Remote sensing of soil ridge height to visualize windbreak effectiveness in wind erosion control: A strategy for sustainable agriculture

Tree windbreaks have multifunctional benefits including wind damage reduction, soil erosion control, and biodiversity conservation. The removal and low adoption of tree windbreaks due to agricultural expansion are issues in many regions despite their critical role in improving agricultural sustainability. Farmers' and landowners' recognition of the benefits of windbreaks in their cultivation environments is necessary to preserve windbreaks. To visualize the benefits of windbreaks using remote sensing techniques, we focused on the top-tobottom height of soil ridges, which are created homogeneously throughout the field using a machine. In this paper, we propose the use of soil ridge height as a remote sensing indicator to evaluate the spatial distribution of wind erosion. We tested two different remote sensing approaches at a potato field: one was an unmanned aerial vehicle (UAV) and the other was an Apple iPad Pro with a built-in light detection and ranging (LiDAR) sensor. Based on geographic information systems (GIS), the digital elevation model (DEM) was divided into grids with one ridge-furrow pair, with the ridge height given by the difference between the maximum and the minimum elevations in each grid element. The grid-based analysis of the differences in ridge heights between two periods was less affected by the positioning error than the DEM of difference. In a year with large erosion of up to 0.07 m, the spatial pattern of the wind erosion was identified from a single post-erosion survey. Structure-from-motion (SfM) and multiview stereo (MVS) photogrammetry from real-time kinematic-UAV identified smaller wind erosion in an area sheltered by the windbreak and just leeward of a grass-covered road. The iPad LiDAR exhibited higher accuracy in reproducing the ridge height than UAV-SfM-MVS and successfully visualized the windbreak effects by scanning plots at different distances from the windbreak. The iPad LiDAR system is considerably less expensive than UAV-SfM-MVS. In addition, compared to UAV techniques, it is easier to create DEMs with the iPad LiDAR system. Thus, this technique would be beneficial for the spatial evaluation of wind erosion in various fields with different site conditions. This approach is also expected to contribute to the effective visualization of windbreak benefits through three-dimensional printing of DEMs. It provides rapid and innovative method to send a clear message to stakeholders about the importance of windbreaks. To extend smart device applications to remote sensing, our findings emphasize the importance of devising measurement targets to improve detectability and simplify survey designs.