density by 54% and 34% respectively and increased wheat biomass and seed yield by 21% and 36% compared to broadcast application method. The interaction effects of nitrogen and phosphorus application rate and also the interaction of phosphorus and nitrogen application methods showed that the fertilizer band application × 200 kg ha-1 phosphorus rate and 300 kg ha-1 nitrogen rate were the best treatment in wheat yield improvement and reducing weeds. These results indicated that by modifying fertilizer application methods and changing the amounts of their application, we may improve fertilizer use efficiency and weed management in wheat.

In order to study the effects of several weed control methods on yield and yield components of rice, a field experiment was carried out in Babol city- during 2011. The experiment was on the basis of randomized complete blocks design with 3 replications and 7 treatments including hand weeding twice, powered weeding twice, powered weeding+hand weeding, conoweeder weeding twice, herbicide application+hand weeding, weedy check and herbicide application only were used. Results showed that there was significant difference among treatments on grain yield, grain number per panicle, filled grain number per panicle, unfilled grain number per panicle, fertile tillers, panicle number, biological yield, density and dry weight of weed. In general herbicide application+hand weeding produced highest grain yield, while weedy check with high unfilled grains per panicle, less panicle number, and highest density and dry weight of weed had less grain yield. Among the mentioned traits, fertile tillers and panicle number had the highest correlation with grain yield. Unfilled grain number per panicle, density and dry weight of weed, had negative and significant correlation with grain yield.