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Agricultural management plays an important role in global warming mitigation due to its effects on soil organic carbon (SOC) dynamics. In Mediterranean agroecosystems, the interactive effects of tillage and N fertilization on SOC storage have scarcely been studied. Hence, we here present a modelling study in which the effects of both tillage and N fertilization on SOC dynamics are investigated. We used SOC and C input data from a long-term (13 years) field study located in northeast Spain, firstly to validate both the Century model and the Rothamsted Carbon (RothC) model and secondly to predict future SOC dynamics until the year 2030. Tillage and N fertilization affected SOC stocks in the 0–30 cm soil layer. However, the interaction of the two factors was not significant. Averaged over the three N fertilization rates, the observed mean SOC stocks in conventional tillage (CT) and no-tillage (NT) were 29.8 and 36.8 Mg C ha−1, respectively. In addition, the observed SOC stocks, averaged for both tillage systems, increased with increasing N rates, with 30.6, 33.5 and 35.8 Mg C ha−1 for the 0, 60 and 120 kg N ha−1 rates, respectively. In general, both the Century model and the RothC model performed well in predicting SOC dynamics. Model predictions showed that in Mediterranean dryland agroecosystems SOC dynamics in the next 20 years would be variable according to the tillage and N fertilization applied. According to these predictions, scenarios with NT and high fertilization rates (e.g., 60–120 kg N ha−1) could lead to significant SOC sequestration and associated CO2 emission offsetting. However, these scenarios with high SOC sequestration rates also showed high mineral N accumulation in the soil profile with its associated environmental side effects. ; This work was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2010-22050-C03-01/02) and the European Union (FEDER funds). We acknowledge the Consejo Superior de Investigaciones Cientificas (CSIC) for the contract granted to Jorge Álvaro-Fuentes within the "Junta para la Ampliación de Estudios" (JAE-DOC) programme co-financed by the European Social Fund. Furthermore, Daniel Plaza-Bonilla was awarded a FPU fellowship by the Spanish Ministry of Education.

In Mediterranean agroecosystems, limited information exists about possible impacts of climate change on soil N2O emissions under different land uses. This paper presents a modelling study with a dual objective. Firstly, the biogeochemical Daycent model was evaluated to predict soil N2O emissions in different land uses in a typical Mediterranean agroecosystem. Secondly, the study aimed to determine the impact of climate change on soil N2O emissions in different Mediterranean land uses over an 85-year period. Soil N2O emissions were measured in three land uses (cropland, abandoned land and afforested land) over 18 months (December 2011 to June 2013) in a characteristic Mediterranean site in Spain. For climate change simulations, Daycent was run with and without atmospheric CO2 enrichment using climate data from the CGCM2-A2 model. The cumulative N2O emissions predicted by the Daycent model agreed well with the observed values. The lack of fit (LOFIT) and the relative error (E) statistics determined that the model error was not greater than the error in the measurements and that the bias in the simulation values was lower than the 95% confidence interval of the measurements. For the different land uses and climate scenarios, annual cumulative N2O emissions ranged from 126 to 642 g N2O-N ha−1 yr−1. Over the simulated 85-year period, climate change decreased soil N2O emissions in all three land uses. At the same time, under climate change, water filled pore space (WFPS) values decreased between 4% and 15% depending on the land use and climate change scenario considered. This study demonstrated the ability of the Daycent model to simulate soil N2O emissions in different land uses. According to model predictions, in Mediterranean conditions, climate change would lead to reduced N2O emissions in a range of land uses. ; Jorge Álvaro-Fuentes acknowledges the receipt of a fellowship from the OECD Co-operative Research Programme: Biological Resource Management in Sustainable Agricultural Systems in 2013. Daniel Plaza-Bonilla received a "Juan de la Cierva" grant from the Ministerio de Economía y Competitividad of Spain. This study was also possible through funds provided by the Aragon Regional Government and La Caixa (grant GA-LC-050/2011), the Ministry of Economy and Competitiveness of Spain (grant AGL2013-49062-C4-4-R) and the COMET-Global project (FACCE-JPI grant). We are grateful to María José Salvador and Javier Bareche for laboratory assistance.

30 Pags.- 1 Tabl. 5 Figs. The definitive version is available at: http://link.springer.com/journal/11104 ; Background and Aims The duration of soil organic carbon (SOC) sequestration in agricultural soils varies according to soil management, land-use history and soil and climate conditions. Despite several experiments have reported SOC sequestration with the adoption of no-tillage (NT) in Mediterranean dryland agroecosystems scarce information exists about the duration and magnitude of the sequestration process. For this reason, 20 years ago we established in northeast Spain a NT chronosequence experiment to evaluate SOC sequestration duration under Mediterranean dryland conditions. Methods In July 2010 we sampled five chronosequence phases with different years under NT (i.e., 1, 4, 11, and 20 years) and a continuous conventional tillage (CT) field, in which management prevailed unchanged during decades. Soil samples were taken at four depths: 0-5, 5-10, 10-20 and 20-30 cm. The SOC stocks were calculated from the SOC concentration and soil bulk density. Furthermore, we applied the Century ecosystem model to the different stages of the chronosequence to better understand the factors controlling SOC sequestration with NT adoption. Results Differences in SOC stocks were only found in the upper 5 cm soil layer in which 4, 11 and 20 years under NT showed greater SOC stocks compared with 1 year under NT and the CT phase. Despite no significant differences were found in the total SOC stock (0-30 cm soil layer) there was a noteworthy difference of 5.7 Mg ha-1 between the phase with the longest NT duration and the phase under conventional tillage. The maximum annual SOC sequestration occurred after 5 years of NT adoption with almost 50% change in the annual rate of SOC sequestration. NT sequestered SOC over the 20 years following the change in management. However, more than 75% of the total SOC sequestered was gained during the first 11 years after NT adoption. The Century model predicted reasonably well SOC stocks over the NT chronosequence. Conclusions In Mediterranean agroecosystems, despite the continuous use of NT has limited capacity for SOC sequestration, other environmental and agronomic benefits associated to this technique may justify the maintenance of NT over the long-term. ; This work was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2007-66320-CO2-02/AGR and AGL2010-22050-C03-01/02) and the European Union (FEDER funds). We acknowledge the Consejo Superior de Investigaciones Cientificas (CSIC) for the contract granted to Jorge Álvaro-Fuentes within the "Junta para la Ampliación de Estudios" (JAE-DOC) programme co-financed by the European Social Fund. Furthermore, Daniel Plaza-Bonilla was awarded with a FPU fellowship by the Spanish Ministry of Education. We thank Carlos Cortés and Silvia Martí for their technical assistance. ; Peer reviewed

Agricultural soils emit greenhouse gases (GHG). Excessive application of N fertilizer may lead to the accumulation of mineral N in the soil, which is susceptible to loss to the environment. The objective of this study was to quantify the effect of two levels of available mineral N before planting (L, low; H, high) and two rates of NH4NO3 fertilizer (0 and 300 kg N ha(-1)) on soil CH4, CO2, and N2O emissions in a sprinkler-irrigated corn (Zea mays L.) field located in northeastern Spain during two growing seasons (2011 and 2012). For both soil N levels at planting, several sampling dates showed higher N2O emissions in the 300 kg N ha(-1) treatment than the 0 kg N ha(-1) treatment. Applications of N fertilizer resulted in a short-lived increase of N2O emitted. Differences among fertilization treatments were found for soil CO2 emissions in 2011 and for soil N2O emissions in 2011 and 2012. No differences were found between treatments for CH4. In the 2012 season, the application of 300 kg N ha(-1) in the L scenario reduced N2O yield-scaled emissions (g N2O-N kg(-1) aboveground N uptake) by 30% due to a significant increase in corn yield (7.6 Mg grain ha(-1)) compared with the treatment without N. Conversely, under the H scenario, N application doubled yield-scaled N2O emissions. Results of this study demonstrate that fertilization strategies need to take into account mineral N levels in the soil before sowing to reduce GHG emissions during the growing season. ; We would like to thank Ana Bielsa, Mónica Guillén, María José Salvador, and Javier Bareche for laboratory and field assistance. This work was partially supported by the Aragon Government and La Caixa (Grant GA-LC-050/2011), the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2013-49062-C4-4-R, AGL2010- 22050-C03-01/02, and AGL2009-12897-C02-02), and the European Union (FEDER funds). Daniel Plaza-Bonilla received a "Juan de la Cierva" grant from the Ministerio de Economía y Competitividad of Spain. Finally, we are thankful to three anonymous reviewers for their valuable feedback and suggestions that led to further improvement of this manuscript.

36 Pags., 5 Tabls., 5 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987 ; Agricultural management plays an important role in global warming mitigation due to its effects on soil organic carbon (SOC) dynamics. In Mediterranean agroecosystems, the interactive effects of tillage and N fertilization on SOC storage have scarcely been studied. Hence, we here present a modelling study in which the effects of both tillage and N fertilization on SOC dynamics are investigated. We used SOC and C input data from a long-term (13 years) field study located in northeast Spain, firstly to validate both the Century model and the Rothamsted Carbon (RothC) model and secondly to predict future SOC dynamics until the year 2030. Tillage and N fertilization affected SOC stocks in the 0–30 cm soil layer. However, the interaction of the two factors was not significant. Averaged over the three N fertilization rates, the observed mean SOC stocks in conventional tillage (CT) and no-tillage (NT) were 29.8 and 36.8 Mg C ha−1, respectively. In addition, the observed SOC stocks, averaged for both tillage systems, increased with increasing N rates, with 30.6, 33.5 and 35.8 Mg C ha−1 for the 0, 60 and 120 kg N ha−1 rates, respectively. In general, both the Century model and the RothC model performed well in predicting SOC dynamics. Model predictions showed that in Mediterranean dryland agroecosystems SOC dynamics in the next 20 years would be variable according to the tillage and N fertilization applied. According to these predictions, scenarios with NT and high fertilization rates (e.g., 60–120 kg N ha−1) could lead to significant SOC sequestration and associated CO2 emission offsetting. However, these scenarios with high SOC sequestration rates also showed high mineral N accumulation in the soil profile with its associated environmental side effects. ; This work was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2010-22050-C03-01/02) and the European Union (FEDER funds). We acknowledge the Consejo Superior de Investigaciones Cientificas (CSIC) for the contract granted to Jorge Álvaro-Fuentes within the "Junta para la Ampliación de Estudios" (JAE-DOC) programme co-financed by the European Social Fund. Furthermore, Daniel Plaza-Bonilla was awarded a FPU fellowship by the Spanish Ministry of Education. ; Peer reviewed

Capítulo 1. Los fundamentos en la base conceptual -- Capítulo 2. Los fundamentos del proceso de planificación y el marco metodológico propuesto -- Capítulo 3. Los fundamentos en la formulación de la implantación -- Capítulo 4. Propuesta de acción para la concertación del plan: un ejemplo

An integrated assessment of the potential of different management practices for mitigating specific components of the total GHG budget (N2O and CH4 emissions and C sequestration) of Mediterranean agrosystems was performed in this study. Their suitability regarding both yield and environmental (e.g. nitrate leaching and ammonia volatilization) sustainability, and regional barriers and opportunities for their implementation were also considered. Based on its results best strategies to abate GHG emissions in Mediterranean agro-systems were proposed. Adjusting N fertilization to crop needs in both irrigated and rain-fed systems could reduce N2O emissions up to 50% compared with a non-adjusted practice. Substitution of N synthetic fertilizers by solid manure can be also implemented in those systems, and may abate N2O emissions by about 20% under Mediterranean conditions, with additional indirect benefits associated to energy savings and positive effects in crop yields. The use of urease and nitrification inhibitors enhances N use efficiency of the cropping systems and may mitigate N2O emissions up to 80% and 50%, respectively. The type of irrigation may also have a great mitigation potential in the Mediterranean region. Drip-irrigated systems have on average 80% lower N2O emissions than sprinkler systems and drip-irrigation combined with optimized fertilization showed a reduction in direct N2O emissions up to 50%. Methane fluxes have a relatively small contribution to the total GHG budget of Mediterranean crops, which can mostly be controlled by careful management of the water table and organic inputs in paddies. Reduced soil tillage, improved management of crop residues and agro-industry by-products, and cover cropping in orchards, are the most suitable interventions to enhance organic C stocks in Mediterranean agricultural soils. The adoption of the proposed agricultural practices will require farmers training. The global analysis of life cycle emissions associated to irrigation type (drip, sprinkle and furrow) and N fertilization rate (100 and 300 kg N ha 1 yr 1) revealed that these factors may outweigh the reduction in GHG emissions beyond the plot scale. The analysis of the impact of some structural changes on top-down mitigation of GHG emissions revealed that 3-15% of N2O emissions could be suppressed by avoiding food waste at the end-consumer level. A 40% reduction in meat and dairy consumption could reduce GHG emissions by 20-30%. Reintroducing the Mediterranean diet (i.e. 35% intake of animal protein) would therefore result in a significant decrease of GHG emissions from agricultural production systems under Mediterranean conditions. ; The authors would like to thank the Spanish National R+D+i Plan (AGL2012-37815-C05-01, AGL2012-37815-C05-04) and very specifically the workshop held in December 2016 in Butrón (Bizkaia) to synthesize the most promising measures to reduce N2O emissions from Spanish agricultural soils. BC3 is sponsored by the Basque Government. M. L. Cayuela thanks Fundación Seneca for financing the project 19281/PI/14. This paper has been produced within the context of the REMEDIA network.

88 Pags.- 4 Figs.- 3 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809 This article belongs to a special issue "Quantification and mitigation of greenhouse gas emissions in Mediterranean cropping systems" / Edited By Alberto Sanz-Cobena, Luis Lassaletta, Josette Garnier and Pete Smith, available at http://www.sciencedirect.com/science/journal/01678809/238/supp/C ; An integrated assessment of the potential of different management practices for mitigating specific components of the total GHG budget (N2O and CH4 emissions and C sequestration) of Mediterranean agrosystems was performed in this study. Their suitability regarding both yield and environmental (e.g. nitrate leaching and ammonia volatilization) sustainability, and regional barriers and opportunities for their implementation were also considered. Based on its results best strategies to abate GHG emissions in Mediterranean agro-systems were proposed. Adjusting N fertilization to crop needs in both irrigated and rain-fed systems could reduce N2O emissions up to 50% compared with a non-adjusted practice. Substitution of N synthetic fertilizers by solid manure can be also implemented in those systems, and may abate N2O emissions by about 20% under Mediterranean conditions, with additional indirect benefits associated to energy savings and positive effects in crop yields. The use of urease and nitrification inhibitors enhances N use efficiency of the cropping systems and may mitigate N2O emissions up to 80% and 50%, respectively. The type of irrigation may also have a great mitigation potential in the Mediterranean region. Drip-irrigated systems have on average 80% lower N2O emissions than sprinkler systems and drip-irrigation combined with optimized fertilization showed a reduction in direct N2O emissions up to 50%. Methane fluxes have a relatively small contribution to the total GHG budget of Mediterranean crops, which can mostly be controlled by careful management of the water table and organic inputs in paddies. Reduced soil tillage, improved management of crop residues and agro-industry by-products, and cover cropping in orchards, are the most suitable interventions to enhance organic C stocks in Mediterranean agricultural soils. The adoption of the proposed agricultural practices will require farmers training. The global analysis of life cycle emissions associated to irrigation type (drip, sprinkle and furrow) and N fertilization rate (100 and 300 kg N ha−1 yr−1) revealed that these factors may outweigh the reduction in GHG emissions beyond the plot scale. The analysis of the impact of some structural changes on top-down mitigation of GHG emissions revealed that 3–15% of N2O emissions could be suppressed by avoiding food waste at the end-consumer level. A 40% reduction in meat and dairy consumption could reduce GHG emissions by 20–30%. Reintroducing the Mediterranean diet (i.e. ∼35% intake of animal protein) would therefore result in a significant decrease of GHG emissions from agricultural production systems under Mediterranean conditions. ; The authors would like to thank the Spanish National R+D+i Plan (AGL2012-37815-C05-01, AGL2012-37815-C05-04) and very specifically the workshop held in December 2016 in Butrón (Bizkaia) to synthesize the most promising measures to reduce N2O emissions from Spanish agricultural soils. BC3 is sponsored by the Basque Government. M. L. Cayuela thanks Fundación Seneca for financing the project 19281/PI/14. This paper has been produced within the context of the REMEDIA network: http://redremedia.wordpress.com/. ; Peer reviewed