جستجوی مقالات مرتبط با کلیدواژه « nozzle size » در نشریات گروه « گیاهپزشکی »

Diclofop-methyl is labeled for use in wheat and barley to control many grassy species, e.g., the genus Avena. Efforts should be made to use diclofop-methyl correctly, allowing the reduced doses to be applied. The response of herbicides to spray volume is different. After determining a suitable spray volume for a foliage-applied herbicide, the next step is to adjust it. The spray volume can be adjusted by two methods the change in application speed or nozzle size. If less spray volume is necessary to apply an herbicide, it is needed to increase application speed. It causes the spray droplets to be more bounced or shattered from the leaf surface, causing the herbicide not to achieve optimal efficacy. Therefore, selecting a smaller orifice nozzle is much more applicable, of course, if the spray drift is controlled. The surface tension of water, which is used to spray herbicides, can be slightly reduced after adding the formulation of herbicides. Therefore, the relatively high surface tension of the spray solution poses three main problems. First, the spray droplets can easily be bounced off the leaf surface. Second, those remaining on the leaf surface after impact have a relatively spherical shape. Third, the crystalline wax in the cuticles, is considered an essential barrier to penetrating herbicides into the leaf tissues. It is well-established that the three main issues mentioned above can be addressed by selecting a suitable surfactant to add to the spray solution. This addition enables optimal efficacy of the herbicide. Consequently, numerous previous studies have highlighted the superiority of trisiloxane surfactants over non-silicone surfactants in enhancing herbicidal activity. This study aims to assess whether the effect of spray volume, adjusted by changing nozzle size, on the herbicidal activity of diclofop-methyl could be influenced by two types of trisiloxane surfactants – one with super wetting properties and the other with non-super wetting properties.

A greenhouse trial was performed as a dose-response relationship at the Bu-Ali Sina University, Hamedan, Iran. The experiment was designed as a four-factor completely randomized design. The first factor was the dose of diclofop-methyl (Illoxan® EC 36%) including 0, 112.5, 225, 450, 900 (labeled dose), and 1350 g ha-1. The second factor was spray volume, including 60, 120, 240, and 480 L ha-1, which were adjusted using 1100075, 110015, 11003, and 11006 flat fan nozzle, respectively. The third factor was two types of trisiloxane surfactants, Break-Thru® S 233 having a non-super wetting property and Break-Thru® S 240 having a super wetting property. Both are non-ionic surfactants and manufactured by Evonik company in Germany. They formed their critical micelle concentration (CMC) at 0.1% v v-1 at which the surface tension of distilled water (72.1 mN m-1) containing Break-Thru® S 233 and Break-Thru® S 240 was measured to be 24.1 and 22.6 mN m-1, respectively. The fourth factor was surfactant concentration, including 0, 0.0125, 0.025, 0.05, 0.1, 0.2, 0.4, and 0.8% v v-1 (a range from ⅛ to 8 CMC, respectively). A compressor sprayer was used to apply the treatments at 300 kPa spray pressure. A nonlinear regression analysis was conducted to analyze the ‘drc’ using the software R.

A 40% increase in the ED50 value occurred with increasing the spray volumes from 60 to 480 L ha-1 (536.4 and 865.1 g ha-1, respectively), indicating a negative relationship between diclofop-methyl activity and spray volume. Adding Break-Thru® S 233 at 0.025% v v-1 to 60, 120, 240, and 480 L ha-1 spray volumes caused a 1.16, 3.31, 2.04, and 2.13-fold decrease in the ED50 value compared with no surfactant at their corresponding spray volumes, respectively. While, adding Break-Thru® S 240 at 0.025% v v-1 to 60, 120, 240, and 480 L ha-1 spray volumes caused a 1.39, 1.32, 1.34, and 1.19-fold decrease in the ED50 value compared with no surfactant at their corresponding spray volumes, respectively. A decrease in the ED50, attributed to the addition of surfactants, signifies an enhanced activity of diclofop-methyl against sterile oat. This improvement may stem from a reduction in the surface tension of the spray solution, resulting in an expanded retention and/or spreading area of the spray droplets on the leaf surface. This, in turn, facilitates increased penetration of the herbicide into the leaf tissue. These findings indicate that Break-Thru® S 233 works better when added at low concentration to a low-volume spray solution, while Break-Thru® S 240 works better when added at high concentration to a low-volume spray solution. It can be attributed to the difference in the wetting property of surfactants. The natural relationship between diclofop-methyl activity and spray volume at higher concentrations of Break-Thru® S 233 may be related to its phytotoxic effect, resulting in an antagonism effect on diclofop-methyl activity against sterile oat. In the case of Break-Thru® S 240, the relationship mode between diclofop-methyl activity and spray volume was not affected by surfactant concentration indicating the lack of phytotoxic effect by this surfactant.

The current study revealed a negative relationship between diclofop-methyl efficacy and spray volume, which was adjusted by nozzle size. Although this finding differs from a previous study in which spray volume has been adjusted by application speed, they showed that the effect of spray volume on the herbicide’s efficacy depends not only on herbicide but also on how it is adjusted. The smaller, more concentrated spray droplets are necessary to get a better action of diclofop-methyl against sterile oat. However, the negative relationship observed between diclofop-methyl efficacy and spray volume could also be observed with two types of trisiloxane when they surfactants, were used at 0.0125 to 0.1 v v-1. While, when they were used at 0.2 to 0.8% v v-1, the relationship mode changed from negative to neutral for Break-Thru® S 233, but it did not change for Break-Thru® S 240. Moreover, Break-Thru® S 240 works better when added at high concentration to a low-volume spray solution due to the danger of spray run-off, while Break-Thru® S 233 works better when added at low concentration to a low-volume spray solution due to its phytotoxic effect.

Herbicides should be sprayed on weeds after diluting in water. Since the spray volume can affect the efficacy of herbicides; therefore, selecting an appropriate spray volume has always been considered a simple, inexpensive and available method to optimize the efficacy of herbicides. Changing the sprayer speed and the nozzle size are two possible methods to adjust the spray volume. If a very low or high spray volume is required to achieve optimal herbicide efficacy, the applicability of the first method will be problematic. For this reason, the method of changing the nozzle size always seems to be more feasible.. When a graminicide is sprayed with a single flat fan nozzle, which is currently the most common type of nozzle available to most Iranian farmers, the spray droplets which move perpendicular to the ground are mostly oblique to the leaf surface of the grass, having erect leaves. Hence, it is likely that a large number of the spray droplets bounced from the leaf surface to the soil. A twin flat fan nozzle can create two non-vertical sprays, reducing the possibility of impacting obliquely the spray droplets to the leaf surface. Therefore, the bouncing of spray droplets from the leaf surface is significantly reduced. To date, the efficacy of twin symmetrical and asymmetrical flat fan nozzles has not been compared. On the other hand, the effect of spray volume on haloxyfop-r-methyl efficacy against wild barley has not been evaluated. Therefore, this experiment was intended to fill the gaps mentioned in science.

To compare the efficiency of single, twin symmetrical and twin asymmetrical flat fan nozzles under different spray volumes, a dose-response experiment was performed in the Research Greenhouse of Bu-Ali Sina University. In this experiment, seven doses of haloxyfop-r-methyl (0, 10.8, 21.6, 43.2, 64.8, 84.4 and 108 g a.i. ha-1) were used using three types of nozzles (single flat fan, twin flat fan 2020 and twin flat fan 3070) in six sizes of them (110015, 11002, 110025, 11003, 11004 and 11005, which create the spray volumes of 150, 200, 250, 300, 400 and 500 L ha-1, respectively) were sprayed on wild barley at a three-leaf stage. Simultaneously with spraying 108 g a.i. ha-1, another experiment was performed as a factorial in a completely randomized design. In this experiment, the amount of spray settling from three types of nozzles in six sizes of on moisture-sensitive papers was evaluated in three situations. Paper No. 1 was mounted horizontally on the ground and papers No. 2 and 3 were mounted vertically facing the back and back of the nozzle, respectively. 

In paper No. 1, in all types of nozzles, more surface of the paper was wetted by increasing the nozzle size (spray volume). In all types of nozzles at 11003, 11004 and 11005, the highest wetting rate was provided (100%). The lowest wetting rate was obtained with twin flat fan 3070 at 110015 (7.3%). In paper No. 2, in all types of nozzles, more surface of the paper was wetted by increasing the nozzle size. The highest wetting rate (100%) was observed with single flat fan and twin flat fan 2020 nozzles at 11003, 11004 and 11005. The lowest wetting rate (24-19%) was observed with single flat fan nozzle at 110015 and 11002. In paper No. 3, in two twin flat fan nozzles, more surface of the paper was wetted by increasing the nozzle size. A single flat-fan nozzle could not wet the paper at all. In general, the performance of the nozzles used in this experiment is twin flat fan 2020 > single flat fan = twin flat fan 3070. In all types of nozzles, with increasing the size of nozzles (spray volume), the rate of haloxyfop-r-methyl is required to reduce 50 and 90% of the dry weight of wild barley (ED50 and ED90) increased significantly, indicating a decrease in the efficacy of haloxyfop-r-methyl against wild barley. As the best treatment, the lowest values of ED50 and ED90, which were equal to 9.34 and 38.21 g a.i. ha-1, respectively, were obtained with twin flat fan 2020 at 110015. Increased efficacy of haloxyfop-r-methyl when spray volume was reduced can be explained as follows small size nozzles create a greater small droplet. Smaller droplets may give better spray retention over the leaf surface, resulting in increased efficacy of haloxyfop-r-methyl. In low spray volume, the higher concentration of herbicide in the spray solution may create a greater concentration gradient between the spray solution and leaf, increasing the diffusion of herbicide into the leaf.

Although the spray coverage increased with increasing spray volume for haloxyfop-r-methyl, it has an adverse effect on its efficacy. Therefore, smaller and more concentration droplets resulted in greater control of wild barley with haloxyfop-r-methyl than did larger and more dilution droplets.