IRANIAN JOURNAL OF WEED SCIENCE
Year:2018 | Volume:14 | Issue:1 |Papers Count:10

A field experiment was conducted to determine the interaction effects of herbicide timing and doses on the control of Sorghum halepense in maize. The experiment was a split plot in randomized complete block design (RCBD) with three replications. Main plots were herbicide doses (0, 40, 60, 80, 100 g. ae of nicosulfuron) and sub-plots comprised herbicide timing (maize growth stages: 2-4 leaves, 4-6 leaves and 6-8 leaves). Standard dose response model was used to describe the relationship between weed biomass and herbicide doses at each herbicide application time. Estimated parameters showed that herbicide application delay increased U, L, ED50, ED90 parameters linearly. The highest yield of maize (20478. 8 kg/h) was obtained by 2. 5 lit/ha herbicide applied at 2-4 leaves of maize growth stage. Recommended dose of herbicide resulted in 12108. 74 kg/h maize yield when it was applied at 6-8 leaves maize growth stage. In summary, 1. 5 lit/ha herbicide applied at 2-4 leaves growth stage of maize gave acceptable control and decreased S. halepense biomass from 144. 9 to 41. 2 g/m2. The respected amount of weed biomass was not able to compete with maize and make damage. Results of the current study can be used in S. halepense management programs in maize fields.

This experiment was conducted during 2015-2016 in Karaj, Iran to investigate the effect of cover crops on weed control and the use of herbicide on establishment of cover crops as a split-plot arrangement in a randomized complete block design with three replications. Main factors were Festuca ovina, Festuca rubra, Agropyron desertorum, Bromus tomentellus and control (no cover crops, weedy) and sub factor was Bromoxynil + MCPA (Bromicide M. A EC. 40) herbicide in four levels: 0, 300, 450 and 600 gha-1. Based on the findings, B. tomentellus and F. ovina species had the highest cover crop dry mater (8 and 5 kg/ m2 respectively). B. tomentellus and F. ovina species had the highest reduction in weed densities (86% and 67%, respectively) and dry weights (81% and 71%respectively) compared to the control. The interaction between cover crops and herbicide on total dry weight of weeds was significant. The most common weeds of the experiment were Alyssum desertorum, Descurainia Sophia and Polygonum aviculare. The mean dry weight reduction of dominant weeds by cover crops compared to control for D. sophia, A. desertorum and P. aviculare were 83%, 71% and 89%, respectively. The highest dry weight loss of dominant weeds was belonged to B. tomentellus and F. ovina treatments. Based on the Shannon Wiener index, the highest reductions of diversity compared to the control (1. 5) were observed for B. tomentellus (0. 6) and F. ovina (0. 73).

Date palm is one of the most strategic and important products in the world. To investigate the effects of cover crops intercropped with date on bermudagrass (Cynodon dactylon L. ) biomass, an experiment was conducted in a randomized complete block design (RCBD) with three replications in Iranshahr, Baluchestan during 2011-2012. Treatments were sesbania (Sesbania sesban) 50 kg seeds/ha, alfalfa (Medicago sativa) 35 kg seeds/ha, pigeon pea (Cajanus cajan) 50 kg seeds/ha, vigna (Vigna radiate) 50 kg seeds/ha and sorghum (Sorghombicolor) 20 kg seed/ha. Results showed that the sesbania with 1937 gr/m2 in first year and 2326 g/m2 in second year, had the highest biomass in both years. 1937 g/m2. Vigna and pigeon pea with 159. 7 and 22. 8 g/ m2 in first year and 101. 7 and 50. 7 g/m2 in second year respectively, had the lowest dry matters. Weeds were controlled by sesbania, sorghum, vigna, pigeon pea and alfalfa 97, 59, 7 and 3 % in first year and 99, 74, 2, 10 and 95% in second year compared to control, respectively. The study indicated that sesbania and alfalfa had the highest mean biomass in both years and were the best treatment to control and reduce biomass of bermudagrass.

To evaluate the response of different garlic accessions to weed competition in Zanjan, west of Iran, a factorial experiment was carried out based on randomized complete block design with three replications in 2015-2016. Four variety of garlic (Hamedan 1, Hamedan 2, Hamedan 3 and Tarom) at two weed infestation conditions (whole season weed infestation and weed-free) were studied. The results indicated that responses to weed interference were significantly affected by accession. Hamedan 2 and Hamedan 3 accessions showed a considerable reduction in most traits under weed competitions while Tarom accession showed highest reduction that was most likely due to low competitive ability. Overall, Hamedan1 accession is recommended for cultivation in cool season regions such as Zanjan, due to the higher yield and lower yield decreases under weedy conditions.

Pondweed tolerance to flooding and most herbicides, as well as regrowth after hand weeding, has led the weed to be considered as an invasive species in paddy rice. Three experiments were carried out to provide a strategy for management of pondweed. In the first experiment, the interference of pondweed with Hashemi and Gohar rice cultivars at 0, 50, 100 and 150% of recommended NPK fertilizer were studied. In the second experiment, pondweed proliferation and colonization at the above fertilizer levels; and in the third experiment, the effect of water depth on the growth of this weed were investigated. The result of the first experiment showed that pondweed does not have significant effect on the yield of Gohar cultivar, but decreased the yield of Hashemi by 13-25%. Decreasing the fertilizer level to 50 and zero percent of recommended doses led to sharp decline in the performance of both rice cultivars in competition with pondweed. According to the results of the second experiment, the pondweed colony expansion in the 50% recommended dose of fertilizer treatment was twice that of 100% fertilizer treatment. The result of third experiment showed that, increasing the water depth to 7 and 14 cm led to 359 and 342 percent increase in pondweed shoot biomass in comparison to saturated treatment. In general, according to the results of this research, the reason for the outbreak and damage of pondweed can be attributed to the nutritional weakness and the deep and long flooding of the paddy fields. In case of efficient use of fertilizers, drainage and the use of appropriate cultivars, it is not necessary to spend a lot on frequent hand weeding and the presence of weed will not cause significant economic losses of rice.

Environmental conditions such as soil moisture have a significant effect on herbicides efficacy. In order to evaluate the effect of Othello herbicide in different soil moisture conditions on wild mustard and wheat, a greenhouse experiment was conducted as split plot based on randomized complete block design with three replications. Three levels of soil moisture including field capacity, 75% field capacity and 50% field capacity, and 0, 33, 66, 99, 132 and 165 grams of active ingredient of Mesosulfuron + Iodosulfuron + Diflufenican per hectare were the experimental treatments. Results showed that the concentration required to reduce the dry matter content of wild mustard by 50% in the field capacity was 71. 57 g. a. i /ha of herbicide, while in 75% and 50% of the field capacity, it was increased to 88. 69 and 112. 11 g of active ingredient per hectare, respectively. The required concentration to reduce 50% of dry weight of wheat in the field capacity was 86. 85 g. a. i / ha, while it reached to 102. 5 and 73. 95 g. a. i /ha at75% and 50% moisture content, , respectively. The results of the data showed that at 50% moisture content of the field capacity, lower concentrations of this herbicide would also have adverse effects on wheat.

Seed of wild oats can persist in the soil for a long time due to its dormancy. Studing the different factors affecting germination behaviors of this weed seeds will result in a properly control program. To quantify the rate of wild oat population's germination response to light and darkness, two experiments were performed in laboratory. The experimental design was a completely randomized design with three replications. Experimental treatments were temperature (10/5, 3, 5, 10 and 15 ◦ c), seed coat (with and without), and populations (Ahvaz, Kordestan and Shiraz). The results showed that germination responses to temperature changed based on seed coating. Seeds of wild oat populations were not germinated at constant temperatures of 3 and 5° C and also at fluctuating temperatures and Non-treated seeds germinated at 10 and 15° C. In the other words, increasing temperatures impact the germination velocity. The highest germination percentage (%87) occurred in the 10/5 C, in Shiraz population. Among populations, Ahvaz needed maximum growing degree days to reach 50% germination. Coated seed did not germinate at light or darkness in the 10/5 ° C and 3 and 5° C. Significant difference were evident in germination percentage of coated and without coat seeds of wild oat population. This indicates the role of genetic factors and environmental conditions during plant growth and the germination behavior of seeds. Precise and accurate prediction of the time of seed germination and emergence based on feedback of environmental conditions should be considered to performe the effective control method or methods in integrated weed management.

This experiment was conducted to evaluate the effects of the pre planting herbicides including Trifluralin (Treflan 48% EC) and Ethalfluralin (Sonalan 33. 3% EC), pre emergence herbicides including Oxadiazon (Ronstar 25% EC, 12% SL), Simazine (Princep 4L) and Prometryn (Gasagard 80% WP) and post emergence herbicide including Linuron (Afalon 50% WP, 45% SL) on weed control and yield, yield components, seed yield, essence yield and essence efficiency of cumin in a randomized complete block design with three replications. Five dominant weed species i. e. Chenopodium album, Fumaria officinalis, Polygonum avicular, Hordeum murinum and Triticum aestivum were identified. Results showed that effect of the herbicides on density and dry weight of each and total weed species were significant. In this study, all herbicides significantly decreased total weed density compared to weedy check. The order of reduction in total weed density was hand weeding> Ethalfluralin> Oxadiazon> Trifluralin= Linuron= Simazine> Prometryn. The highest and lowest total dry weight of weeds were obtained in weedy check and hand weeding, respectively. Among various herbicides treatments, Ethalfluralin and Oxadiazon had the inhibitoriest effects on the total dry weight of weeds in comparison with weedy check (97. 40 and 84. 31% respectively). The results also showed that there were significant differences among various herbicide treatments on cumin density, number of umbrella per plant, number of seed per umbrella, 1000-seed weight, seed yield, and essence yield and efficiency. The highest and lowest seed and essence yield were obtained in hand weeding and weedy check, respectively. After weeding treatment, Ethalfluralin application had the highest seed yield and essence yield.

To evaluate the response of annual weeds to interaction between imazethapyr herbicide doses and soil moisture in bean fields, a split plot experiment based on randomized complete blocks design with three replications was conducted. Main plots included three different moisture regimes (60, 75 and 90 mm of accumulated evaporation; equal to 100, 80 and 60% of bean water requirement respectively) and sub-plots were five doses of imazethapyr (0, 25, 50, 75 and 100 percent of the recommended dose). The result illustrated that the interaction effects of herbicide doses and soil moisture on the biomass of weeds were significant. Under low soil moisture conditions, Amaranthus retroflexus and Chenopodium album grew more and the highest amount of weed biomass (396. 81 gr /m2) was obtained from 60% of bean water requirement and without weed control treatment. Also, based on the three-parameter dose-response model, the predicted ED50 parameters in the 100, 80 and 60% moisture regimen, were 32. 45%, 56. 59% and 73. 46%, of the recommended dose respectively. These results showed that in the less soil moisture, the amount of required herbicide to reduce the 50% of weed biomass, increased. The highest yield (4133. 84 kg/h) was obtained from 100% moisture regime and 100% recommended dose of herbicide. According to these results, when soil moisture content is appropriate, the herbicide efficiency in weed control and also the bean yield will increase. The results of this experiment can be used to predict the appropriate dose of herbicide in variable climatic conditions of Iran.

In order to evaluate the efficacy of Isoxaflutole (SC480) on weed control in Chickpea (Cicer arietinum L. ) fields, experiments were carried out in Kermanshah, Kurdestan and Lorestan provinces in a randomized complete block design with four replications. Treatments consisted of applications of pre-emergence isoxaflutole (SC480) at 0. 2, 0. 3 and 0. 4 L. ha-1 of commercial formulation, post-emegence isoxaflutole at 0. 2, 0. 3 and 0. 4 L. ha-1 of commercial formulation, post-emergence pyridate (EC60%) at 2 L. ha-1 of commercial formulation and hand weeding. Weed percent damage based on EWRC scores at 30 days after post spraying, weed density reduction (%), weed biomass reduction (%) were measured. According to the results, the best treatments in Kermanshah for grain yield of chickpea were pre-emergence isoxaflutole at rates 0. 2 and 0. 3 L. ha-1 with 669 and 632. 5 kg ha-1 that reduced weed density %79 and %80. 5 respectively. In Kurdestan, pre-emergence isoxaflutole at rate 0. 2 L. ha-1 was considered as the most suitable treatment with 80% reduction in weed density and 1118 kg ha-1 grain yield. In Lorestan, pre-emergence isoxaflutole at rate 0. 2 and 0. 3 L. ha-1 reduced weed population at 89. 5% and 91. 5% respectively. The highest grain yield in Lorestan belonged to pre-emergence isoxaflutole at rates 0. 2 and 0. 3 L. ha-1 at 742 and 812. 5 kg. ha-1. According to the results in the three locations, application of pre-emergence isoxaflutole at rate 0. 2 L. ha-1 of commercial formulationis suitable for weed control in spring chickpea.