BUSCADOR RECOLECTA

Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/ medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (Rcum) minimized the root mean square error. A linear fit for the estimation of Rcum in ungauged atchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, Rcum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations
of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical
and efficient to take action to mitigate runoff in rural locations., This research was supported by the
research projects CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R,
CGL2014-52135-C3-3-R, CGL2015-65569-R, CGL2014-56907-R, and
AGL2015-65036-C3-1 funded by the MINECO-FEDER (Spanish Ministry of
Economy and Competitiveness). E.N.-R. is the beneficiary of a Ramón y Cajal
postdoctoral contract (Spanish Ministry of Economy and Competitiveness).

Tree crops cover a large area of European landscape, 13.3 million hectares, with olive, grapes, nuts and almonds been the most extended and mostly concentrated in Mediterranean areas. The cultivation of tree crops in rain limited Mediterranean areas depend on an adequate management of water balance that, been historically mostly based on bare soil, has created severe erosion and offsite contamination problems. Temporary cover crops can be an alternative to control these problems with a larger effect on erosion control than on reducing runoff, and a moderate impact on soil properties. This impact depend strongly on the ability to implement temporary cover crops that achieve a significant development during the rainy season while simultaneously minimizing the competition for soil water with the major crop, which is not always easy in commercial farms. This balance between soil protection and yield has been achieved in some conditions but not in others, and a significant reduction in yield has been reported for some situations. This potential risk of yield decrease, combine with the difficulty to see a collapse in yield due to soil degradation by water erosion in the short/medium term can explain, partially, the reluctance of farmers for an extensive use of temporary cover crops. The development of improved strategies for using temporary cover crops which could include the use of water balance models, new varieties better adapted to the region, and strategies for restoring ground cover in severely degraded orchards seems to be necessary, coupled with regulations and incentive to their use by farmers. Future research should focus in the less understood elements of this system, among them root development, biomass production, phenology under different microclimate of the cover crops and the main tree crops, use of cover crops mixes, which are hampering the tuning of the system for specific conditions. It is also necessary a better definition and measurement of the impacts of cover crops on biodiversity that should be related to the landscape conditions., I would highlight specially
the contribution of projects AGL2015-65036-C3-1
and Vinedivers (Spanish Ministry of Economy
and Competitiveness), P12-AGR-931 (Andalusian
Government) and FEDER funds which are currently
funding research on this subject in the laboratory of
Soil Erosion at IAS-CSIC., Peer reviewed

This article belongs to the Special Issue Soil-Plant Interaction: Focus on Plant Growth and Soil Biodiversity., Cover crops can be an effective means to protect soil and reduce risks of erosion in olive groves. However, for this protection to be significant, the vegetation must attain a significant amount of ground cover, which is estimated to be at least 30% during the rainy season. In olive groves on degraded soils, which occupy large surface areas in the olive-growing areas of the Mediterranean region, the establishment of cover crops may be an arduous challenge, particularly in areas with a high density of rabbits. In this study, we have selected two olive orchards with scarce natural vegetation located in Andalusia (southern Spain), in which rabbit populations intensively forage the cover crops, to test whether the self-seeding of an unpalatable species corn chamomile (<i>Anthemis arvensis</i> L.; <i>A. arvensis</i> for short) could achieve sufficient coverage for soil protection, in the year following that in which the broadcast-seeding was carried out for the implementation of cover crops. The hand broadcast-seeding of <i>A. arvensis</i> was carried out on sixteen elementary plots in the lanes of the two olive orchards in the autumn of 2015, and seed germination in the subsequent self-seeding took place in the autumn of 2016. The plant height and <i>A. arvensis</i> ground cover in these plots were measured throughout the two growth cycles, and aerial biomass was measured at maturity. The results showed that there were no significant differences in the maximum plant height between the two growth cycles (mean ± SD of 21.2 ± 1.6 cm), while the ground cover was significantly greater in the case of self-seeding, especially during the winter (37.2 ± 8.1 and 9.3 ± 6.7% for self-seeding and broadcast-seeding, respectively), and aerial biomass at maturity had more than doubled (99.7 and 43.9 g m⁻², respectively). These data suggest that this unpalatable species could establish an effective herbaceous cover by means of self-seeding in olive groves on degraded soils that are being overgrazed owing to the high pressure of rabbits. Despite the poor establishment in the broadcast-seeding year, our findings indicate that <i>A. arvensis</i> might be an alternative cover crop that could help the sustainability of these threatened olive groves. Its high seed production (2000 to 4000 seeds per plant), and an early emergence just after the first autumn rains, should result in an increased ground cover by <i>A. arvensis</i> during the rainy season in the subsequent years of self-seeding. This, therefore, could contribute to soil conservation, in addition to providing other benefits of increased biodiversity and improvement for agricultural landscapes., This work was supported by the projects AGL2015-65036-C3-1-R of the Spanish Ministry of economy and competitiveness, P12-AGR-931 and EU–FEDER (Fondo Europeo de Desarrollo Regional) funds. AJC was funded by a FPI (formación de personal investigador) pre-doctoral scholarship provided by MINECO (Ministry of economy and competitiveness).

Trabajo desarrollado bajo la financiación del proyecto “Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping Systems” (773903), coordinado por José Alfonso Gómez Calero, investigador del Instituto de Agricultura Sostenible (IAS)., This manuscript presents a questionnaire-based study aimed to provide a detailed analysis on the different soil management carried out by olive farmers in two representative olive-growing areas in southern Spain (Cordoba and Estepa), their perceptions on cover crop use and the possible influence of the different types of farms and farmers’ typologies on these perceptions. Our results show a relatively large variability of soil management, with fourteen options, as a result of a combination of different alternatives for bare soil and cover crops with the use or not of pruning residues, but with a great similarity between both areas. The results indicate a high adoption of soil conservation measures in the two study areas, with 63% of farmers using cover crops and 80% a mulch of pruning residues, higher than that reported in previous studies in Southern Spain, and a trend of lower use of these techniques by less experienced and younger farmers. This high penetration of soil conservation measures resulted in a significant reduction of soil erosion risk, as indicated by the relatively low values for the cover and management factor (C) of RUSLE, also calculated and presented in this study, but also the possibility of focusing further efforts on farmers with less experience. Our results indicate the persistence of a minor, but relevant, percentage of farmers using bare soil management (37%) and no mulching (20%), with a moderate concern on the impact of soil erosion on soil degradation and provision of ecosystem services. This suggests the need to concentrate efforts also on this cluster of farmers to enhance the success of what seems to be a remarkable expansion of the use of soil conservation measures in recent decades in Southern Spain, but also in similar areas in the Mediterranean basin., This work was supported by P12-AGR-0931 (Andalusian Government), AGL2015-65036-C3-1-R and PID2019-105793RB-I00 (Spanish Government), SHui (European Commission Grant Agreement number: 773903) and EU-FEDER funds, as well as by the cooperative agreement between the DOP Estepa and the University of Cordoba. All this support is gratefully acknowledged., Peer reviewed

The sustainability of farming systems has been enhanced by legislation on different scales, but at the same time these policies also promote more productive systems through farming intensification (e.g., use of irrigation or high tree densities). This is the case of olive orchard expansion on cereal cropland in recent decades. This study analyses the impact of this expansion on orchard characteristics and landscape elements in a case study in the ’campiña‘ of Cordoba in Southern Spain based on the evolution of their surface and typologies during the period from 2005 to 2018. Our results show that olive orchards doubled their surface after the 13-year period, from 7997.8 to 16,447.6 ha. On average the new orchards tended to have higher plant density and a more frequent use of irrigation in the study period. Despite this trend towards intensification, the current situation shows a majority of rainfed (76.4%) and medium tree densities, 120–200 trees/ha, (42.7%) of the area. Nevertheless, newly intensified orchards are arising in the region, resulting in a mosaic of orchards of different characteristics (slope, tree density, soil type) and agricultural managements (irrigation, ground cover vegetation).

In addition, this characterization was complemented with an inventory of the existing semi-natural elements associated with these orchards to identify the current state of the regional agricultural landscape. A total number of 507 isolated trees and different linear and polygonal landscape elements (343.9 km and 714.0 ha, respectively), mainly segmented, were inventoried. From these polygonal landscape elements, a significant fraction (e.g., slopes, gullies, water banks and non-productive strips/faces) remains unvegetated (57%). Therefore, these elements must be considered in multiscale agricultural policies as potential restoration areas to enhance ecosystem service provisioning., This work was supported by AGL2015-65036-C3-1-R, PID2019-105793RB-I00 (Spanish Government), SCALE (European Commission Grant Agreement number: 862695) and Shui projects (European Commission Grant Agreement number: 773903) and EU-FEDER funds. Also, to the International Centre for Advanced Mediterranean Studies (CIHEAM) that supported A. Boumahdi’s master studies at the University of Cordoba, and whose main findings resulted in this manuscript.