Multi-temporal analysis to asses different conservative cultural management on erosion processes in steep-slope agriculture through remote sensing techniques

Nowadays, agricultural cultivation in steep slope areas represents an additional challenge against global climate change. Due to increased rainfall intensity and their complex geomorphology, steep-slope vineyards are also strongly affected by erosion processes. Finding solutions to mitigate this problem is a priority to ensure sustainable production. A widely used conservation approach against erosion involves maintaining an organic soil cover through herbs, mulching, or reusing crop residues. Conversely, tillage and weed removal can accelerate soil erosion in steep slope areas and influence their micro-topography by altering soil surface roughness and sediment connectivity. The latter, useful to identify the surface portions that are most connected and prone to more significant erosion, has often been neglected in past soil erosion studies but needs to be considered to effectively define the sediment surface contributing to estimates of erosion processes. Remote Sensing techniques (e.g., digital photogrammetry with Structure from Motion-SfM, Light Detection and Ranging-LiDAR technology) have recently provided new opportunities for surveying erosion processes, especially by exploiting Unmanned Aircraft Systems (UAS) that can also mount multispectral cameras as payloads, which, integrated with topographic data, can provide helpful information for analyzing the status of crops. This research carries out a multi-temporal analysis of sediment connectivity following management changes in the row and vineyard inter-row cover to assess the effects on erosion processes using Digital Elevation Models (DEMs) provided by LiDAR and SfM surveys with UAS. All maps were generated with a centimetric resolution to capture the micro-topographic features. The study vineyard (1943 m²) is located in a steep slope area (ca. 18%) in the municipality of Betanzos (43° 15' 56.20" N; 8° 12' 1.32" W; Coruña, Spain) under a temperate oceanic climate and managed according to organic farming practices, without any irrigation system.

In 2021, all rows and inter-row areas had covered with resident vegetation. In 2022, three treatments were carried out in the inter-row areas (i.e., mixed seeding cover, massive straw mulching, and cover by resident vegetation), while all the rows were covered with jute agro-textile. Eight topographic surveys (i.e., SfM with RGB and multi-spectral camera and LiDAR by UAS) were carried out in the study area from March 2021 to November 2022. The multi-temporal DEMs were used to derive multi-temporal maps of sediment connectivity indices (IC), Differences of IC (DoIC), and DEM of Differences (DoDs) to calculate vegetation volumes and estimate net soil loss and deposition rates over time. Subsequently, the geomorphological information was correlated with the multi-spectral surveys by making orthomosaics and calculating vegetation indices (e.g., NDVI, NDRE) that allowed the assessment of the land cover condition as a result of changes in cultural management of vineyard rows and inter-rows. The preliminary results show how the information obtained from the extensive database created (i.e., DEMs, DoDs, CI and DoIC maps, vegetation indices) is very useful in assessing the effectiveness of the conservation cultivation approaches used, identifying the portions of soil potentially more prone to erosive processes to provide a useful planning tool for stakeholders for sustainable vineyard management.