عنوان مقاله [English]
Introduction: The herbicide application has caused some environmental problems. Therefore, optimal application of herbicides was followed in recent years. For this purpose, it is essential to minimize the exo-drift and/or endo-drift of spray droplets. The amount of exo-drift and/or endo-drift is directly related to the size of spray droplets. By decreasing the size of spray droplets, the exo-drift increases and the endo-drift decreases (34). This intricate issue is a stimulus to develop the types of nozzles in different sizes (color) producing different sizes of spray droplets at different spraying pressures. Such a development in the production of nozzles has caused difficulty and confusion in selecting a suitable type of nozzle (2). On the other hand, the agriculture sector is faced with water crisis in recent years. Considering that water is the most important carrier of herbicides, selecting a suitable spray volume is thus necessary. According to previous studies (26), the efficacy of different herbicides can influence spray volume negatively (30), neutrally (29), or positively (12). So far, the effect of spray volume on the efficacy of cycloxydim against any weed has not been investigated. Also, since the types of triplet flat fan nozzles have been recently developed, no investigation has been done on their performance compared to the types of single and twin flat fan nozzles. The current study aimed to fill this knowledge gap.
Materials and Methods: The seeds of wild barely (Hordeum spontaneum Koch.) were treated to germinate. Then, 8 seedlings were planted within each 3-L pot and grown in the Research Greenhouse of Bu-Ali Sina University, Hamedan, Iran. At the four-leaf stage, they were treated with 0, 6.25, 12.5, 25, 50, and 100 g cycloxydim ha-1 using 3 nozzle types (i.e. Standard, Anti-Drift, and Air Induction), at 3 orifice numbers (i.e. single, twin, and Triplet) and 3 nozzle sizes (i.e. 11002, 11003, and 11004). The treatments were sprayed at a pressure of 300 kPa when the wind speed was less than 0.4 m s-1. The volume of spray created by 11002, 11003, and 11004 nozzle sizes was 160, 240 and 320 L ha-1, respectively. Three weeks after spraying, the dry weight of plants was determined. The date were fitted using a four-parameter log-logistic model to estimate the dose required to achieve 50% wild barley control (ED50).
Results and Discussion: The ED50 was significantly affected by the type, size, and orifice number of nozzle. In all types of nozzles (Standard, anti-Drift and Air Induction) and sizes (11002, 11003 and 11004), an increase in orifice number significantly reduced the values of ED50 for cycloxydim against wild barely, indicating increased efficiency of herbicide. This can be explained by two reasons. Firstly, with an increase in orifice number in each type of nozzles, the size of spray droplets decreases. Previous studies have proven that there is a negative relationship between the amount of spray droplets deposited on the target surface and the size of spray droplets. Therefore, by decreasing the size of spray droplets, they can be deposited more on the target surface, resulting in an improvement in the foliage-herbicides efficiency. Secondly, increasing the orifice number of nozzle can lead to the penetration of spray droplets into the canopy. Among the nozzles of 11002 in any orifice number, the performance of nozzles was ranked as Standard > Anti-Drift > Air Induction. However, among the nozzles of 11003 or 11004 in any orifice number, the performance of nozzles was as Standard = Anti-Drift > Air Induction. Among all types of nozzles in any orifice number, increasing spray volume from 160 to 240 L ha-1 reduced the ED50. However, only in the types of nozzles of Air Induction in any orifice number, increasing spray volume from 240 to 320 L ha-1 reduced the ED50.
Conclusion: It can be recommended that the most suitable nozzle for the application of cycloxydim against wild barely at a wind speed of less than 0.4 m s-1 with the aim of optimizing simultaneously both the dose of herbicide and the consumption of water is "Triplet Standard Flat Fan Nozzle 11003 " (spray volume= 240 L ha1).