Improving stock unearthing method to measure soil erosion rates in vineyards

Vineyard soils experience high erosion rates compared to soils from other agricultural land uses. The high soil losses in vineyards limits the sustainability of traditional production schemes and warrants comprehensive research aimed at thwarting the main erosion processes affecting vineyard systems. However, long-term measurements, which include spatial variability of soil erosion rates at the plot scale, are uncommon, as most of the measurements have taken place either at the hillslope or watershed scales. Against this background, the stock unearthing method (SUM) can be considered a useful methodology. However, the current method falls short because it assumes that the topography between the vine lines (inter-rows) remains planar. Therefore, we propose a new methodology (ISUM: improved stock unearthing method) that includes three measurements between in the inter-row areas. By taking inter-row measurements, we hypothesized that the spatial patterns of sediment detachment, transport and deposition features in the inter-rows would be detected. The ISUM costs 20% more time to conduct than the SUM, but greatly improved the utility of the field survey. ISUM allowed for: i) the creation of maps that identified linear soil erosion features and accumulation sites; ii) measures the amount of soil accumulated under the vines; iii) estimation of soil erosion rates with higher accuracy at long-term periods in a specific moment. This study compared the ISUM with the SUM in a vineyard in Spain. Soil erosion rates with ISUM were -2.5 Mg ha yr(-1) while the SUM calculated rates of + 4.9 Mg ha yr(-1). Results showed that the traditional method underestimated soil rates a - 25.7%. Maps created with the ISUM technique could also be used to provide insights about sediment connectivity.