## 4 Discussion  
Herbicides to be effective need advantageous weather conditions. Active ingredients must be translocated from the leaf surface to the target site, which takes place during active weed growth [3], the intensity of which is also related to the course of weather conditions [15]. Higher temperatures are generally favored for faster biochemical processes but warmer temperatures also can reduce the uptake of herbicides. The optimum temperature for herbicide action is between 10-20 and 25 \({}^{\circ}\)C, because under these conditions the physiological processes of both the crop and the weeds are at their optimum level [9]. The action of herbicides is favored not only by moderate temperature but also high humidity (at least 60-70%) [16], because of better wetting of plants [17], increased retention [18], and reduced evaporation of droplets [19]. The uptake and high efficacy of herbicides are more dependent on the humidity of the air after application than during. Other factors, such as light, rainfall, relative humidity, moisture, and wind affect herbicide activity [20]. The temperatures at REC Zlotnik during herbicide application in each year of the study were favorable for herbicide activity, as the temperature did not fall below 15 \({}^{\circ}\)C during the treatments, with the exception of the second treatment in 2019--12.0 \({}^{\circ}\)C. It was also not higher than 20 \({}^{\circ}\)C, with an air humidity of 58%, but most often between 60 and 80%. However, assuming that favorable conditions for herbicide activity are temperatures between 10 and 20 \({}^{\circ}\)C [16] and air humidity over 60%, it can be assumed that thermal conditions were not  
Figure 3: Impact of adjuvants (EXP 1, EXP 2, EXP 3, AtB, and S) on the efficacy of a mixture of phenmendipham, ethofumesate and metamitron (FEM). FEM 1—200 + 200 + 700 g ha\({}^{-1}\); FEM 2—140 + 140 + 700 g ha\({}^{-1}\); EXP 1, EXP 2, EXP 3, AtB at 1.5 L ha\({}^{-1}\), S—0.1% \(v\)\(v\)\(v^{-1}\). Values in the columns marked with the same letter do not differ significantly according to the [PERSON] post hoc test at \(p\) = 0.05. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline  & \multicolumn{2}{c}{**pH**} & \multicolumn{2}{c}{**ST**} & \multicolumn{2}{c}{**CA**} \\ \hline  & **2017** & **2018** & **2019** & **2017** & **2018** & **2019** & **2017** & **2018** & **2019** \\ \hline Efficacy 2017 & 0.2452 & - & - & \(-0.5973\)* & - & - & \(-0.6748\)* & - & - \\ Efficacy 2018 & - & 0.3495 & - & - & \(-0.3726\) & - & - & \(-0.4122\)* & - \\ Efficacy 2019 & - & - & - & \(0.0499\) & - & - & \(-0.4412\)* & - & - & \(-0.4074\)* \\ \hline \end{tabular}
* Significant at \(p\) = 0.05; pH—reaction; ST—surface tension; CA—contact angle.  
\end{table} 
Table 5: The correlation coefficients between the physical and chemical properties of spray liquid and efficacy of FEM. the worst in this case either, as were the average daily air temperatures in the following several days after treatment. The EXP 1, EXP 2, EXP 3, and standard adjuvants AtB and S increased the pH of the spray liquid containing phenmedipham, ethofumesate, and metamitron relative to the untreated check. However, according to numerous studies [21; 22; 23], their solubility varies (1.8-4.7; 50 and 1700 mg L\({}^{-1}\), respectively), but does not depend on the spray liquid pH. In our own study, the impact of adjuvants on ST and CA depended on the formulation of the product to which it was added, with the direction of change always being the same; that is, adjuvants reduced the ST and CA of the spray droplets. Only the magnitude of these changes differed. The ST and CA of spray droplets containing FEM, irrespective of the agent rate, were moderate, reduced to 30-40 mN m and 58-69\({}^{\circ}\). According to [24], adjuvants, regardless of chemical composition, reduced ST and CA of droplets but even in the value range of 30-40 mN m\({}^{-1}\), it does not necessarily transfer into high herbicide efficacy [25].