Agricultural soil challenges in Spain: overcoming existing barriers for the implementation of sustainable practices
Spain has a great diversity of agricultural soils due to large variations in climate, geology, land uses, and crops. Soil loss is of particular concern in most of its territory, along with N-related pollution caused by inadequate farming procedures. Several sustainable practices have been proposed to tackle those challenges and public policies may help in overcoming existing barriers for their implementation.
Agricultural crops and pastures cover almost 50% of the Spanish territory. Large climatic variations support a great variety of agrosystems: Permanent pastures and maize prevail in northern Spain, while vineyards, olive- and almond-orchards, rainfed crops and dehesas (a traditional extensive agroforestry system where pastures and sparse trees co-exist) thrive in its Mediterranean areas. Horticulture and citrus crops are predominant under irrigation and temperate conditions, and maize is also irrigated in some locations. Subtropical fruit crops prevail in the Canary Islands. Soil conditions are also quite diverse, due to dissimilarities in geology, climate, land use, and agricultural crops and practices. For instance, soil organic carbon content is typically low (< 0.5-2%) in arid cropland areas of central and southern Spain while it may reach up to 21% in northern grasslands.
Main challenges for agricultural soils in Spain and related sustainable practices
The most concerning challenges of Spain’s Mediterranean areas are the extensive erosive processes and soil losses associated to semi-arid conditions, traditional agricultural practices, and arable land abandonment. In addition, inadequate long-term application of fertilizers has led to soil N losses, polluting surface, subterranean waters, and the atmosphere. Soil salinization is also of concern in some areas.
Several sustainable agricultural practices (SAPs) have been proposed to tackle those challenges as they would improve soil physical properties and biodiversity, potentially aiding in pest suppression and increasing crop yield. They encompass No- or Reduced-tillage (NT/RT), crop rotations, ground cover and cover crops, sowing legume-rich mixtures in dehesas, use of organic fertilizers, or increasing efficient fertilization and water management (Figures 1 and 2).
On top of the beneficial effects on agricultural soils, those practices may also mitigate potential environmental impacts, by increasing C sequestration, and reducing NO3 leaching or NH3 and greenhouse gas (GEI) emissions. They may also enhance soil water retention capacity and decrease erosion soil losses and water runoff. Their benefits are increased when applied in combination, but their actual implementation requires careful consideration of crop type and local conditions as their inappropriate use may induce undesirable side-effects.
Figure 2: Field experiment carried out at ”La Canaleja” experimental station (INIA) to assess the influence of different sustainable practices on nitrate leaching. Photo provided by Dr. José Luis Gabriel (INIA).
Barriers for the implementation of sustainable agricultural practices
Several barriers interfere with the wide implementation of SAPs in Spain, which might be overcome with proper educational and research approaches, and adequate policies and instruments.
One important barrier, originated in early educational stages, is the generalized public perception that soil is just a substrate supporting human activities, and not a connected environmental compartment crucial for our health and the provision of relevant ecosystem services. Other educational hurdles are the lack of training for cooperating in multidisciplinary teams (consumers, retailers, agri-food industry, farmers, researchers from different disciplines, policy makers, etc.) addressing soil-related issues, and connecting different spatial scales (plot, farm, landscape, and broader geographical units). These barriers should be solved by modernising current theoretical and practical courses of vocational education and university programmes.
The main research-related barriers are the fragmentation, reduced accessibility, and poor dissemination of existing knowledge, along with the small number of long-term studies aimed to properly shape and adapt SAPs to local conditions. In addition, there is scarcity of co-creation platforms involving academy, farmers and other relevant actors to test or improve science-driven schemes beyond the plot scale. Science-policies can help in overcoming those barriers by supporting data compilation, funding R&D and long-term experiments, fine-tuning existing programmes devoted to enhancing academia-farmer-industry interactions, and promoting knowledge dissemination to the general public.
Agricultural and environmental policies may also have a great impact in solving certain obstacles. There is no specific Spanish legislation for agricultural soils; only farm-related inputs and outputs of concern for particular environmental domains are regulated. Thus, national legislation promotes the appropriate use of plant protection agents and sewage sludges for agricultural use and defines the N-supply threshold from organic fertilizers that cannot be exceeded in nitrate-vulnerable zones. It also regulates agricultural impacts on surface and subterranean waters by establishing concentration limits for several agrochemicals, heavy metals and compounds associated to agronomic practices, including N-based substances.
A draft regulation for the sustainable nutrition of agricultural soils in Spain is now under revision. It compels to define a farm fertilization plan based on nutrient balances for the calculation of appropriate doses and applications, reducing thus adverse impacts on soil quality and biodiversity and the environment as a whole. Public authorities can also boost the effectiveness of SAPs at farm level by promoting their adaptation to local conditions and considering them in landscape territorial planning together with other measures such as afforestation or agroforestry practices, following agroecological principles.
The adoption of SAPs is also enhanced through provisions related with the EU Common Agricultural Policy (CAP). In addition, Spain is the leading country in Europe in terms of area devoted to organic farming, as supported by a specific sectorial strategy. Recent overarching policies enable the integration of specific regulations, such as the Integrated National Plan on Energy and Climate or the Long-term National Strategy (2050) for a modern, competitive and climatic neutral economy. These regulations take into account the potential of SAPs for both C sequestration and mitigation of GEI emissions and will be aligned with Spain’s future CAP strategic programme. Their objectives should be considered in the territorial planning associated to the upcoming Hydrological Plans (2021-2027) for the 25 Spanish river basin districts.
As Spain’s challenges are common to other European countries, the EJP Soil programme will be highly beneficial as it facilitates the provision of knowledge-driven solutions at the farm, landscape, and policy levels to address current agricultural soil challenges, subsequently benefiting farmers and society as a whole.
Authors: (1) Benjamin S. Gimeno, Technical Director of EJP-Soil Spain, INIA; (2) Diego S. Intrigliolo, Member of EJP-Soil Strategic Committee, CSIC; (3) María Luisa Tello, Technical support WP6 and WP7 of EJP-Soil, INIA; (4) Carlos García, Coordinator of SOILBIO research platform, CSIC.
For further information: Violeta Carrasco, e-mail: violeta.carrasco@inia.es