Spain is one of the largest wine producers in the world, with Extremadura (south-west Spain) being its second-largest producing region after Castilla La Mancha. Within Extremadura, the most traditional and productive viticulture region is the Tierra de Barros, which boasts an annual production of 3×106 litres. However, no soil erosion assessment has been undertaken in any vineyard in the region to ascertain environmental sustainability. Therefore, the Improved Stock Unearthing Method (ISUM) and the Revised Universal Soil Loss Equation (RUSLE) were applied to assess the long-term soil erosion rates. Both methods were applied using an experimental plot (2.8 m × 148.5 m) encompassing 99 paired vines in a 20-year-old vineyard under a tillage management system and on bare soils throughout the year. The ISUM and RUSLE found total soil mobilization values of 45.7 Mg ha−1 yr−1 and 17.4 Mg ha−1 yr−1, respectively, a difference of about 5 times. Mapping techniques showed that soil surface declined to an average of −6.2 cm, with maximum values of −28 cm. The highest values of soil depletion were mainly observed in the upper part and the form of linear features following the hillslope direction. On the other hand, under the vines, the soil surface level showed accumulations of up to +2.37 cm due to tillage practices. Our study demonstrated the potential of high soil erosion rates occurring in conventional vineyards managed with tillage in the inter-row areas and herbicides under the vines within the Tierra de Barros. Also, we demonstrated the elevated differences in soil mobilisation rates using the ISUM and RUSLE. Therefore, further research must be conducted in other vineyards to determine the suitability of the models for assessing soil erosion rates. Undoubtedly, soil conservation measures must be designed and applied immediately due to high erosion rates.
Water is a key strategic resource, particularly in Mediterranean climate-type areas with impermeable rocks and shallow soils like Southwestern Spain. The region of Extremadura is commonly known by its large surface occupied by big dams (30% of water dammed in Spain) although this theoretical abundance of water does not hide other problems of use. In this study, we have interviewed 132 people from the municipality of Arroyo de San Serván in order to know what the problems related to water use are, especially those that concern local people the most. Regarding the use of water at home, 90% of interviewees spend less than 60 EUR per month for water and their mean degree of satisfaction about the service is 3.7 out of 7. The reason for this low value can be the excessive content of calcium and bad taste according to 82.1%. Therefore, 64.2% of people do not usually drink water from the tap. Around two thirds of these local people usually buy water in the supermarket or drink filtered water. Concerning agricultural activities, local people gave great importance to irrigation as a source of employment (5.6/7) and inputs (4.5/7), although their satisfaction decreases about the current price of water for agriculture (0.02 EUR m−3). In addition, they are really worried about the overuse of fertilizers and herbicides (5.4/7) and they think about the necessity of taking measures to reduce these problems (6.1/7) as well as to reduce some management problems such as supply cuts. In the last few years, private (swimming pools) and public leisure facilities (swimming pool and spa) have been built in spite of not being considered important by local people (3.6–4.0/7). Nevertheless, about 60% of them consider these common facilities very positive in terms of employment, tourism attractions and entertainment for local people.
Monitoring soil erosion processes and measuring soil and water yields allow supplying key information to achieve land degradation neutrality challenges. Vineyards are one of the most affected agricultural territories by soil erosion due to human and natural factors. However, the spatial variability of soil erosion, the number of sampling points, and plot size necessary to estimate accurate soil erosion rates remains unclear. In this research, we determine how many inter-rows should be surveyed to estimate the soil mobilization rates in the viticulture area of Tierra de Barros (Extremadura, SW Spain) using the Improved Stock Unearthing Method (ISUM). This method uses the graft union of the vines as a passive biomarker of the soil surface level changes since the time of plantation and inter-row measures. ISUM was applied to three inter-row and four rows of vines (5904 sampling points) in order to determine how many surfaces and transects must be surveyed as all the previous surveys were done with only one inter-row. The results showed average values of soil depletion reaching −11.4, −11.8, and −11.5 cm for the inter-rows 1, 2, and 3, respectively. The current soil surface level descended 11.6 cm in 20 years. The inter-rows 1, 2, and 3 with a total area of 302.4 m 2 each one (2016 points) recorded 71.4, 70.8, and 74.0 Mg ha −1 yr −1 , respectively. With the maximum number of sampling points (5904), 71.2 Mg ha −1 yr −1 were obtained. The spatial variability of the soil erosion was shown to be very small, with no statistically significant differences among inter-rows. This could be due to the effect of the soil profile homogenization as a consequence of the intense tillage. This research shows the potential predictability of ISUM in order to give an overall overview of the soil erosion process for vineyards that follow the same soil management system. We conclude that measuring one inter-row is enough to get an overview of soil erosion processes in vineyards when the vines are under the same intense tillage management and topographical conditions. Moreover, we demonstrated the high erosion rates in a vineyard within the viticultural region of the Tierra de Barros, which could be representative for similar vineyards with similar topographical conditions, soil properties, and a possible non-sustainable soil management system.
The drawing of maps of soil quality at a large scale is increasingly being more useful to land planners and stakeholders. Nevertheless, it involves different methodological steps from the description of soil profiles in the field until the regional mapping of integrative soil quality index (IQI) values. The development of proper scoring functions is a paramount task for the calculation of these IQI values since every parameter needs to be standardized accordingly and weighting factors are usually estimated by multivariate techniques. The main goal of this study was to map soil quality in the Spanish region of Extremadura (commonly known by its rangelands called dehesas). To do that, i) we gathered information from 194 soil profiles described throughout the region, ii) we calculated the weighting factors of ten meaningful parameters used as indicators by using multivariate techniques (Principal Component Analysis, PCA; and Analytic Hierarchy Process, AHP), and iii) we developed standard scoring functions (SSFs) that represent the singularity of every variable (less is better, more is better). We established upper and lower limits for standardizing the values of each indicator properly. Regarding weighting factors, soil texture was highlighted by the PCA and nutrients by the AHP. Once IQI values were calculated, two regional maps of soil quality were drawn by using interpolation methods (ordinary kriging). The IQI maps showed remarkable spatial differences in soil quality presumably induced by land management. We conclude this methodology could be useful and we encourage other colleagues to test its effectiveness in places where soil data are available.
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