## 1 Introduction  
The activity and selectivity of herbicides are affected by various factors, such as temperature, moisture, soil texture, weed biology, physiological, and biochemical processes [1; 2; 3], and thus, the amount of herbicides reaching weeds is actually a small percentage of the pesticides applied [4; 5]. It is, therefore, logical to enhance the application of pesticides to deliver more potent ingredients directly to the targeted weeds, thereby enabling the application of the smallest possible dose of herbicide. To maintain the great efficacy of herbicide applied at reduced rates, adding an adjuvant to the spray liquid containing herbicides has been suggested [6]. Water can also influence the activity of herbicides; therefore, the final weed control result depends on its quality, i.e., primarily its reaction, temperature, and hardness [7; 8]. Furthermore, numerous factors contribute to the effectiveness of herbicides, such as the choice of herbicide, application rate and timing, application method, pH of spray liquid, and technique [9]. Multifunctional adjuvants, also known as multifunctional or multicomponent, are characterized by a wide range of action. They can affect both the retention and absorption of spray droplets. In addition, adjuvants neutralize the negative effect of mineral salts contained in spray liquid [10]. Activator adjuvants can include surfactants, as well as oils, pH buffers, or nitrogen-based fertilizers. Their presence in a single formulation allows them to be used with more herbicides due to the elimination of the specific action of the individual adjuvants included in its formulation. Multifunctional adjuvants, similar to multi-component herbicides, are easier to use as they eliminate the need to purchase and mix individual components. Adjuvants added to the spray liquid with herbicides facilitate the penetration of herbicides into the leaf and cells [11]. However,only an appropriate adjuvant for a particular herbicide (active ingredient) enhances the herbicide's performance, while the wrong one may even reduce its efficacy [12].  
Effective weed control is particularly important for widely spaced crops, where post-emergence dicotyledonous weed control is mainly based on the use of substances such as ethofumesate, phenmedipham, metamitron or chloridazon, clopyralid, and triflusulfuron-methyl [13]. Considering both external factors and herbicide formulations, selecting the right adjuvant is difficult, especially for a single-component adjuvant.  
The research hypothesis was that herbicide performance depended on a number of factors, which can only be overcome if a multifunctional adjuvant is added to the spray liquid. It should, therefore, be assumed that to achieve great efficacy, limit costs, and reduce adverse effects on the environment, the addition of effective adjuvarts with a multidirectional effect, appropriately selected for the herbicide in question, is essential. It is then possible to effectively control weeds, but with reduced doses of herbicides because the production of the tested multifunctional adjuvarts is cheaper, and they are non-crystallizing, compatible, and keep the environment safer due to the reduction of active substances of pesticides reaching the field.  
The research purpose was to assess the effects of tested multifunctional adjuvarts on the reaction, contact angle, surface tension, and electrolytic conductivity of the spray liquid droplets, as well as on the herbicidal efficacy of sugar beet crop plants of herbicides containing phenmedipham, ethofumesate, and metamitron.