Determining the best ISUM (Improved stock unearthing Method) sampling point number to model long-term soil transport and micro-topographical changes in vineyards

Abstract

Advances in soil erosion measuring tools and micro-topography modelling will contribute to our understanding of land degradation processes and help to design correct erosion mitigation measures in agricultural fields. Vineyards being one of the most degraded agricultural landscapes, it is necessary to accurately predict soil erosion levels within them. One possible method to achieve this goal in vine plantations is ISUM (improved stock unearthing method). To apply ISUM, it is necessary to detect the graft unions, which are recognised as passive bioindicators of the original micro-topography at the time of planting. In this paper, we propose a methodology to determine: i) how many measuring points are necessary to reach the best estimate of soil erosion for developing current soil surface level maps; and ii) which spatial interpolation method is the best to map the microtopographical changes. ISUM was applied in the Ruwer-Mosel valley vineyards (Germany) using up to 18 measuring points at 10 cm intervals between opposite pair graft unions of the inter-row vine areas. Several interpolation methods were used to map the micro-topography changes and anisotropic ordinary kriging (OK) emerged as the best as judged by the performance statistics of the coefficient of determination and the rootmean-square-error. Our findings demonstrated that soil erosion rates were 40.1, 39.4, 25.0, 38.9, 37.9, to 64.8 Mg ha-1 yr-1 over the 40 years since the establishment of the vineyard studied, when using 18, 15, 10, 7, 5 and 2 measuring points, respectively. We propose that ISUM can be standardised as using measuring points at 10 cm intervals.

Applying the RUSLE and ISUM in the Tierra de Barros Vineyards (Extremadura, Spain) to Estimate Soil Mobilisation Rates

“…In another work, the rates of erosion appear conditioned by the source of material which reached an erosion rate of −87.7 Mg ha −1 yr −1 in lands dominated by loams in an 8-year old vineyard [54]. However, the differences are reduced if we compare our results with those of Rodrigo-Comino et al [40], in which different numbers of measurements were compared, and the erosion rates for 18 points were −40.1 Mg ha −1 yr −1 . The high soil erosion rates observed in this study requires that policymakers, farmers, and companies involved in wine production develop erosion control strategies to achieve environmental sustainability.…”

“…It is confirmed that the key factor for obtaining the best resolution in the generation of the final model depends on the number of measurements [40]. Therefore, in this study, measurements were carried out every 10 cm by the same person.…”

“…In this work, 29 measurements were taken between each opposite paired-vine, resulting in a total of 2871 measurements along the 99 opposite paired vine rows ( Figure 2C-F). In this way, greater accuracy can be obtained [40] than in measurements recorded in previous works [36] where parts of the surface between the rows were not measured.…”

Estimating Non-Sustainable Soil Erosion Rates in the Tierra de Barros Vineyards (Extremadura, Spain) Using an ISUM Update

“…After finding the graft union in each paired-vine, a meter tape was stretched between them to take measures each 10 cm (Figure 2e,f). In this investigation, a total of 28 measures were performed (two in each graft union and 26 in the inter-row area), obtaining a greater accuracy than in previous works where part of the surface between rows was not measured [41]. A total of 5904 points were measured using four rows and three inter-rows ( Figure 2g).…”

“…There are three areas that need to be improved in order to increase the scientific knowledge of soil erosion in vineyards: (i) the accuracy of the measures; (ii) the standardization of the protocols; and, (iii) an increase of the measurements reaching the most relevant viticultural areas of the world. Accurate measures in soil erosion investigations depend on different factors, such as the size of the plot [34,35], design of the plot [36], device used [37], factors [38,39], seasonal changes [40], or the number of repetitions or points to be measured [41]. They are well-known constraints of carrying out the same method in different regions because of economic costs, logistic issues, and agreement among research groups.…”