IRANIAN JOURNAL OF WEED SCIENCE
Year:2019 | Volume:15 | Issue:1 |Papers Count:10

To evaluate the effect of different levels of nitrogen fertilizer and rimsulfuron herbicide interactions on weeds density and biomass and potato yield, a field study was conducted as a factorial experiment on the randomized complete block design with 3 replications in South Kerman Agriculture and Natural Resources Research and Education Center, Jiroft. The treatments included rimsulfuron 25% DF application at five levels (0, 30, 40, 50 and 60 g ha-1) and nitrogen fertilizer as urea 46 at 4 levels (0, 90, 180 and 270 k g ha-1). Weed densities was measured 30 days after spraying and weed biomass and potato yield were measured at the end of the growing season. The results showed that rimsulfuron and nitrogen fertilizer had significant effect s on density and biomass of all weeds (Digera muricata (L. ) Mart., Echinochloa colonum L., Chenopodium murale L., Malva parviflora L. and Portulaca oleracea L. ). Weed density and biomass decreased significantly, when rimsulfuron increased. In the absence of rimsulfuron, using the nitrogen increased weed density and dry weight. However, application of nitrogen fertilizer and imsulfuron increased weed control efficiency. Application of 50 and 60 g ha-1 rimsulfuron plus 180 kg ha-1 nitrogen was the best treatment for reducing the density and biomass of weeds and increasing yield of potato by 91 (35. 9 T ha-1) and 92% (36. 38 T ha-1), compared to the control treatment, respectively.

Monochoria vaginalis is an invasive weed of paddy rice fields and now has infested tens of thousands of hectares of rice fields in north, three decades after being reported for the first time in Iran. Late emergence, fast growing under rice canopy, flood tolerance and completion of life cycle after rice harvesting, allows monochoria to survive and escape from the common weed management practices in paddy rice. The efficacy of some herbicides for chemical control of monochoria in pot and field conditions were investigated in Rice Research Institute of Iran in 2017. The results of pot experiment showed that early post application (2-3 leaf stage) of soil applied herbicides including flucetosulfuron, pyrazosulfuron, benzobicyclon, pyrazosulfuron + quinclorac, triafamone + ethoxysulfuron controlled monochoria effectively (≥ 90%). Other herbicides including ipfencarbazone, thiobencarb, pendimethalin, pretilachlor, oxadiargyl and pyrazosulfuron (WG 75%) with 55% reduction in monochoria biomass were not satisfactorily effective. In the field experiment, foliar application of 2, 4-D, dicamba + 2, 4-D, bispyribacsodium, pyribenzoxim and triafamone + ethoxysulfuron reduced monochoria biomass 90% While propanil with 23% control had a poor performance in controlling of his weed.

To evaluate the effect of dust on the growth and physiological properties of wild mustard (Sinapis arvensis) and wild barley (Hordeum spontaneum), a greenhouse experiment was conducted in the Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran during 2016 and 2017. The experiment was repeated twice in the same greenhouse condition with eight weeks' interval. The pots were arranged in a completely randomized design with four replications. Analysis of variance was done as factorial split in time. The factorial combination of two weeds species (wild mustard and wild barley), and three dust concentrations (0, 750 and 1500 μ g m-3) were as the main factors, and four harvest times (8 leaves (BBCH-18), beginning of stem elongation (BBCH-30), beginning of flowering (BBCH-61) and beginning of fruit developing (BBCH-71)) were as the sub-factors. Results indicated that total fresh and dry weights were reduced with increasing the amount of dust. At the BBCH-71 growth stage, 750 and 1500 μ g m-3 dust concentrations reduced the total dry weight of both species up to 30 and 48%, respectively. 1500 μ g m-3 dust concentration decreased both photosynthesis and transpiration rates by approximately 50%.

Field weed identifications is considered as the most important step in weed management in crops. Weed numbers for each genus and species were counted. Based on the cultivated area and the area of the farms in Eshtehard county, weed population indices were calculated using weed numbers in each area at the sampling points. In each area, latitude and longitude, and altitude from the sea level, and the place of measurements were recorded by the GPS device. Results showed that there are 47 weed species in Eshtehard. The most abundant species of weeds in this county were: Syrian beancaper (Zygophyllum eurypterum), wild barley (Hordeum murinum), camel thorn (Alhagi camelorum), Black bindweed (Convolvulus leiocalycinus Boiss. ), Russian thistle (Salsola dendrioides), common lambsquarter (Chenopodium album), woodsorrel (Rumex vesicarius L), bermudagrass (Cynodon dactylon), barley grass (Hordeum spontaneum), respectively. In addition, the most important weeds of the Eshtehard county are wimmer ryegrass (Lolium rigidum), prickly lettuce (Scariola orientalis), russian knapweed (Acroptilon repens), corn cockle (Vaccaria grandiflora), common yarrow (Achillea wilhelmsii), sophora (Sophora alopecuroides), burdock (Xanthium strumarium) and other weeds with a lower frequency. The most noticeable point in this experiment was the increase in the prevalence of weed and goatmeat (11 and 9%) over the past five years, which gives rise to the concern that, due to the climatic conditions and soil and soil conditions, these two weeds are prone to become the dominant weed of the region. New species of creeping thistle (Circium arvense), swallow wort (Cynanchum acutum) and prickly lettuce (Lactuca scariola), could be a serious threat to the county farms, which could further expand to adjacent areas, although found at low densities.

In order to study of integrated management effect of weeds on yield and yield components of corn was carried out an experiment as factorial split in the base of randomized complete blocks design in three replications in 2012-2013 in Khosf, Iran. Main plots were in 2 levels (with and without cultivator) and sub plots were a combination of factors of density in 2 levels (100, 000 and 150, 000 plants. ha-1) and reduced rates of Lumax herbicide in 4 levels (0, 1. 5, 3 and 4. 5 L. ha-1 that is recommended dose). The means comparison showed that cultivation could alone decrease 67 and 71% of dry weight and the total number of weeds, respectively. Also, treatments of cultivation and 1. 5, 3 and 4. 5 L. ha-1 of herbicide application placed in a statistical group for seed yield and cultivation and 1. 5 L. ha-1 of herbicide application treatment with grain yield of 3988 Kg, caused an increase of 64. 6 and 53. 7% in grain yield as comparison with treatments of without cultivation and 1. 5 L. ha-1 of herbicide application and cultivation and no application of herbicide, respectively. Moreover, increase in plant density didn’ t have effect on grain yield. Therefore, with the aim of sustainable agriculture and reduction of chemical use in cropping systems with weed integrated management, the use dose of Lumax new herbicide can be reduced to 66% that in this case, undesirable effects of herbicides on environment and resistance of weeds to herbicides will be decreased.

In the recent years, false jagged-chickweed (Lepyrodiclis holosteoides) has become one of the most problematic broadleaf weeds in wheat and canola fields of temperate and cold regions of Iran. Due to the the importance of the time of emergence of seedlings in the success of weed competition in crop ecosystems and consequently, the use of effective weed management methods, a series of studies were conducted in the fields of Karaj and in the Weed Research Department of Iranian Institute of Plant Protection (Tehran) during 2013-2016 to determine the biological aspects of dormancy and germination of this invasive weed seeds. Results showed that there is polymorphism in seed dormancy of false jagged-chickweed. Dormancy of false jagged-chickweed seeds can be classified in the physiological category (which is related to the presence of chemical inhibitors inside the seed and the hormonal balance between Abscisic acid and Gibberellic acid). Also, seeds of false jagged-chickweed are very photo sensitive in the germination process. The results showed that first date of the emergence of false jagged-chickweed occurred in the second half of November and seed vigor of this weed reduced significantly by increasing of seeds longevity. Lepyrodiclis seedlings emerged in form of multiple flashes during autumn and winter, however more than 85 percent of total emerged seedlings appeared after receiving 552 GDD over the period of December 12th to January 12th.

To study the competition effects of annual ground cherry (Physalis divaricata) on maize yield under different rates of N fertilizer, a field experiment was conducted in 2017 in Kermanshah Agricultural and Natural Resources Research and Education Center, Kermanshah, Iran. The experimental design was a randomized complete block with factorial arrangement with three replications. Treatments included nitrogen fertilizer (50%, 100% and 150% recommended rates) and annual ground cherry density (0, 8 and 16 plants/m2). Results showed that the highest and lowest grain yield were 9929 and 6143 kg h-1 respectively that were belonged to weed free with 150% recommended N and 16 plant annual ground cherry/m2 with 50% recommended N, respectively. High densities of annual ground cherry reduced grain yield, grains per row, row number per ear and 1000 kernel weight. Different N rates caused significant variations in grain yield and some of the yield components of maize and annual ground cherry properties like dry weight and height. Overall, results indicated that in fields, where annual ground cherry is the dominant, increasing N application rate to 150% recommended rate, increased maze yield by 17. 02.

To evaluate the effect integrated application of mulch with reduced doses of imazethapyr on weeds in bean, a factorial experiment was conducted based on randomized complete block design with three replications and 16 treatments in Tabriz in 2015. The first factor was much application with four levels including straw mulch, living mulch, no mulch and one hand weeding and the second factor was different doses of imazethapyr including 0, 50, 75 and 100 % of recommended dose (100 g ai. ha-1). Results indicated that the interaction effects of herbicide dose and mulch application was significant on weed biomass, plant height, leaf area index and grain yield of bean. The lowest weed biomass was observed in hand weeding +100 % imazethapyr (106. 5 g. m-2) that was not significantly different from straw mulch+100 % imazethapyr and living mulch +100 % imazethapyr. In 100 % dose of imazethapyr treatment, the living and straw mulch significantly increased the leaf area index of bean compared to 100 % imazethapyr. The hand weeding + 100 % imazethapyr treatment produced the highest bean grain yield (78% of weed free) and the straw mulch + 100 % imazethapyr (64% of weed free) and living mulch+ 100 % imazethapyr (53% of weed free) were the next. Generally, it could be concluded that post-emergence application of imazethapyr had low efficacy in bean weed management and using non-chemical treatments such as much and hand weeding could increase the weed control efficacy in this crop.

Wild barley (Hordeum spontaneum C. Koch) population dynamic in a wheat-chick pea-wheat rotation was investigated in a randomized complete block design by split-factorial arrangement with three replications in Great region of Khorramabad, Iran, 2009-2011. Wild barley pick ing to prevent current year seed rain in wheat and chick pea sowing time in the next season were main plots and weed management treatments in chick pea were sub-plots. In spring 2009, a Wheat field with relatively uniform wild barley infestation to was chosen. The experiment included three factors: (a) wild barley weed seed rain in wheat at two levels: 1-without seed rain, 2-seed rain; (b) chick pea sowing time at two levels: 1-early planting, 2-late planting; and (c) 5 levels of weed management in chick pea: 1-hand weeding, 2-post-emergence application of clethodim, 3-preemergence application of metribuzine, 4-pre-emergence application of imazethapyr, and 5-weedy check. In autumn 2010, wheat was planted in experimental plots. In the spring of 2011, wild barley spik es were counted in wheat. Prevention of wild barley seed rain in wheat 71% reduced density and biomass of this weed in the cultivation of chick peas in the following year. Average wild barley spik e numbers in wheat in third year of rotation was declined 71. 9% due to no seed rain treatment in wheat in the first year of rotation. Delay in chick pea sowing time increased 68. 7% wild barley spik e numbers in wheat at the next year. Hand weeding in chick pea in no seed rain, and seed shedding of wild barley in wheat at initial year of the rotation, reduced 94. 6% and 88. 3% wild barley spik e numbers in wheat in third year of rotation, respectively. It seems that the correct strategy for wild barley management in wheat crop could be find in agronomic strategies lik e crop rotation.

To evaluate the effect of different cover crops management on the trend of growth indices of common bean (Phaseolus vulgaris) during the growth season in the presence and absence of weeds, an experiment was carried out as a factorial experiment based on the randomized complete block design with three replications in 2012-2013 growing season at the research farm of the Faculty of Agriculture, Ferdowsi University of Mashhad. Experimental factors were type of cover crops in three levels of erseem clover (Trifolium alexandrinum L. ), rye (Secale cereale L. ) and intercropping of berseem clover+ rye (50: 50), in two levels of seeding rate (recommended density and additive density), and three levels of mulch managements including herbicide+ mulch (cover crops killed by glyphosate and left the dead mulches on the soil surface), harvest+ mulch (cut the live cover crops and left them on the soil surface) and harvest (cut the cover crops and carried them out of the field). Results indicated that all treatments had significantly effects on the total weed density and dry weight and the maximum value of all growth indices. According to this, the LAI of common bean at chemical control (4. 68), hand-weeding (3. 96) and additive density of clover + rye with herbicide + mulch were the highest and total weed density and dry weight in this treatment, were the lowest. According to the results, the TDM at mentioned treatments were 747. 43, 708. 49 and 719. 77 g. m-2 and had the highest values. In cover crop treatments without herbicide application, remaining the cover crop residue was better than removing cover crop from soil surface. In addition, CGR (g. m-2. day-1) and RGR (g. g-1. day-1) of common bean had the similar trends to LAI and TDM. It was concluded that the additive density of clover + rye with herbicide+mulch was the best combination to achieve to highest values of common bean growth indices.