To evaluate the effect of nitrogen and water withholding in vegetative growth stage of corn on efficacy of nicosulfuron and 2,4-D+ MCPA an experiment was conducted as a factorial arrangement in a randomized complete block design with three replications at Tarbiat Modares University in 2017. The first factor contained four treatments including application of nicosulfuron, 2,4-D+ MCPA, weed free and weed infested as control. The second factor consisted of normal irrigation and water withholding from 4 to 8 leaf stage. Third factor contained either urea application or no fertilizer application. Normal irrigation and nitrogen fertilizer application significantly increased nicosulfuron and 2,4-D+ MCPA efficacy in weed control and total weed dry weight decreased to 341 and 361 g.m-2 respectively compared 1370 g.m-2 as weed infested. Nicosulfuron and 2,4-D+ MCPA reduced weed total dry weight significantly under irrigation withholding. Grain yield increased with application of nitrogen and nicosulfuron. Grain yield was higher with application of 2,4-D+ MCPA than nicosulfuron without nitrogen application under irrigation withholding. Application of nicosulfuron with nitrogen application provided satisfactory weed control and increased grain yield.

In order to study of crop rotation and weed management methods effects on weed population, a 5-yr experiment was conducted from 1384 at field research of plant protection research institute, Karaj, Iran. The experimental treatments were crop rotation (including: sugar beet-sugar beet and sugar beet-wheat) and weed management method (including: chemical, chemical+ mechanical and hand weeding) that arranged in factorial experiments based a randomized complete block design with 4 replications. In contrast with sugar beet- wheat treatment, results indicated that annual and perennial weed populations increased in the end of rotational period in mono-culture system. Annual weed population also decreased in integrated weed management plots but it had no effect on perennials. Result suggested that the weed seed community in a sugar beet- wheat rotational system differs in structure and composition from communities associated with continuous sugar beet system, which in the end of 5 years experiment, percentage of bindweed and Johnson grass seeds in soil(in compare with knotweed and amaranth) were fewer in rotational treatments and they distributed in layers deeper than in 0-10 (cm) layer of soil.

Introduction Several factors affect the crop yield and weeds are among the most important factors reducing crop yields. There are high tendency to develop alternative methods of herbicides for natural control of weeds in organic products. One of the alternative methods to manage weeds is intercropping. Intercropping is growing two or more crops simultaneously in a piece of land during a growing season. The objectives of the present study were to examine the effect of cereal-legume intercropping on weeds growth. Materials and Methods A field experiment was conducted in College of Agriculture of Darab, Shiraz University during 2014-2015. In the experiment 16 treatments (five weed free monocultures of wheat (M1), barley (M2), triticale (M3), pea (M4), faba bean (M5), 5 weedy monocultures of wheat (WM1), barley (WM2), triticale (WM3), pea (WM4), faba bean (WM5), and six replacement intercropping treatments of wheat + pea (I1), wheat + faba bean (I2), barley + pea (I3), barley + faba bean (I4), triticale + pea (I5) and triticale + faba bean (I6) without weed control) using a randomized complete block design (RCBD) with three replicates were studied. Cereals and legumes were planted simultaneously at 23 November 2014. Planting operation was conducted on both sides of the ridges. weed diversity was calculated by Shannon diversity index: 1 ln s i H N i N i  N N    N=Total number of plants in each plot of one square meter, Ni= number of species i plants, S= total number of species, and H= Shannon diversity index. This index value ranging from zero to five, higher index value, greater diversity. Results and Discussion The results showed that the lowest density and biomass of weeds were obtained in both sole culture and intercropping of barley. For instance, the lowest weed biomass was observed in monoculture of weedy barley (1 g. m-2), intercropping of barley + faba bean (12. 67 g. m-2) and intercropping of barley + pea (56 g. m-2). The weed density at weed free sole culture of barley (30 plants. m-2) was lowest that followed by barley + faba bean intercropping (81 plants per m-2). The lowest species weed diversity was obtained in barley + pea (zero) and weedy barley (0. 007), respectively. The weed diversity of most intercropping treatments was similar or less than that of weedy sole culture. In General, pea or faba bean monoculture had greatest weeds density and biomass, because slow growth and late seedling establishment. However, cereals especially barley controlled weeds properly, due to greater growth rate, higher height and greater density than those of legumes. Intercropping of pea and faba bean with cereals reduced weeds growth and had lower weeds density and biomass than those of pea and faba bean weedy monocultures. In order to increase of legume yields, more density of legume should be intercropped with cereals. Conclusion In general, intercropping treatments caused a significant decrease in weeds density and biomass compared to the legumes monoculture. In this experiment barley and triticale due to good properties such as fast growth, high plant height and more shading could considerably control weeds in both monoculture and intercropping treatments, reducing significantly weeds density and biomass in itself sole culture and intercropping treatments. To reduce the weeds growth in faba bean and pea, which have a poor competitive ability with weeds, intercropping with cereals, especially barley and triticale, in the south of Fars province is recommended. However, intercropping is one of the ways to reduce weeds in the long term and its effects on weeds in the long period will be much more. Acknowledgments The authors would like to acknowledge the College of Agriculture and Natural Resources of Darab, Shiraz University, to finance the project and all those who helped us in this project.

A field experiment was undertaken to determine optimum combination of weed management practices and inter-row spacing levels for effective weed control in maize at Bako agricultural research center, Western Oromia, Ethiopia during 2018 main cropping season. The treatments included pre-emergence s-metolachlor 290 g/L + atrazine 370 g/L (1.0, 2.0 and 3.0 L ha-1), hand pulling and hoeing 25 and 45 days after sowing (DAS) and weedy check in combination with inter-row spacing levels (65, 70, 75, and 80 cm). The experiment was laid out in a randomized complete block design with a factorial arrangement in three replications. The experimental field was infested with 22 weed species belonging to 12 families, out of which 77.3 %, 18.2 % and 4.5 % were broad leaved, grass and sedges, respectively. weed management practices (WMP), inter-row spacing (IRS) and their interaction significantly influenced the weed density, dry weight and weed control efficiency at 25 and 70 DAS. All parameters of the crop were significantly affected by WMP and IRS. However, their interaction was non-significant except for number of ear per plant and grain yield. The highest grain yield was recorded in inter-row spacing of 65 cm treated with hand pulling and hoeing 25 and 45 DAS (10492.0 kg ha-1). Whereas, the lowest grain yield (2237.0 kg ha-1) was obtained from weedy check plot at 80 cm inter-row spacing. On the other hand, maize planted at 65 cm IRS in combination with 2 L ha-1 s-metolachlor 290g/L + atrazine 370 g/L gave comparable grain yield which was statistically at par with that of hand pulling and hoeing 25 and 45 DAS and 3 L ha-1 s-metolachlor 290g/l. + atrazine 370 g/L involving the same IRS. Hence, putting the environmental concern and scarce labor force under consideration, the use of reduced rate (2 L ha-1) of herbicide in combination with narrower IRS would be the best option for effective weed management in maize. Furthermore, integration of narrower IRS with other weed management treatments enhance maize grain yield there by improving weed control efficiency.

In order to study and compare chemical and non-chemical methods of weed management in saffron (Crocus sativus) fields, two field experiments were carried out in a randomized completely block design with three replications at Research Field Station of Gonabad during 2009 to 2011. Treatments included cover crops of barely, Mushroom bed mulch, herbicides of haloxyfop R methyl ester (EC10%), iodosulfuron methyl sodium+mesosulfuron. methyl+mefenpyr. diethy (WG6%) l, hand weeding (DF75%) and control. For determining the ability of treatments for weed control, dry matter of weed, leaf dry weight of saffron, stigma and saffron flower yields were determined. Results showed that dominant weed species were mouse barely (Hordeum murinum), wild barley (Hordeum spontaneum) Hoary cress (Cardaria draba), and yarrow (Achillea millefolium). Herbicides of iodosulfuron methyl sodium+mesosulfuron methyl+mefen pyr. Diethy (WG6%) destroyed grasses and broadleaf, but it destroyed saffron plant too. Haloxyfop. R methyl ester damaged grasses but decreased stigma yield and leaf of saffron. Applied mulch was not be able to control the weeds, however, it increased saffron stigma yield. Cover crops of barley significantly decreased weed dry matter weights. Barley caused least weeds dry matter weight similar to hand weeding. In conclusion, the treatments of cover crops showed the best performances in weed control and saffron yield comparing to other studied weed management methods.