## 4 Conclusions  
In the analyzed configuration of nozzles and diffusers, air-assisted spraying improved liquid deposition in the proximity of the axes of hollow-cone nozzles, indicating that they could effectively be used in over-row sprayers when applied chemicals have to be directed onto plant rows and where air and liquid streams are required to penetrate all plant segments, including their lower parts.  
The airflow velocity along the width of the sprayer boom at both fan-speed settings was determined by the boom height above the ground and the diffuser spacing. The uniformity of the air velocity distribution could be improved by positioning the diffusers at 60 cm intervals when the boom height was around 30 cm or at 80 cm and 90 cm intervals when the boom height was around 30-40 cm. However, due to the difference between the  
Figure 6: Comparison of horizontal spray distribution in variant I with the boom positioned 50 cm above the patternator and one flat-fan nozzle positioned along the diffuser axis: (**a**) without the secondary air blower; (**b**) with the secondary air blower and the fan operating in first gear; (**c**) with the secondary air blower and the fan operating in second gear.  
minimum and maximum airflow velocities, optimal results were achieved when the boom as positioned 50 cm above the crop stand.  
In the three analyzed scenarios, the uniformity of the horizontal spray distribution was optimized when the nozzles and diffusers were spaced 80 cm apart. In this variant, the values of the coefficient of non-uniformity and the \(CV\) of the horizontal spray distribution generally decreased. The difference relative to the entire width of the boom with differently spaced nozzles reached 60%.  
No significant differences in the analyzed coefficients were observed when the diffusers were connected to one or two nozzles. The \(CV\) of the horizontal spray distribution was lower in the variant where two nozzles were positioned at a distance of 9 cm from the diffuser's axis of symmetry. In turn, the value of the coefficient of non-uniformity improved when each diffuser was connected to a single nozzle installed in the diffuser's axis of symmetry. The difference between the above variants ranged from around 3% to around 22%.  
If the interval between nozzles has to be increased above the recommended value of 50 cm, hollow-cone nozzles should be used instead of flat-fan cones, despite the fact that the former have a smaller spray-cone angle. When an SAB is not activated and when nozzles are spaced 80 cm apart, spray treatments can also effectively be applied to close-grown crops because the mean values of the coefficient of non-uniformity and the \(CV\) of the horizontal spray distribution did not exceed 10% in this scenario.  
Conceptualization, P.M. and A.L.; methodology, P.M. and A.L.; software, P.M.; validation, Z.K.; formal analysis, Z.K. and S.L.; investigation, A.L.; resources, A.L.; data curation, P.M. and A.L.; writing--original draft preparation, P.M. and Z.K.; writing--review and editing, P.M., Z.K., A.L., S.L., P.B. and V.M.; visualization, Z.K.; supervision, P.M., Z.K., A.L. and P.B.; project administration, A.L.; funding acquisition, A.L. All authors have read and agreed to the published version of the manuscript.  
The presented research was funded by the Polish National Center for Research and Development (NCBR) within the framework of the project entitled \"A family of field sprayers with an air sleeve\" (No. MAZOWSEZ/0002/19).  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.