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Most field erosion studies in agricultural areas provide little information on the probable errors involved. Here, for the first time, we compare the accuracy, time and cost of conventional and new methodologies for gully surveying, and provide a model to estimate the effort required to achieve a specified accuracy. Using a terrestrial LiDAR survey of a 7.1-m-long guliy reach as a benchmark data set, the accuracies of different measurement methods (a new 3D photo-reconstruction technique, total station, laser profilemeter, and pole) are assessed for estimating gully erosion at a reach scale. Based on further field measurements performed over nine gullies (>100 m long), a simulation approach is derived to model the expected volume errors when 2D methods are used at the gully scale. All gullies considered were located near Cordoba, Spain. At the reach scale, the field measurements using 3D photo-reconstruction and total station techniques produced cross-sectional area error values smaller than 4%, with other 2D methods exceeding 10%. For volume estimation, photo-reconstruction proved similar to LiDAR data, but 2D methods generated large negative volume error (E^) values (<-13% for laser profilemeter and pole). We show that the proposed error expressions derived from the model are in line with the reach-scale field results. A measurement distance factor (MDF) is defined that represents the ratio between cross-section distance and the gully length, and thus reflects relative survey effort. We calculate the required MDF for specified values of f^, illustrating how MDF decreases with increasing gully length and sinuosity.Abbreviations: A, cross sectional area (m^); D, distance between adjacent cross sections (m); DEM, digital elevation model; E^, relative area measurement error (%); E'-, relative length error (%); E^, relative volume measurement error (m-^); L, Gully length (m); i.g^,, distance between the extremes of the gully (m); i-gj-t-sm' distance between the extremes of a 5 m reach (m); L^, polyline length defined by cross section distance (m); /. ,, length of the polyline that fits coarsely the gully thalweg following knickpoints (m); ¿real-5m' real length of a 5 m reach (m); MDF, measurement distance factor (%); n, number of subreaches; N^^, total number of 5-m reaches within a gully; S^'^¡^^^¡, local sinousity; 5 II , gully sinuosity; SE, sinuosity factor; o^^ standard deviation of the volume error drstribution (%); V, volume of eroded soil within the gully (m^).

Small-scale portable rainfall simulators are an essential research tool for investigating the process dynamics of soil erosion and surface hydrology. There is no standardisation of rainfall simulation and such rainfall simulators differ in design, rainfall intensities, rain spectra and research questions, which impede drawing a meaningful comparison between results. Nevertheless, these data become progressively important for soil erosion assessment and therefore, the basis for decision-makers in application-oriented erosion protection.

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Is the cover crop practice suitable for soil and water conservation in olive tree cropping? Rainfall, runoff, sediments, nutrient and organic carbon losses from 8 x60-m plots were measured during four hydrological years (2002 to 2007) in a field trial, in which two different soil management systems were used to confirm this hypothesis: a cover crop, (CC), and conventional tillage, (CT). The plots were located in a private olive tree farm on a sandy-loam soil, near Seville, southern Spain. The cover crop, as compared to conventional tillage, efficiently reduced runoff and sediment yield down to tolerable levels, 5.68% of the rainfall being converted to runoff, and the soil loss reaching 0.04 kg m-2 year-1 , as the average of four years. Additionally, in the cover crop treatment, the values of the nutrient export either dissolved in the runoff water or adsorbed in the sediment, were lower than the analogous values of the conventional tillage treatment: 0.631 and 0.065 kg m-2 year-1 of organic carbon and nitrogen, respectively, 0.175 and 0.0333 kg m-2 year-1 of soluble K and P, respectively, and 0.010 and 0.002 kg m-2 year-1 of available K and P, 2 respectively. The adoption of a cover crop as a soil management practice can be a feasible way to reach sustainability in many olive-cropped soils of southern Spain, although this method is not always easy to implement due to technical problems such as seed selection, its maintenance, and the choice of the correct killing date to avoid water competition. These difficulties could explain the slow rate of its adoption by many farmers. Further exploration of these aspects is required, as well as a specific agricultural extension campaign.

At the global scale, vineyards are usually managed intensively to optimize wine production without considering possible negative impacts on biodiversity and ecosystem services (ES) such as high soil erosion rates, degradation of soil fertility or contamination of groundwater. Winegrowers regulate competition for water and nutrients between the vines and inter‐row vegetation by tilling, mulching and/or herbicide application. Strategies for more sustainable viticulture recommend maintaining vegetation cover in inter‐rows, however, there is a lack of knowledge as to what extent this less intensive inter‐row management affects biodiversity and associated ES.We performed a hierarchical meta‐analysis to quantify the effects of extensive vineyard inter‐row vegetation management in comparison to more intensive management (like soil tillage or herbicide use) on biodiversity and ES from 74 studies covering four continents and 13 wine‐producing countries.Overall, extensive vegetation management increased above‐ and below‐ground biodiversity and ecosystem service provision by 20% in comparison to intensive management. Organic management together with management without herbicides showed a stronger positive effect on ES and biodiversity provision than inter‐row soil tillage.Soil loss parameters showed the largest positive response to inter‐row vegetation cover. The second highest positive response was observed for biodiversity variables, followed by carbon sequestration, pest control and soil fertility. We found no trade‐off between grape yield and quality vs. biodiversity or other ES. Synthesis and applications. Our meta‐analysis concludes that vegetation cover in inter‐rows contributes to biodiversity conservation and provides multiple ecosystem services. However, in drier climates grape yield might decrease without irrigation and careful vegetation management. Agri‐environmental policies should therefore focus on granting subsidies for the establishment of locally adapted diverse vegetation cover in vineyard inter‐rows. Future studies should focus on analysing the combined effects of local vineyard management and landscape composition and advance research in wine‐growing regions in Asia and in the southern hemisphere.

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