# The Impact of Incorporated Nonwovens on the Surface Roughness of Sport Pitches
## 4 Discussion  
In this section, the results are analyzed and discussed. Three sensors were compared during the experiment. The feeler wheel showed the lowest standard deviation and a significant difference after incorporating the nonwoven. These results indicate that the feeler wheel is best suited to determine the effects of the incorporation device in relation to the surface. The feeler wheel weighs 6100 g and therefore avoids measurement errors due to vegetation because it presses down the grass leaves. However, the weight is low enough that no compaction of the soil surface occurs. This fact is evident from the significant difference between the treatments. The measurements of the ultrasonic and long-range sensors showed no significant difference and a high standard deviation. In particular, the long-range sensor showed high scattering in the values measured on the first plot (Figure 5). The reason for this could be that the leaf mass of the grasses deflects the laser beam. This ultrasonic sensor had already been tested to measure the working quality of tillage implements such as the chisel plow [19]. The circular measurement area of the ultrasonic sensor has a suitable size. However, a soil surface is significantly rougher than the tested sports surface. Still, a significant increase in the sports turf surface is evident as a result of the incorporation process. This is mainly due to the opening of the soil with the aid of the colter, which pushes the soil open and cannot be completely leveled by the pressure rollers. In the same way, the cutting of the turf cover has an influence on the surface change.  
The measured profiles were compared to the \(RMS_{roughness}\). Considering the measurement results of the feeler wheel, it is evident that there is a significant increase in roughness. The question now arises as to how this change is to be assessed. In the German standard DIN 18035-4, a maximum deviation of 30 mm at 4 m measuring bar length is specified. Since this deviation is only measured at one point, the \(RMS_{roughness}\) according to Equation (2) is equal to the root of 30 mm. The maximum roughness is about 5.4 mm. According to the results measured before the incorporation, the roughness is higher than the standard. However, the difficulty is the comparability of the two measuring methods. In addition, the vegetation causes high roughness due to the uneven height of the material build-up caused by the turf (e.g., by lawn thatch [20]). To solve this problem, the turf could have been groomed and top-dressed before the trials started. However, to investigate the influence of the device incorporating the nonwoven, the difference between before and  
Figure 8: Arithmetic mean \(RMS_{roughness}\) (m) of the measured profile before and after the incorporation of the nonwoven. The measurement was performed by ultrasonic sensor. The error bar shows the standard deviation. \(n=14\). The \(p\)-value shows the paired Tukey test for mean \(RMS_{roughness}\) before and after the incorporation calculated for all three plots.  
after installation is crucial. If comparing the results of the feeler wheel, the difference is significant, but it is less than 5 mm. This indicates that the developed device increases the roughness of the surface. The measurement results indicate that it is necessary to improve the incorporation device and, for example, to equip it with a heavy pressure roller.