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39 Pags., 5 Tabls., 4 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809 ; The interactive effects of climatechange and atmospheric CO2 rise could have potential effects on both soilorganiccarbon (SOC) storage and the capability of certain management practices to sequester atmospheric carbon (C) in soils. In this study, we present the first regional estimation of SOC stock changes under climatechange in Spanish agroecosystems. The Century model was applied over a 80-yr period (i.e., from 2007 to 2087) to an agricultural area of 40,498 km2 located in northeast Spain under five different climate scenarios. The model predicted an increase in SOC storage in the 0–30 cm soil depth in all the climatechange scenarios tested (i.e., ECHAM4-A2, ECHAM4-B2, CGCM2-A2 and CGCM2-B2). Among climatechange scenarios, SOC stock changes ranged from 0.15 to 0.32 Tg C yr−1. The Century model also predicted differences in SOC sequestration among agricultural classes. At the end of the simulation period, the greatest SOC stocks were found in the rainfed arable land under monoculture and no-tillage (MC-NT) class and in the grape-olive (GO) class with average stocks greater than 80 Mg C ha−1. On the contrary, both the alfalfa (AF) and the cereal-fallow (CF) classes showed the lowest SOC stocks with predicted values lower than 60 Mg C ha−1. Under climatechange conditions, Spanish agriculturalsoils could act as potential atmospheric C sinks. Nevertheless, both the magnitude of the change in climate and the adoption of beneficial management practices could be critical in maximizing SOC sequestration. ; Jorge Álvaro-Fuentes was awarded with a Beatriu de Pinós Postdoctoral Fellowship by the Comissionat per a Universitats i Recerca del Departament d'Innovació, Universitats i Empresa, of the Generalitat de Catalunya and recently with a contract of the "Junta para la Ampliación de Estudios" (JAE-DOC) programme of the Consejo Superior de Investigaciones Cientificas (CSIC) co-financed by the European Social Fund. This work was partly supported by the Aragon Government and La Caixa (grant GA-LC-050/2011), the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL2010-22050-C03-01/02) and the European Union (FEDER funds). ; Peer reviewed

In the European Union, various crop diversification systems such as crop rotation, intercropping and multiple cropping, as well as low-input management practices, have been promoted to sustain crop productivity while maintaining environmental quality and ecosystem services. We conducted a data analysis to identify the benefits of crop associations, alternative agricultural practices and strategies in four selected regions of Europe (Atlantic, Boreal, Mediterranean North and Mediterranean South) in terms of crop production (CP). The dataset was derived from 54 references with a total of 750 comparisons and included site characteristics, crop information (diversification system, crop production, tillage and fertilization management) and soil parameters. We analyzed each effect separately, comparing CP under tillage management (e.g., conventional tillage vs. no tillage), crop diversification (e.g., monoculture vs. rotation), and fertilization management (e.g., mineral fertilization vs. organic fertilization). Compared with conventional tillage (CT), CP was higher by 12% in no tillage (NT), in fine- and medium-textured soils (8&ndash ; 9%) and in arid and semiarid sites located in the Mediterranean Region (24%). Compared to monoculture, diversified cropping systems with longer crop rotations increased CP by 12%, and by 12% in soils with coarse and medium textures. In relation to fertilization, CP was increased with the use of slurry (40%), and when crop residues were incorporated (39%) or mulched (74%). Results showed that conversion to alternative diversified systems through the use of crop rotations, with NT and organic fertilization, results in a better crop performance. However, regional differences related to climate and soil-texture-specific responses should be considered to target local measures to improve soil management.

Agricultural management practices play an important role in greenhouse gases (GHG) emissions due to their impact on the soil microenvironment. In this study, two experiments were performed to investigate the influence of tillage and N fertilization on GHG production at the macroaggregate scale. In the first experiment, soil macroaggregates collected from a field experiment comparing various soil management systems (CT, conventional tillage; NT, no-tillage) and N fertilization types (a control treatment without N and mineral N and organic N with pig slurry treatments both at 150kgNha-1) were incubated for 35 days. Methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) production was quantified at regular time intervals by gas chromatography. In the second experiment, the effects of fertilization type and soil moisture on the relative importance of nitrification and denitrification processes in N2O emission from soil macroaggregates were quantified. Nitrate ammonium, macroaggregate-C concentration, macroaggregate water-stability, microbial biomass-C and N (MBC and MBN, respectively) and water-soluble C (WSC) were determined. While NT macroaggregates showed methanotrophic activity, CT macroaggregates acted as net CH4 producers. However, no significant differences were found between tillage systems on the fluxes and cumulative emissions of CO2 and N2O. Greatest cumulative CO2 emissions, macroaggregate-C concentration and WSC were found in the organic N fertilization treatment and the lowest in the control treatment. Moreover, a tillage and N fertilization interactive effect was found in macroaggregate CO2 production: while the different types of N fertilizers had no effects on the emission of CO2 in the NT macroaggregates, a greater CO2 production in the CT macroaggregates was observed for the organic fertilization treatment compared with the mineral and control treatments. The highest N2O losses due to nitrification were found in the mineral N treatment while denitrification was the main factor affecting N2O losses in the organic N treatment. Our results suggest that agricultural management practices such as tillage and N fertilization regulate GHG production in macroaggregates through changes in the proportion of C and N substrates and in microbial activity. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01/02) and by the Aragon Government and La Caixa (grant GA-LC-050/2011).

49 Pags., 6 Tabls., 4 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/00380717 ; Agricultural management practices play an important role in greenhouse gases (GHG) emissions due to their impact on the soil microenvironment. In this study, two experiments were performed to investigate the influence of tillage and N fertilization on GHG production at the macroaggregate scale. In the first experiment, soil macroaggregates collected from a field experiment comparing various soil management systems (CT, conventional tillage; NT, no-tillage) and N fertilization types (a control treatment without N and mineral N and organic N with pig slurry treatments both at 150kgNha-1) were incubated for 35 days. Methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) production was quantified at regular time intervals by gas chromatography. In the second experiment, the effects of fertilization type and soil moisture on the relative importance of nitrification and denitrification processes in N2O emission from soil macroaggregates were quantified. Nitrate ammonium, macroaggregate-C concentration, macroaggregate water-stability, microbial biomass-C and N (MBC and MBN, respectively) and water-soluble C (WSC) were determined. While NT macroaggregates showed methanotrophic activity, CT macroaggregates acted as net CH4 producers. However, no significant differences were found between tillage systems on the fluxes and cumulative emissions of CO2 and N2O. Greatest cumulative CO2 emissions, macroaggregate-C concentration and WSC were found in the organic N fertilization treatment and the lowest in the control treatment. Moreover, a tillage and N fertilization interactive effect was found in macroaggregate CO2 production: while the different types of N fertilizers had no effects on the emission of CO2 in the NT macroaggregates, a greater CO2 production in the CT macroaggregates was observed for the organic fertilization treatment compared with the mineral and control treatments. The highest N2O losses due to nitrification were found in the mineral N treatment while denitrification was the main factor affecting N2O losses in the organic N treatment. Our results suggest that agricultural management practices such as tillage and N fertilization regulate GHG production in macroaggregates through changes in the proportion of C and N substrates and in microbial activity. ; D. Plaza-Bonilla was awarded an FPU fellowship by the Spanish Ministry of Education. This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01/02) and by the Aragon Government and La Caixa (grant GA-LC-050/2011). ; Peer Reviewed

Pags.- 8 Tabls.- 6 Figs. The definitive version is available at: http://link.springer.com/journal/11027 ; Small changes in agricultural practices have a large potential for reducing greenhouse gas emissions. However, the implementation of such practices at the local level is often limited by a range of barriers. Understanding the barriers is essential for defining effective measures, the actual mitigation potential of the measures, and the policy needs to ensure implementation. Here we evaluate behavioural, cultural, and policy barriers for implementation of mitigation practices at the local level that imply small changes to farmers. The choice of potential mitigation practices relevant to the case study is based on a literature review of previous empirical studies. Two methods that include the stakeholders' involvement (experts and farmers) are undertaken for the prioritization of these potential practices: (a) Multi-criteria analysis (MCA) of the choices of an expert panel and (b) Analysis of barriers to implementation based on a survey of farmers. The MCA considers two future climate scenarios – current climate and a drier and warmer climate scenario. Results suggest that all potential selected practices are suitable for mitigation considering multiple criteria in both scenarios. Nevertheless, if all the barriers for implementation had the same influence, the preferred mitigation practices in the case study would be changes in fertilization management and use of cover crops. The identification of barriers for the implementation of the practices is based on the econometric analysis of surveys given to farmers. Results show that farmers' environmental concerns, financial incentives and access to technical advice are the main factors that define their barriers to implementation. These results may contribute to develop effective mitigation policy to be included in the 2020 review of the European Union Common Agricultural Policy. ; Peer reviewed

Small changes in agricultural practices have a large potential for reducing greenhouse gas emissions. However, the implementation of such practices at the local level is often limited by a range of barriers. Understanding the barriers is essential for defining effective measures, the actual mitigation potential of the measures, and the policy needs to ensure implementation. Here we evaluate behavioural, cultural, and policy barriers for implementation of mitigation practices at the local level that imply small changes to farmers. The choice of potential mitigation practices relevant to the case study is based on a literature review of previous empirical studies. Two methods that include the stakeholders? involvement (experts and farmers) are undertaken for the prioritization of these potential practices: (a) Multi-criteria analysis (MCA) of the choices of an expert panel and (b) Analysis of barriers to implementation based on a survey of farmers. The MCA considers two future climate scenarios ? current climate and a drier and warmer climate scenario. Results suggest that all potential selected practices are suitable for mitigation considering multiple criteria in both scenarios. Nevertheless, if all the barriers for implementation had the same influence, the preferred mitigation practices in the case study would be changes in fertilization management and use of cover crops. The identification of barriers for the implementation of the practices is based on the econometric analysis of surveys given to farmers. Results show that farmers? environmental concerns, financial incentives and access to technical advice are the main factors that define their barriers to implementation. These results may contribute to develop effective mitigation policy to be included in the 2020 review of the European Union Common Agricultural Policy.

[SPA] Este libro recopila diferentes protocolos para el análisis de plantas y suelos para sistemas agrícolas. Nuestro objetivo es proporcionar un conjunto completo de indicadores para evaluar la productividad de los cultivos, la calidad de los cultivos, la calidad del suelo y la fertilidad del suelo con procedimientos y métodos viables y sólidos. La evaluación de la sostenibilidad de los agroecosistemas requiere la selección de indicadores adecuados y su medida. El presente manual ha compilado diferentes indicadores para evaluar el crecimiento de los cultivos, la incidencia de plagas y enfermedades, el rendimiento de la granja, la calidad de los cultivos y las características nutricionales, los análisis físicos del suelo, los análisis químicos del suelo y los análisis biológicos del suelo. El libro está organizado en tres partes: i) análisis de plantas y cultivos, ii) análisis físico-químicos del suelo y iii) análisis biológicos del suelo. En total, proporcionamos 90 procedimientos para el análisis de plantas y suelos, incluida la importancia y las aplicaciones, el principio del método descrito, los reactivos necesarios, los materiales y equipos, la descripción detallada del procedimiento, los cálculos necesarios y algunas observaciones específicas. ; [ENG] This books compiles different protocols for analysis of plant and soil for agricultural systems. We aim to provide a complete set of indicators to assess crop productivity, crop quality, soil quality and soil fertility with feasible and robust procedures and methods. The assessment of the sustainability of agroecosystems needs the selection of suitable indicators and their measure. The present handbook has compiled different indicators to assess crop growth, incidence of pests and diseases, farm yield, crop quality and nutritional characteristics, soil physical analyses, soil chemical analyses and soil biological analyses. The book is organized in three parts: i) plant and crop analyses, ii) soil physicochemical analyses and iii) soil biological analyses. In total we provide 90 procedures for plant and soil analysis, including the importance and applications, the principle of the method described, the reagents needed, the materials and equipment, the detailed description of the procedure, the calculations required and some specific remarks. ; This project has received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No 728003

23 Pags.- 8 Tabls.- 2 Figs. © 2021 Jebari et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ; Temperate grassland soils store significant amounts of carbon (C). Estimating how much livestock grazing and manuring can influence grassland soil organic carbon (SOC) is key to improve greenhouse gas grassland budgets. The Rothamsted Carbon (RothC) model, although originally developed and parameterized to model the turnover of organic C in arable topsoil, has been widely used, with varied success, to estimate SOC changes in grassland under different climates, soils, and management conditions. In this paper, we hypothesise that RothC-based SOC predictions in managed grasslands under temperate moist climatic conditions can be improved by incorporating small modifications to the model based on existing field data from diverse experimental locations in Europe. For this, we described and evaluated changes at the level of: (1) the soil water function of RothC, (2) entry pools accounting for the degradability of the exogenous organic matter (EOM) applied (e.g., ruminant excreta), (3) the month-on-month change in the quality of C inputs coming from plant residues (i.e above-, below-ground plant residue and rhizodeposits), and (4) the livestock trampling effect (i.e., poaching damage) as a common problem in areas with higher annual precipitation. In order to evaluate the potential utility of these changes, we performed a simple sensitivity analysis and tested the model predictions against averaged data from four grassland experiments in Europe. Our evaluation showed that the default model's performance was 78% and whereas some of the modifications seemed to improve RothC SOC predictions (model performance of 95% and 86% for soil water function and plant residues, respectively), others did not lead to any/or almost any improvement (model performance of 80 and 46% for the change in the C input quality and livestock trampling, respectively). We concluded that, whereas adding more complexity to the RothC model by adding the livestock trampling would actually not improve the model, adding the modified soil water function and plant residue components, and at a lesser extent residues quality, could improve predictability of the RothC in managed grasslands under temperate moist climatic conditions. ; We gratefully acknowledge the financial support of the Fundación Cándido de Iturriaga y Maria del Dañobeitia, Juan de la Cierva and the European Union's Horizon 2020 Research and Innovation Action (RIA) through the project "Innovation for sustainable sheep and Goat production in Europe (iSAGE)" undergrant agreement No 679302. BC3 is supported by the Basque Government through the BERC 2018-2021 program and by Spanish Ministry of Economy and Competitiveness MINECO through BC3 María de Maeztu excellence accreditation MDM-2017-0714. Agustin del Prado is financed by the programme Ramon y Cajal from the Spanish Ministry of Economy, Industry and Competitiveness (RYC2017-22143). María Almagro was supported by the Juan de la Cierva Program (grant IJCI-2015- 23500). F ; Peer reviewed

There is a strong need to identify the combination of tillage and N fertilization practices that reduce the amount of nitrous oxide (N2O) emissions while maintaining crop productivity in dryland Mediterranean areas. We measured the fluxes of N2O in two field experiments with 3 and 15 years since their establishment. In the long-term experiment, two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three mineral N fertilization rates (0, 60 and 120 kg N ha−1) were compared. In the short-term experiment, the same tillage systems (CT and NT) and three N fertilization doses (0, 75 and 150 kg N ha−1) and two types of fertilizers (mineral N and organic N with pig slurry) were compared. N2O emissions, water-filled pore space, soil mineral N content, grain yields, N-biomass inputs and soil total nitrogen (STN) stocks were quantified and the N2O yield-scaled ratio as kg of CO2 equivalents per kg of grain produced was calculated. In both experiments tillage treatments significantly affected the dynamics of N2O fluxes. Cumulative losses of N as N2O were similar between tillage treatments in the long-term field experiment. Contrarily, although not significant, cumulative N losses were about 35% greater under NT than CT in the short-term experiment. NT significantly increased the production of grain and the inputs of N to the soil as above-ground biomass in both experiments. Averaged across fertilizer treatments, CT emitted 0.362 and 0.104 kg CO2 equiv. kg grain−1 in the long-term and the short-term experiment, respectively, significantly more than NT that emitted 0.033 and 0.056 kg CO2 equiv. kg grain−1, respectively. Nitrogen fertilization rates did not affect the average N2O fluxes or the total N losses during the period of gas measurement in the long-term experiment. Contrarily, in the short-term experiment, N2O emissions increased with application rate for both mineral and organic fertilizers. The use of pig slurry increased grain production when compared with the mineral N treatment, thus reducing the yield-scaled emissions of N2O by 44%. Our results showed that in rainfed Mediterranean agroecosystems, the use of NT and pig slurry are effective means of yield-scaled N2O emissions reduction. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01/02), the Aragon Government and La Caixa (grant GA-LC-050/2011), the Department of Agriculture of the Catalonia Government (grant 2012 AGEC 00012) and the European Union (FEDER funds).

This study focuses on the quantification of soil water storage and crop yield under different tillage systems in dryland semiarid Mediterranean conditions. Three long-term tillage experiments based on cereal production were initiated in 1987, 1990 and 1992, at three different locations in the Ebro river valley (NE Spain): El Canós, Selvanera and Agramunt, with an increasing degree of aridity. Different tillage intensities were compared in each experiment using different implements: no tillage (NT), minimum tillage (MT), chisel (Ch), subsoiler up to 25 cm depth (Sub-25) and up to 50 cm (Sub-50), and mouldboard plough (Mb). Soil water content (SWC) up to 100 cm, soil water storage (SWS), precipitation storage efficiency (PSE) and crop yield were quantified during 8 (El Canós) and 19 years (Selvanera and Agramunt). The use of MT (at Selvanera) and NT (at El Canós and Agramunt) led to the highest SWC after the storage period (i.e. from previous harvest to crop tillering), with a major role played by the storage of water at deep soil layers. At Agramunt, Mb presented the lowest SWS when compared to Ch, Sub-50 and NT, and, consequently, the lowest post-tillering evapotranspiration. On the contrary, no differences were found between tillage systems on SWS at El Canós or at Selvanera. Significant yield differences were found at Agramunt being: NT > Sub-50 > Ch = Mb. These differences were especially important in years with mean yield below 2000 kg ha-1, in which NT obtained the highest productions. At Selvanera yield was greater under conservation tillage (NT, MT) than under intensive tillage (Sub-50). Contrarily, no yield differences were found between tillage systems at El Canós, the site with the lowest water deficit, where crop residues were removed. A strong linear relationship was found between SWS and yield at Agramunt and Selvanera. At Agramunt the relationship presented a greater slope under Mb. In this site, in years with previous harvest-to-tillering SWS below 100 mm and with precipitation over 100 mm between tillering and anthesis, yields were, as an average, 1245 kg ha-1 higher than in standard years. This study demonstrates that under semiarid rainfed conditions, soil water storage increases with the use of conservation tillage systems, being amplified with the degree of aridity of the site. The relationship between water stored in the soil and crop yield and its reliability is site-specific. Once determined, it could be used to predict yield at the end of the vegetative phase of the crop to help take management decisions. ; This work was funded by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of the Spanish Government, AGR91-312, AGF94-198, AGF98-261-C02,AGL2001- 2238-CO2-02, AGL2004-7763-C02-01, AGL2007- 66320-C02-01, AGL-2010-22050-C03-01, AGL2013-49062-C4-1projects. We also thank the farmers that collaborate in the development of the project, Josep Maria Besora, Josep Gabernet and Jaume Ramón. We especiallyacknowledge Jaume Gregori for hisinvolvement and technical support during the development of the experiments.

36 Pags.- 6 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03784290 ; This study focuses on the quantification of soil water storage and crop yield under different tillage systems in dryland semiarid Mediterranean conditions. Three long-term tillage experiments based on cereal production were initiated in 1987, 1990 and 1992, at three different locations in the Ebro river valley (NE Spain): El Canós, Selvanera and Agramunt, with an increasing degree of aridity. Different tillage intensities were compared in each experiment using different implements: no tillage (NT), minimum tillage (MT), chisel (Ch), subsoiler up to 25 cm depth (Sub-25) and up to 50 cm (Sub-50), and mouldboard plough (Mb). Soil water content (SWC) up to 100 cm, soil water storage (SWS), precipitation storage efficiency (PSE) and crop yield were quantified during 8 (El Canós) and 19 years (Selvanera and Agramunt). The use of MT (at Selvanera) and NT (at El Canós and Agramunt) led to the highest SWC after the storage period (i.e., from previous harvest to crop tillering), with a major role played by the storage of water at deep soil layers. At Agramunt, Mb presented the lowest SWS when compared to Ch, Sub-50 and NT, and, consequently, the lowest post-tillering evapotranspiration. On the contrary, no differences were found between tillage systems on SWS at El Canós or at Selvanera. Significant yield differences were found at Agramunt being: NT > Sub-50 > Ch = Mb. These differences were especially important in years with mean yield below 2000 kg ha−1, in which NT obtained the highest productions. At Selvanera yield was greater under conservation tillage (NT, MT) than under intensive tillage (Sub-50). Contrarily, no yield differences were found between tillage systems at El Canós, the site with the lowest water deficit, where crop residues were removed. A strong linear relationship was found between SWS and yield at Agramunt and Selvanera. At Agramunt the relationship presented a greater slope under Mb. In this site, in years with previous harvest-to-tillering SWS below 100 mm and with precipitation over 100 mm between tillering and anthesis, yields were, as an average, 1245 kg ha−1 higher than in standard years. This study demonstrates that under semiarid rainfed conditions, soil water storage increases with the use of conservation tillage systems, being amplified with the degree of aridity of the site. The relationship between water stored in the soil and crop yield and its reliability is site-specific. Once determined, it could be used to predict yield at the end of the vegetative phase of the crop to help take management decisions. ; This work was funded by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of the Spanish Government, AGR91-312, AGF94-198, AGF98-261-C02, AGL2001-2238-CO2-02, AGL2004-7763-C02-01, AGL2007-66320-C02-01, AGL-2010-22050-C03-01, AGL2013-49062-C4-1 projects. ; Peer reviewed

In semiarid Mediterranean agroecosystems, low and erratic annual rainfall together with the widespread use of mouldboard ploughing (conventional tillage, CT), as the main traditional tillage practice, has led to a depletion of soil organic matter (SOM) and with increases in CO2 emissions from soil to the atmosphere. In this study, we evaluated the viability of conservation tillage: RT, reduced tillage (chisel and cultivator ploughing) and, especially, NT (no-tillage) to reduce short-term (from 0 to 48 h after a tillage operation) and mid-term (from 0 h to several days since tillage operation) tillage-induced CO2 emissions. The study was conducted in three long-term tillage experiments located at different sites of the Ebro river valley (NE Spain) across a precipitation gradient. Soils were classified as: Fluventic Xerocrept, Typic Xerofluvent and Xerollic Calciorthid. Soil temperature and water content were also measured in order to determine their influence on tillage-induced CO2 fluxes. The majority of the CO2 flux measured immediately after tillage ranged from 0.17 to 6 g CO2 m−2 h−1 and was from 3 to 15 times greater than the flux before tillage operations, except in NT where soil CO2 flux was low and steady during the whole study period. Mid-term CO2 emission showed a different trend depending on the time of the year in which tillage was implemented. Microclimatic soil conditions (soil temperature and water content) had little impact on soil CO2 emission following tillage. In the semiarid Mediterranean agroecosystems studied, NT had low short-term soil CO2 efflux compared with other soil tillage systems (e.g., conventional and reduced tillage) and therefore can be recommended to better manage C in soil. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL 2001-2238-C02-01 and AGL 2004-07763-C02-02) and the European Union (FEDER funds). The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education.

Long-term tillage negatively affects soil aggregation, but little is known about the short-term effects of tillage. We investigated the effects of intensive tillage (moldboard plowing) and conservation tillage (chisel plowing) on aggregate breakage during tillage in a long-term study located in the semiarid Ebro river valley (NE Spain). The type of tillage resulted in different soil aggregate distributions. In the 0–5-cm and 5–10-cm soil layers, chisel plowing decreased dry mean weight diameter (DMWD) 29% and 35%, respectively, while moldboard plowing decreased DMWD by only 2% and 16%, respectively. The decrease in DMWD was mainly due to breaking of large aggregates ranging (2–8 mm) into small aggregates (<0.5 mm). Tillage method had no effect on water stability of 1–2 mm aggregates. The differences in DMWD demonstrate that the choice of the tillage implement can be a key factor in improving soil management and productivity. The surprising result that aggregate breakdown was greater with chisel than moldboard plowing needs further research to determine the mechanisms controlling aggregate breaking during tillage. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01, AGL 2004-07763-C02-02, AGL2007-66320-CO2-02/AGR) and the European Union (FEDER funds).

Losses of soil organic carbon (SOC) have contributed to CO2 emissions from soils to the atmosphere and to global climate change. We hypothesized that in semiarid agroecosystems of the Mediterranean region, a shift from the traditional management system (including conventional tillage [CT] and a cereal–fallow rotation) to a more conservative system, including no-till (NT) and continuous cropping, could reduce CO2 emissions during the cropping season. Thus, in this study, we studied the effects of tillage and cropping systems on C inputs and soil CO2 fluxes during three cropping seasons at three different sites in the Ebro River valley (northeast Spain). Carbon inputs ranged from 650 to 6000 kg ha–1 and seasonal average CO2 flux ranged from 0.10 to 1.76 g CO2 m–2 h–1. Differences in rainfall led to marked differences in C inputs and soil fluxes among growing seasons. Although differences among tillage treatments were weak, CO2 fluxes under NT were always lower. Intensification of cropping systems led to an increase in C input. A move from CT to NT together with cropping intensification is suitable to increase C inputs and to reduce soil CO2 fluxes in semiarid Mediterranean agroecosystems. ; This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL2001-2238-CO2-01 and AGL 2004-07763-C02-02) and the European Union (FEDER funds). The first author was awarded a FPI fellowship by the Spanish Ministry of Science and Education.

39 Pags.- 4 Tabls.- 4 Figs. The defintive version is available at: http://www.sciencedirect.com/science/journal/01678809 ; There is a strong need to identify the combination of tillage and N fertilization practices that reduce the amount of nitrous oxide (N2O) emissions while maintaining crop productivity in dryland Mediterranean areas. We measured the fluxes of N2O in two field experiments with 3 and 15 years since their establishment. In the long-term experiment, two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three mineral N fertilization rates (0, 60 and 120 kg N ha−1) were compared. In the short-term experiment, the same tillage systems (CT and NT) and three N fertilization doses (0, 75 and 150 kg N ha−1) and two types of fertilizers (mineral N and organic N with pig slurry) were compared. N2O emissions, water-filled pore space, soil mineral N content, grain yields, N-biomass inputs and soil total nitrogen (STN) stocks were quantified and the N2O yield-scaled ratio as kg of CO2 equivalents per kg of grain produced was calculated. In both experiments tillage treatments significantly affected the dynamics of N2O fluxes. Cumulative losses of N as N2O were similar between tillage treatments in the long-term field experiment. Contrarily, although not significant, cumulative N losses were about 35% greater under NT than CT in the short-term experiment. NT significantly increased the production of grain and the inputs of N to the soil as above-ground biomass in both experiments. Averaged across fertilizer treatments, CT emitted 0.362 and 0.104 kg CO2 equiv. kg grain−1 in the long-term and the short-term experiment, respectively, significantly more than NT that emitted 0.033 and 0.056 kg CO2 equiv. kg grain−1, respectively. Nitrogen fertilization rates did not affect the average N2O fluxes or the total N losses during the period of gas measurement in the long-term experiment. Contrarily, in the short-term experiment, N2O emissions increased with application rate for both mineral and organic fertilizers. The use of pig slurry increased grain production when compared with the mineral N treatment, thus reducing the yield-scaled emissions of N2O by 44%. Our results showed that in rainfed Mediterranean agroecosystems, the use of NT and pig slurry are effective means of yield-scaled N2O emissions reduction. ; D. Plaza-Bonilla was awarded with a FPU fellowship by the Spanish Ministry of Education. This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01/02), the Aragon Government and La Caixa (grant GA-LC-050/2011), the Department of Agriculture of the Catalonia Government (grant 2012 AGEC 00012) and the European Union (FEDER funds). ; Peer reviewed