• Energy Research

Abstract Synthetic nitrogen (N) fertilization has helped boost agricultural yields, but it is also responsible for direct and indirect greenhouse gas (GHG) emissions. Fertilizer-related emissions are also promoted by irrigation and manure application, which has increased with livestock industrialization. Spanish agriculture provides a paradigmatic example of high industrialization under two different climates (temperate and Mediterranean) and two contrasting water management regimes (rainfed and irrigated). In this study, we estimated the historical evolution of the C footprint of N fertilization (including all the life cycle GHG emissions related to N fertilization) in Spanish agriculture from 1860 to 2018 at the province level (50 provinces) for 122 crops, using climate-specific N2O emission factors (EFs) adjusted to the type of water management and the N source (synthetic fertilizer, animal manure, crop residues and soil N mineralization) and considering changes in the industrial efficiency of N fertilizer production. Overall, N-related GHG emissions increased ∼12-fold, up to 10–14 Tg CO2e yr−1 in the 2010s, with much higher growth in Mediterranean than in temperate areas. Direct N2O EFs of N fertilizers doubled due to the expansion of irrigation, synthetic fertilizers and liquid manure, associated with livestock industrialization. Synthetic N production dominated the emissions balance (55%–60% of GHGe in the 21st century). Large energy efficiency gains of industrial fertilizer production were largely offset by the changes in the fertilizer mix. Downstream N2O emissions associated with NH3 volatilization and NO3 − leaching increased tenfold. The yield-scaled carbon footprint of N use in Spanish agriculture increased fourfold, from 4 and 5 Mg CO2e Mg N−1 to 16–18 Mg CO2e Mg N−1. Therefore, the results reported herein indicate that increased productivity could not offset the growth in manufacture and soil emissions related to N use, suggesting that mitigation efforts should not only aim to increase N use efficiency but also consider water management, fertilizer type and fertilizer manufacture as key drivers of emissions.

Mediterranean olive growing characterizes, identifies, and can sustain the socioeconomic viability of rural areas, not only through the production of primary products but also through the management of renewable natural resources, and the conservation of landscape and biodiversity. However, high levels of mechanization, monocultures, intensive farming techniques, and the use of synthetic pesticides and fertilizers are threatening the environment and affecting rural communities in turn. In the last years, the agroecological discourse emerged as a transdisciplinary science merging agronomy, ecology, and socioeconomic sciences with the purpose of responding to socioeconomic and environmental concerns, responding to the globalized industrial food processing and intensive agriculture. In this context, the research project Sustainolive, guided by an international consortium of stakeholders from academia and the productive sector, has the aim of promoting sustainability in the olive oil sector through the implementation and promotion of innovative and technological solutions based on agroecological concepts. Through an innovative, transdisciplinary, and multi-actor approach, Sustainolive combines different types of knowledge (e.g., scientific, empirical, and traditional), disciplines (ranging from engineering to the humanities), and methodological approaches (e.g., Life Cycle Sustainability Assessment, Social Agrarian Metabolism and multicriterial analysis tools) to provide practical solutions that address the complexity of the olive sector. The results from the application of this methodology are expected to highlight which agroecological practices are more environmentally, economically, and socially sustainable and uncover how Mediterranean societies use agrarian biophysical resources.

Soil organic carbon (SOC) management is key for soil fertility and for mitigation and adaptation to climate change, particularly in desertification-prone areas such as Mediterranean croplands. Industrialization and global change processes affect SOC dynamics in multiple, often opposing, ways. Here we present a detailed SOC balance in Spanish cropland from 1900 to 2008, as a model of a Mediterranean, industrialized agriculture. Net Primary Productivity (NPP) and soil C inputs were estimated based on yield and management data. Changes in SOC stocks were modeled using HSOC, a simple model with one inert and two active C pools, which combines RothC model parameters with humification coefficients. Crop yields increased by 227% during the studied period, but total C exported from the agroecosystem only increased by 73%, total NPP by 30%, and soil C inputs by 20%. There was a continued decline in SOC during the 20th century, and cropland SOC levels in 2008 were 17% below their 1933 peak. SOC trends were driven by historical changes in land uses, management practices and climate. Cropland expansion was the main driver of SOC loss until mid-20th century, followed by the decline in soil C inputs during the fast agricultural industrialization starting in the 1950s, which reduced harvest indices and weed biomass production, particularly in woody cropping systems. C inputs started recovering in the 1980s, mainly through increasing crop residue return. The upward trend in SOC mineralization rates was an increasingly important driver of SOC losses, triggered by irrigation expansion, soil cover loss and climate change-driven temperature rise.

Current European agriculture policies and strategies are aimed to boost the transition from the predominant conventional to a more environmentally friendly agriculture model. As part of this, it is crucial to identify the barriers that exist to implementing crop-specific management practices so that appropriate mitigating steps to overcome these can be executed. Participatory action research, where farmers are research actors rather than objects, is essential to identify the main barriers farmers have to face. The objective of this study was to identify the main barriers to the adoption of a combination of sustainable management practices in olive cropping in Southern Spain. A 20-item questionnaire was designed and responded to by 200 Spanish olive farmers. Exploratory and confirmatory factor analyses were used to assess the factor structure. The final best fit model included 14 items that were grouped in the following four barriers or facilitators: “lack of training/formation”, and “lack of economic/policy support” as barriers; “wellbeing–nature connection” and “environmental impact awareness” as facilitators. The mean scores on the different factors were higher than the theoretical mean, so the identification of the two barriers and the two facilitators for implementing sustainable practices was robust. Farmers, especially women, are concerned about their knowledge limitation in implementing sustainable management practices, which opens a window of opportunity for specific actions (i.e., training and demonstrative events) to be taken for accomplishing the agriculture sector transformation.