Improved Activity of Imazethapyr onJimsonweed (Datura stramonium L.)

Introduction: An adjuvant has been defined as ‘a material that when added to a spray solution improves or modifies the performance of an herbicide’. There are five categories of adjuvants including drift retardants, extenders, stickers, wetters, and penetrants. The latter can chemically be divided into mineral or vegetable groups. Although some reports have found that vegetable oils are less effective than mineral oils, in view of the environmental concerns, the use of vegetable oils seem to be a suitable alternative to mineral oils because they offer a series of advantages such as being biodegradable and renewable resources. The plants essential oils are extracted from the medicinal plants not only have an adjuvancy activity at low concentrations but also have an herbicidal activity at high concentrations. It is believed that the benefit of vegetable oils as adjuvant can be related to their ability (i) to increase the drying period of the spray droplets during their fly time before impacting the leaves, (ii) to prevent bouncing off after impacting the leaves, (iii) to decrease contact angle of the droplet on the leaf surface and improve the spreading of them on the leaf surface, (iv) to delay crystallization of the active ingredient on the leaf surface, (v) to reduce the volatizing and photo-decomposing period of the herbicide active ingredient, (vi) to act as a penetrant agent on the leaf epicuticular wax in order to enhance the penetrability of the herbicide active ingredient into the plants. A fundamental part of all agrochemical researches is search to detect the natural chemicals offering adjuvancy properties to enhance the biological activity of agrochemicals. Therefore, we conducted a dose-response experiment to determine the potential influence of Blackseed, Fennel, Olibanum, and Rose oils as oily based-adjuvants in enhancing the imazethapyr activity against jimsonweed. Materials and Methods: The jimsonweed seeds were collected from plants in the fields of Qazvin and were stored in the dark at room temperature until further use. Bioassays were conducted in a greenhouse located on the Ferdowsi University of Mashhad, Iran. The seeds were washed every 1 h for 7 days for a total of 168 washings to remove seed germination inhibitors according to Andersen. They were sterilized with 5% (v/v) sodium hypochlorite solution for 10 min and rinsed with distillated water twice. Then, 25 jimsonweed seeds were sown in 2 L plastic pots filled with a mixture of sand, clay loam soil, and peat (1:1:1). The pots were irrigated three times a week. At the 1- and 2-leaf stage, the seedlings were thinned to 4 plants pot-1 and fertilized twice with 20 mL of a N:P:K (20:20:20) fertilizer with a concentration of 3% (w/v). The pots were irrigated every three days with tap water. Treatments were sprayed at the 4-leaf stage. Experimental design was a factorial arrangement with the 5 doses of imazethapyr (Pursuit® 10% SL) and the four essential oils at concentrations of 0.5 and 1% (v/v) in a completely randomized design with four replications. The emulsifier alkylarylpolyglycol ether was used to emulsify the substances in spray solution (95% oil + 5% emulsifier). Treatments were applied at 180 L ha-1 at 200 kPa using a calibrated moving boom sprayer with an 8002 flat-fan nozzle. Three weeks after spraying, biomass from each pot was collected and then weighted after oven-drying at 75°C for 48 h. The data were subjected to a non-linear regression analysis using the following logarithmic logistic dose-response model described. The relative potency that is the horizontal displacement between the two curves was calculated by the ratio of doses producing the same response. Results and Discussion: The slope of dose-response curves for jimsonweed to imazethapyr without or with each adjuvant were significantly similar as indicated by the same slope (b), so that they could be considered to be parallel. This indicates that the adjuvants were biologically inactive if they are used alone (without herbicide) at the tested concentration. Based on shoot fresh and dry weights of jimsonweed, the values of ED10 (6.47 and 7.50 g a.i. ha-1), ED50 (18.08 and 19.01 g a.i. ha-1), and ED90 (50.48 and 43.54 g a.i. ha-1) were obtained. All these values decreased in the presence of all the adjuvants. The relative potency values were significantly different from 1, indicating a significant enhancement in the imazethapyr activity when the adjuvants were added to the spray solution. Based on fresh weight of jimsonweed, the imazethapyr activity was improved up to 4.61-fold with addition of Fennel oil at 1% (v/v). Nonetheless, based on fresh weight of jimsonweed, it was improved up to 4.50-fold with addition of Olibanum at 1% (v/v). Based on dry weight of jimsonweed, the adjuvants were ranked according to their performance in improving imazethapyr activity as follows: Fennel > Olibanum > Blackseed > Rose when they were applied at 0.5% (v/v). But, at 1% (v/v), they were ranked as follows: Olibanum > Blackseed > Rose > Fennel. There are no reports available about the effect of the tested adjuvants as an adjuvant for herbicide, but similar studies were reported by Cabanne who found that the clodinafop-propargyl activity was enhanced up to 5- to 6-fold with adding pine essential oil (Pinus pinaster Ait.) to spray solution at 0.5% (v/v). Vegetable oils have also been found to be effective adjuvants for several post-emergence herbicides. Only in case of Blackseed oil, increasing the concentration had a significant effect to enhance the imazethapyr activity as compared to others. The benefit of concentration effect has formerly observed by researchers who reported that there was a strong concentration effect for rapeseed oil since their influence on phenmedipham and glyphosate uptake and activity was lower at 0.1% than at 1% (v/v). Conclusion: Since the main barrier for diffusing a hydrophilic herbicide such as imazethapyr into the leaf tissue is hydrophobic cuticle, thus oil based-adjuvants have been known to work best with them. On the other hand, a shift from non-environmentally friendly adjuvants to environmentally friendly (namely from mineral oil-based adjuvants to vegetable oil-based adjuvants) in adjuvant trend has been occurred due to being biodegradable and renewable. Thus, it is necessary to look for new essential oils offering adjuvancy properties to improve the efficacy of such foliar-applied herbicides because it is a straightforward approach to reduce the risk of adverse side-effects of herbicide via reducing herbicide dose needed to control suitable weeds. From the present study, it could be concluded that the oils Blackseed, Fennel, Olibanum, and Rose showed a strong adjuvancy properties for imazethapyr against jimsonweed and hence they could be suitable for developing and testing as an oily based-adjuvant. Though it is questioned whether crop selectivity could be threatened when these adjuvants are applied, further work is required under field conditions to answer this question

Evaluation the Effect of Corn (Zea mays L.) Sowing Pattern and Nitrogen Application Method on Herbicide Optimizing and Reducing Foramsulfuron (Equip®) Dose

Introduction: In the whole agro ecosystems, weeds had existence as unwanted plant that control of them is necessary. The competition between weeds and corn for moisture, light, nutrients during the growth season is induced reducing the quality and quantity of corn yield. Although the corn is high and powerful crop but is sensitive to competition with the weed and reduction of yield has been reported over 30%. Since the weeds are adapted to conditions, they are successful to completion and reducing the yield. So weed management is important in corn production. Chemical control has not been the unique and best way to manage the weeds and it reduce the sustainability of agro ecosystems. Although developing the herbicides, reduce the pressures caused by the weeds, but by developing rapidly the weed resistance to herbicides and increasing the environmental concerns and its high cost, today need to new, more immune and sustainable techniques for weed management. The main approach for sustainable weed management in an integrated weed management program is increasing crop competitiveness with weeds to reduce herbicide use. In this regard, the planting date, crop rotation, planting density, intercropping, planting pattern, fertilizer type, rate and application method are some of the most crop management strategies. Among the nutrients necessary for plants, nitrogen is the most nutrient in plant competition. Therefore, its application management plays a key role in reducing weed interference with crops and reduced herbicide use. Foramsulfuron herbicide from ALS inhibitors is a post-emergence sulfonylurea herbicide for the control of grasses and certain broadleaf weeds in maize. Unfortunately, these herbicides are also notorious for their ability to select resistant weed populations. Now, there are more weed species that are resistant to ALS-inhibiting herbicides than to any other herbicide group. In several cropping systems, ALS-inhibiting herbicides were used repeatedly as the primary mechanism of weed control. These herbicides exert strong selection pressure because of their high activity on sensitive biotypes at the rates used and because of their soil residual activity. So, the primary objective of this study was to determine the effect of some crop management strategies including sowing pattern and fertilizer application methods on herbicide optimizing and reducing foramsulfuron dose. Materials and Methods: In order to evaluate the effects of corn sowing pattern and nitrogen application methods on optimizing and reducing of foramsulfuron dose, a field experiment was conducted as split factorial, based on randomized complete block design with three replications at the Research Station, of Faculty of Agriculture, Ferdowsi University of Mashhad, in 2012. Treatments included, corn sowing methods (single-row with 75 cm distance, twine row as parallel on 75 cm width ridges sides and double row as zigzag on 75 cm width ridges sides) as main plots, factorial of nitrogen application methods (broadcast and band application), nitrogen source for fertilization was urea (400 kg ha-1), and foramsulfuron doses (100, 75, 50 and 0% of recommended dose (2 liter of commercial doses) applied at 4th corn leaf stage as sub plots.Weed density and frequency were recorded 10 days before corn harvesting and total weed biomass, corn biomass and seed yield were recorded at the end of the experiments per 1 m-2. Analysis of variance of data was carried out with SAS software and for means comparisons LSD (p≤0.05) test was used. Also The rectangular hyperbolic equation to describe the relationship between density and weed biomass and biomass and grain yield of maize was used Results and Discussion: Evaluation of weed flora indicated that 6 weed species (including 5 dicot. and 1 monocot.) including red root pigweed (Amaranthus retroflexus L.), black nightshade (Solanum nigrum L.), lambsquarters (Chenopodium album L.), field bindweed (Convolvolus arvensis L.), purslane (Potulaca oleracea L.) and barnyard (Echino clhloacrussgalli L.) were dominant species, with high evenness in the experimental plots. Amongst the mentioned weed species, the red root pigweed included about 74% of relative frequency and 80% of relative biomass of total weed biomass. Also results showed that the effect of sowing pattern on biomass and density of weeds and corn traits was not significant. However, band application of nitrogen versus broadcast application, increased weed density and biomass per m-2 25 and 10 percent, respectively and in the same way, increased corn height, kernel yield and biomass per m-2 7, 30 and 25 percent, respectively. Conclusion: It was concluded that by using double row sowing pattern along with band application of nitrogen, we can reduced foramsulfuron dose nearly 50 percent

Evaluation of PRE and POST Herbicides on Growth Features, Nodulation, and Nitrogen Fixation of Three Cultivars of Chickpea (Cicer aritinium L.)

It is exceptionally difficult to have productive farming without the use of herbicides. It has been found that they create difficulties in the growth and biological nitrogen fixation of some legume crops after their application. Adverse impacts may result from a direct effect of the herbicide on rhizobial growth and/or an indirect effect on plant growth. In order to study the effect of some PRE and POST herbicides on nodulation, nitrogen fixation, and growth characteristics of three chickpea cultivars, a greenhouse trial was conducted in a completely randomized design with factorial arrangement and three replications. Pyridate, imazethapyr, and trifluralin were applied with the recommended rates of 1100, 100, and 720 g ai ha−1, respectively, and also non-treated control on three chickpea cultivars (ILS482, Hashem, and Kaka). The results showed that trifluralin and pyridate herbicides had the highest and the least negative impact on growth characteristics of three examined cultivars. Pyridate showed a positive effect on vegetative characteristics but nodulation and total nitrogen contents in the shoots of chickpea cultivars decreased significantly. Results also revealed that root and shoot growth, nodulation, and nitrogen fixation diminished significantly when imazethapyr and trifluralin were applied to Hashem and ILC482 cultivars. It seems that pyridate is an appropriate herbicide for broadleaf weed control in chickpea fields. © 2020, Korean Society of Crop Science and Springer

Investigations on the Cardinal Temperatures for Germination of Alhaji pseudalhagi

In order to investigate the germination characteristics and cardinal temperatures of biotype Alhaji pseudalhagi, A laboratory experiment was conducted randomized completely design with four replications of 25 seeds. Various constant temperatures 5, 8, 10, 15, 20, 25, 30, 35, 40, 45 and 50ºC were considered. The characteristics such as percentage of seed germination, rate of seed germination, the time of reaching 50% seed germination were recorded. In order to select best estimate of germination criteria based on three regression models namely: Five-parameters Beta(FPB), Intersected-lines(ISL) and Quadratic Polynomial(QPN) models. The effect of temperature on rate and percentage of germination was significant. The highest germination percentage(GP) was within the range of 20-35ºC while the highest germination rate(GR) occurred in 25ºC. Best model fit over the entire temperature range was obtained by the FPB model. Based on the regression between germination rate and temperature in biotype, the cardinal temperatures(Tbase, Topt and Tmax) were: (7.2-8.8), (27.5-30.6) and (42-50.5) °C, respectively

Effect of Nitrogen Fertilizer on Weeds Growth and Emergence and Yield and Yield Components of Corn (Zea mays L.)

Introduction: Corn is one of the important crops of poaceae family which has important role in supplying food for human societies. Corn is third food crop in world and it has high potential compare to other crops because of its C4 photosynthetic pathway. In addition, corn is a strong and fast growing plant but it is sensitive to competition with weeds. According studies, there are 25 to 30 problematic weeds in corn farms which they include annual and perennial species. Annual weeds life cycle is similar to corn life cycle, there for the most problem of weeds in corn is summer annual weeds. Damage of weeds is different and it depends on weeds density, species composition, time of emergence, crop variety and other factors. While non control of weeds depending on those density and Variety, corn yeild may be decrease of 15 to 90 percent. Weeds which germinate in a short time can compete with crop on light, water and nutrition sources. Most of the weeds show better reaction to fertilizers compare with crops. This subject is due to weeds ability to nutrition absorption and aggregation and their high performances. Most of the weeds species are more responsive than crops to application of nitrogen fertilizer. Furthermore, the growth of most of the weed species increases with increasing nitrogen. Therefore, the increase of nitrogen in farming systems can have impacts on weeds and crops competitiveness. However, weeds compete with crop about using light, nutrient, water and soil space and the result of this competition is yield losses. Moreover, nitrogen is necessary to increase yield and nitrogen fertilizer enhances corn competitiveness, especially early in the season due to the slow growth of the plant and is necessary to achieve optimal performance. Excessive of nitrogen fertilizer during the growing season is benefit for weeds. Therefore, in order to study the effects of nitrogen fertilizer in combination with weeds management on yield and yield components of corn and weeds growth and emergence, a field study was conducted in research Station of Natural Resources Research Centre, Kerman province. Materials and Methods: This experiment was conducted using a randomized complete block design with three replications. The treatments consisted of different levels of nitrogen in four levels (0, 80, 160, 240 kg ha-1) urea fertilizer (46%). In addition, for assessment the effect of experimental treatments, each plot separated into two parts (complete control and non-control of weeds). Preparing the field was done with autumn plowing and spring disc. Corn seeds (single cross 704) were planted on rows in the spring with hand and with the density of 71000 plants per hectare with row spacing of 70 cm and 20cm. Irrigation was performed on average every7 days. Weeds in the control treatment were weeding by hand twice during the growing season. Results and Discussion: The results showed that nitrogen application in combination with weeds control increased yield and yield components of corn and the other growth traits, significantly. The maximum corn yield observed 12/8 kg under high nitrogen treatment (240 kg ha-1) with 88/82% increase compare with non-fertilizer treatment. Moreover, increase in nitrogen imposed a significant positive affect on height, yield and yield components including (Length and ear diameter and ear dry matter, the number of grains in row and the number of rows in ear, hundred grain weight). Nitrogen is one of the factors affecting the development of leaf area per plant and therefore, the development of the corn canopy. It seems that the increase of nitrogen during the tassel stage and seed formation which are the most sensitive stages to nitrogen absorption and photosynthesis, increased the length of ear. In addition, results of the experiment indicated that control of weeds had significant effect on different growth factors. Furthermore, the increase nitrogen rate caused to weeds emergence rate and dry weight increase. The greatest dry weight of weeds was observed at the highest level of fertilizer (240 kg ha-1). It can be said that in the latter stages of growth that competition was effected and caused dominance strong species, increasing fertilizer after a certain amount (160 kg ha-1) had no effect on the dry matter competing species in the field. Therefore, it seems that competition in the early stages is very important. Conclusion: C4 weeds such as Barnyard grass and Slender foxtail and Redroot pigweed, showed more growth increase compare with C3 species. Therefore, C4 species are more dominance than C3 species in competition and increased germination rate for these weeds with increasing nitrogen rate. As a result, we should control these weeds early in high nitrogen rate. So, nitrogen fertilizer had positive impact at different forms on the plants, resulting in the use of this nutrient should be done more researches

Optimizing the Efficacy of Some Post Emergence Herbicides of Sugar Beet using Adjuvants and Split Application of Herbicide

Introduction: Increasing the environmental concerns emerged from the extensive use of herbicides have caused to work and introduce new approaches for their application by weed scientists. Nonetheless, weeds limit crop production especially when herbicides are removed from the weed management strategies. Optimizing herbicide doses, by increasing farmer’s knowledge about various options of herbicide application, is one of the most important strategies for reducing herbicide application. Tank-mixed herbicides, adjuvants, and split application of herbicide are more interesting, users friendly, and effective to implement this approach. Post-emergence herbicides require adjuvants to be tank-mixed or built into the formulation to enhance their performance. Utilizing these methods is very essential for crops which are very weak competiveness against weed, because of herbicides application is a common method in them. Sugar beet is an important crop grown in the most cultivation areas of Iran under cultivation about 82.5 thousand hectares over average yield 42 ton ha-1. This study was done to increase the performance of some post-emergence herbicides for controlling weeds in sugar beet using adjuvants, tank-mixed herbicide, as well as herbicide split-applied herbicide treatments. Materials and methods: A factorial experiment based on randomized complete block design with three replications was conducted at the research field of Ferdowsi University of Mashhad (985 m altitude, longitude 59˚ 28´ and latitude 36˚ 15´) in 2013. The factors included the method of herbicide application (full and split application), herbicides (chloridazon (5 Kg ha-1) plus desmedipham (6 L ha-1), desmedipham plus phenmedipham plus ethofumesate (3 L ha-1) and chloridazon (5 Kg ha-1) plus desmedipham plus phenmedipham plus ethofumesate (3 L ha-1)), and adjuvants (Non-adjuvant, Adigor (%1.5 v/v), Citogate (%0.2 v/v) and Ammonium sulfate (%0.5 v/v)). Furthermore, two control treatments were considered as weed free and weed infested for each replication. Herbicides were applied with a backpack sprayer equipped with 8002 flat fan nozzles that calibrated to deliver a spray volume of 400 L ha-1 at 275 kPa. Commercial sugar beet seeds, ‘005’ Monogerm provided from Improvement Research Institute of sugar beet, Karaj were planted on April 25 by hand to the depth 2 to 3 cm of the soil. Each plot consisted of four rows of sugar beet spaced 50 cm apart and 5 m long and density of sugar beet was 12 plants per m2. Seedbed preparation operations consisted of moldboard plowing, double disking and application of N at 69 kg.ha-1, P2O5 at 67.5 kg.ha-1 and K2O at 50 kg.ha-1 was done according to the soil test and the fertilizer recommendations. Irrigation was performed once a week. In order to determination of total weed biomass and density, weeds existing in the area 1×1 m2 were collected, counted and weighted. Also sugar beet root yield and biomass was recorded for same area. Data were subjected to ANOVA using the PROC GLM procedure in SAS Version 9.4 and means were compared using Fisher’s protected LSD test at the 0.05 level of significance. Drawing of figures were done by SigmaPlot Version 12.5. The relationship between sugar beet root yield and weed density and biomass were described with hyperbolic decay 2 parameters model. Results and discussion: In the experimental plots, we observed ten species of broadleaf weeds among which redroot pigweed (Amaranthus retroflexus L.), common lambsquarter (Chenopodium album L.), black nightshade (Solanum nigrum L.), purslane (Portulaca oleraceae L.), and field bindweed (Convolvulus arvensis L.) have higher relative frequency and density than others. The results showed that the highest sugar beet root yield, as value 110.29 ton ha-1, occurred in split application of chloridazon plus desmedipham with Adigor. Furthermore, the highest sugar yield obtained from the plots with split application of chloridazon plus (desmedipham plus phenmedipham plus ethofumesate) with Adigor at 16.10 ton ha-1. In split application of desmedipham plus phenmedipham plus ethofumesate without adjuvant, the lowest sugar beet root yield and sugar yield were recorded 50.07 and 7.57 ton ha-1, respectively. Full application of chloridazon plus (desmedipham plus phenmedipham plus ethofumesate) with Adigor with %17 sugar content, and split application of desmedipham plus phenmedipham plus ethofumesate Adigor with %11.74 sugar content had the highest and lowest, respectively. Split application of chloridazon plus desmedipham with Citogate and full application of chloridazon plus (desmedipham plus phenmedipham plus ethofumesate) with Citogate indicated completely weed control, and full and split application of desmedipham plus phenmedipham plus ethofumesate with ammonium sulfate had the lowest performance of weed control. The results of the regression analysis showed that the highest yield of sugar beet occurred when total weed density or biomass are zero (104.62 and 101.41 tonha-1 were estimated, respectively). Also, when weeds density and biomass increased to 24 plants m-2 or 479.13 g dry matter m-2, the root yield of sugar beet will be decreased by 50%. Conclusion: The results of this study showed that split application of chloridazon plus desmedipham with Adigor or Citogate, created the highest sugar beet root yield and appropriate weed control among all treatments. In contrast, split application of desmedipham plus phenmedipham plus ethofumesate without any adjuvant had the lowest performance of weeds control. It was concluded that the most important factor among the experiment factors was the type of herbicide or herbicide combination