# Influence of Vegetation Filter Strip on Slope Runoff, Sediment Yield and Nutrient Loss
## 3 Results
### The Effects of the VFS on Nutrient Loss
#### 3.2.2 The Effects of the VFS on TN Loss
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \multirow{2}{*}{**V Vegetation Coverage Type**} & \multirow{2}{*}{
\begin{tabular}{c} **Rainfall** \\ **Intensity** \\ **(mm/h)** \\ \end{tabular} } & \multicolumn{4}{c}{**TP in Runoff (mg)**} & \multicolumn{4}{c}{**TP in Sediment (g)**} & \multicolumn{4}{c}{**TN in Runoff (mg)**} & \multicolumn{4}{c}{**TN in Sediment (g)**} \\ \cline{3-14}  & & \multicolumn{4}{c}{**Slope (\({}^{\circ}\))**} & \multicolumn{4}{c}{**Slope (\({}^{\circ}\))**} & \multicolumn{4}{c}{**Slope (\({}^{\circ}\))**} & \multicolumn{4}{c}{**Slope (\({}^{\circ}\))**} \\ \cline{3-14}  & **5** & **20** & **35** & **5** & **20** & **35** & **5** & **20** & **35** & **5** & **20** & **35** \\ \hline \multirow{4}{*}{L} & 30 & 1.017 & 4.978 & 6.450 & 0.002 & 0.009 & 0.029 & 99.279 & 226.009 & 245.110 & 0.004 & 0.004 & 0.004 \\  & 60 & 8.475 & 15.503 & 18.332 & 0.012 & 0.051 & 0.071 & 308.764 & 339.164 & 362.296 & 0.011 & 0.011 & 0.011 \\  & 90 & 30.438 & 37.812 & 42.738 & 0.074 & 0.299 & 0.624 & 499.226 & 721.918 & 765.869 & 0.023 & 0.023 & 0.023 \\ \hline \multirow{4}{*}{Z} & 30 & 0.469 & 1.640 & 2.978 & 0.001 & 0.004 & 0.018 & 59.306 & 99.326 & 110.360 & 0.023 & 0.023 & 0.023 \\  & 60 & 4.049 & 9.538 & 13.878 & 0.008 & 0.028 & 0.029 & 198.789 & 271.852 & 272.594 & 0.090 & 0.090 & 0.090 \\  & 90 & 8.984 & 17.377 & 25.208 & 0.027 & 0.131 & 0.250 & 197.454 & 320.725 & 483.819 & 0.108 & 0.108 \\ \hline \multirow{4}{*}{Z\({}^{\prime}\)} & 30 & 0.577 & 1.277 & 1.304 & 0.001 & 0.004 & 0.022 & 43.015 & 119.691 & 128.178 & 0.169 & 0.169 & 0.169 \\  & 60 & 5.500 & 8.608 & 9.463 & 0.007 & 0.028 & 0.030 & 182.819 & 208.062 & 257.174 & 0.681 & 0.681 & 0.681 \\ \cline{1-1}  & 90 & 8.307 & 19.405 & 24.234 & 0.026 & 0.144 & 0.196 & 159.286 & 379.565 & 471.516 & 1.040 & 1.040 & 1.040 \\ \hline \end{tabular} Note: L stands for bare slope; Z stands for VFS1; and Z\({}^{\prime}\) stands for VFS2.  
\end{table} 
Table 2: Total loss of TN and TP in runoff and sediment under different combinations of factors. with the increase of slope and rainfall intensity, the effect of VFS on reducing nutrient (TN and TP) loss in sediment was gradually significant. When the rainfall intensity was 30 mm/h, VFS1 with a slope gradient of 5\({}^{\circ}\)or 35\({}^{\circ}\) was more effective in reducing the loss of TN in sediment. Furthermore, the two setting modes of VFS were suitable on a slope of 20\({}^{\circ}\) similarly. As the rainfall intensity was 60 mm/h, for a slope of 5\({}^{\circ}\), the two types of VFSs had similar effects on reducing the TN content in sediment. Plant can absorb and utilize mainly inorganic nitrogen, and the trunk and root system after vegetation wider is one of the main sources of organic nitrogen. However, when the slope gradient increased to 20\({}^{\circ}\) or 35\({}^{\circ}\), the TN loss of VFS1 was reduced by 6% and 10% more than that of VFS2. For a 5\({}^{\circ}\) slope with rainfall intensity of 90 mm/h, we can also reach a consistent conclusion: VFS1 was more effective. However, when the rainfall intensity remained unchanged at 90 mm/h and the slope increased to 20\({}^{\circ}\) and 35\({}^{\circ}\), under the condition that the width was fixed, the way of laying VFS2 was more conducive to reducing TN loss in sediment. In most cases, setting VFS1 can effectively reduce TN loss in sediment.