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Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is a re-emerging disease, posing a threat to wheat production. In Spain, stem rust has been rarely detected since the 1970s, but infection was observed in wheat fields in 2018. We analysed six stem rust samples collected in Rota, Cádiz province and one from Monteagudo del Castillo, Teruel province. All the samples from Rota were typed as race TKTTF, whereas the sample from Monteagudo del Castillo, collected in a wheat field adjacent to barberry bushes, was typed as race TKHBK. This race has a unique and significant virulence combination that includes virulence to Sr31, Sr33, Sr53 and Sr59, and is avirulent to Rusty, a durum line developed for universal susceptibility to the wheat stem rust pathogen. TKHBK is the first race outside the Ug99 race group with virulence to Sr31 and the first known race with virulence to Sr59. Genotyping studies indicate that race TKHBK does not belong to the Ug99 or TKTTF race groups and constitutes a previously unknown lineage. Two hundred bread and durum wheat cultivars and breeding lines from Spain were evaluated against TKHBK, TKTTF, and six additional races. Resistance was observed to all the races evaluated. Molecular markers confirmed the presence of Sr7a, Sr24, Sr31, Sr38 and Sr57 in bread wheat, and Sr13 in durum wheat. The re-emergence of wheat stem rust in Spain and the occurrence of unique virulences underscore the need to continue surveying and monitoring this disease. info:eu-repo/semantics/acceptedVersion

Stem rust, caused by Puccinia graminis, is a destructive group of diseases. The patho - gen uses Berberis species as alternate hosts to complete its life cycle. B. vulgaris and the endemic species B. hispanica and B. garciae are present in Spain. The objective of this study was to investigate the functionality of the indigenous barberry as alternate hosts. Field surveys were conducted in 2018 and 2019 in Huesca, Teruel and Albacete provinces of Spain. Aecial samples on barberry were analysed via infection assays and DNA analysis. B. garciae was predominant in Huesca and Teruel provinces, often found in the field margins of cereal crops. Aecial infections on B. garciae were ob- served in May and uredinial infections on cereal crops in June. Scattered B. hispanica bushes were occasionally found near cereal crops in Albacete, where aecial infections on B. hispanica were observed in June when most cereal crops were mature. Infection assays using aeciospores resulted in stem rust infections on susceptible genotypes of wheat, barley, rye and oat, indicating the presence of the sexual cycle for P. graminis f. sp. tritici, f. sp. secalis and f. sp. avenae. Sequence analyses from aecial samples sup- ported this finding as well as the presence of Puccinia brachypodii. This study provides the first evidence that indigenous Berberis species play an active role in the sexual cycle of P. graminis under natural conditions in Spain The research was supported by the United States Department of Agriculture‐Agricultural Research Service, the Bill and Melinda Gates Foundation and the United Kingdom Department for International Development managed by Cornell University, USA, grant number: DGGW‐OPP1133199, and the State Research Agency (AEI), Spain, project PID2020‐118650RR‐C31. Thanks to Dr Fanny Álvaro for the initial observation and sampling of aecial infection on barberry. The assistance of Dr Joan Pedrol and Dr Rosario Fanlo (University of Lleida, Spain) in grass species identification is gratefully acknowledged. We thank the assistance of Amparo López Olmeda (Teruel Plant Health Service), Gloria Herrero Sánchez (Cereales Teruel Sociedad Cooperativa) and Vicente Lozano Herrera (farmer cereal producer). Meteorological data from the El Ballestero site (Albacete province) were kindly provided by Manuel Fernández. Data from surface cropping area of Aragón have been provided by Sección de estadística del Departamento de Agricultura, Ganadería y Medio Ambiente del Gobierno de Aragón (Silvia Quílez‐Domingo). The support of Daniel Gómez and Alberto Pastoriza (Herbarium curators in the Pyrenean Institute of Ecology, IPE‐CSIC, Jaca) is thankfully acknowledged. Technical assistance of Melissa Carter, Jerry Johnson and Kim‐Phuong Nguyen from USDA‐ARS is acknowledged. Dr Villegas acknowledges the contribution of the CERCA program (Generalitat de Catalunya, Spain).

The effect of no-tillage (NT) (zero tillage) versus conventional tillage (CT) has beenevaluated in rainfed conditions but has seldom been studied under irrigation, wheresoil sealing favours soil degradation. To contribute to this knowledge, this researchanalyses soil aggregate stability under disaggregation forces produced under irriga-tion (causing slaking and mechanical breakdown) and the susceptibility to soil sealingin soils cropped with irrigated maize. Soils were sampled from 0 to 2 and from 0 to5 cm before maize planting. Soil aggregate stability against both disaggregation pro-cesses was expressed by the mean weight diameter (MWD). Soil organic carbon(SOC) was evaluated in aggregates of different size fractions that remained after thedisaggregation processes. Soil sealing susceptibility was characterised by the satu-rated hydraulic conductivity. The results confirmed the high disruption effect of slak-ing and mechanical breakdown processes. The MWD under those processes was upto 50% smaller and the susceptibility to seal was about three times higher in the soilsunder CT than under NT. The results of the top 0–2 cm layer showed an aggregatestability against mechanical breakdown 30% smaller than the 0–5 cm layer, whichcould be due to the soil surface sealing caused by drop impact. Greater MWDs wererelated to higher SOC values in the aggregates, which were about 20% higher in thesoils under NT than under CT. Thus, NT represents an effective management in irri-gated soils, reducing soil sealing and helping to maintain greater aggregate stability insoil surface against the disaggregation forces caused by drop impact and wettingprocesses. This study was funded by MCIN/AEI/10.13039/501100011033 (Grant No. AGL2017-84529-C3-3-R) and ERAMSUS Programme (Grant : ERASMUS+mobility).

Aims The surface crust formed by the drop impact of rainfall and/or irrigation is a prevalent characteristic in many Mediterranean soils. However, the temporal variation of soil hydraulic properties induced by surface crust during the high-frequency irrigation has rarely been investigated. Methods Beerkan infiltration tests in conjunction with the BEST method were used to investigate the effects of surface crusting on the spatio-temporal variation of saturated soil hydraulic conductivity (Ks, mm s−1), sorptivity (S, mm s−0.5), mean pore size (r, mm), number of effective pores per unit area (N, m−2) in Agramunt, NE Spain. Results In response to autumn tillage, intensive tillage (IT) increased Ks and S due to higher r and N, but both declined after 60 days. Reduced tillage (RT), maintained comparable Ks and S values, despite having a lower N value. After the spring tillage, both IT and RT developed crusted layers, resulting in decreased Ks, S and N. Long-term no-tillage (NT) showed an increasing trend of Ks and S over time, except for the last sampling. Spatial variation (i.e., between the rows, B-row vs. within the row of crops, W-row) of Ks and S was found, and non-crusted soils (W-row) had consistently higher Ks and S than crusted soils (B-row). Conclusions Conservation tillage i.e., RT and NT improve the surface soil structure and reduce the risk of crust development. Surface cover by crops may help to prevent crust formation within the row of crops, improving soil hydraulic conductivity.

13 Pags.- 9 Figs.- 3 Tabls. © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license., The irrigation systems of the Ebro valley can lead to high N2O emissions. The effects that crop diversification, such as double-cropping in combination with conservation tillage and different N fertilizer ratios, has on soil N2O emissions have not been extensively studied in this region. The goal of this research was to measure N2O soil emissions and determine the tillage practices and N fertilization rates that provide the lowest emissions when combined with double-cropping systems. The work compared monocropping maize (MC) versus legume-maize double-cropping (DC) with two tillage systems (conventional tillage, CT; and no-tillage, NT), and three mineral N fertilization rates (zero, medium and high). Pea for grain (2019), vetch for green manure (2020), and vetch for forage (2021) were the legumes employed. The N2O emissions ranged from 0 to 15.5 mg N2O-N m−2 d−1 and were concentrated in the fertilization periods. Soil temperature and water filled pore space (WFPS) content significantly influenced soil N2O emissions. For both cropping systems, the conditions with the highest N2O emissions were soil temperatures above 20 °C and a WFPS of 50–60 %. The use of legumes facilitated reduced N fertilization in DC without affecting crop yield and led to reduced N2O emissions in this cropping system. DC reduced the emission factor (EF), which in all cases was lower than the default IPCC EF (1 %). With DC, a medium N fertilization rate produced similar yields to the high rate commonly applied by farmers, and also entailed lower N2O emissions. The no-tillage system, although producing higher levels of N2O, achieved lower yield-scaled N2O emissions due to greater crop yields. This work underlines the advantages of using double-cropping no-tillage systems combined with medium rates of N fertilization to reduce soil N2O emissions., This research work was financially supported by the Ministerio de Ciencia e Innovación of Spain (project AGL2017-84529-C3-3-R; PhD fellowship PRE2018-084610).

Gas diffusion can be used to quantify soil quality and structural development that is strongly affected by soil use and management practices. There is a lack of information about the quantitative effect of tillage combined with crop sequences on soil structure. This study aimed to quantify the effects of tillage and crop sequences on soil bulk density, gas diffusivity, air-filled porosity, and the resulting pore continuity and their dynamic during the cropping cycle. A total of 288 undisturbed soil samples were collected over two growing periods (2018–19 and 2019–20) on a long-term field experiment (~25 years old) in Agramunt, NE Spain. Three factors were investigated to observe their influence on the above-mentioned soil's physical characteristics: two tillage systems (intensive tillage, IT and no-tillage, NT), two crop sequences (short fallow-maize, FM; legume-maize, LM) and two positions (within the row of crops, W-row; between rows of crops, B-row). Soil gas diffusivity was measured at five different soil water matric potentials (SWMP) (−10, −50, −100, −333 and −1000 cm H2O). LM crop sequence showed greater air-filled porosity, macroporosity and gas diffusivity, as well as enhanced pore continuity, than FM, especially at W-row. No significant differences were observed for measured gas diffusivity between NT and IT systems though NT had lower air-filled porosity and macroporosity (> 30 µm) compared to IT. Soil under NT showed greater pore continuity, particularly among macropores and less blocked pores than IT at higher SWMP (−10 cm H2O) but no difference was observed at lower SWMP (−1000 cm H2O) regardless of crop sequence and position. Air-filled porosity and pore continuity changes between maize planting and harvesting were greater under IT than NT. During the legume growing seasons, IT showed comparable pore continuity values to NT. In LM crop sequence soil gas transport was favorably affected alleviating the negative effect of intensive tillage on soil structural degradation. Long-term NT also improved soil structure as indicated by higher continuity of macropores, despite a decrease in air-filled porosity and macroporosity, but did not significantly lower gas diffusivity. The authors thank the support given by Dr. Stefan Fenner, the visiting Ph.D. candidate Mehrdad Soranj, Prof. Concha Ramos, the field and laboratory technicians Carlos Cortés and Silvia Martí, and the farmer Xavier Penella. The authors gratefully acknowledge support for this research from the Research Spanish Agency (DISOSMED Project-AGL2017-84529-C3-R). Rasendra Talukder also sincerely acknowledges the fund provided by University of Lleida to support Ph.D. fellowship. Daniel Plaza-Bonilla is a Ramón y Cajal fellow (RYC-2018-024536-I) co-funded by AEI-MICIU and European Social Fund.

Soil hydraulic properties and pore continuity are important parameters of soil quality and may differ among tillage systems, crop rotations, and change over time. However, there are some contrasting results, depending on soil type, climate and cultivation history on the spatial and temporal variations. The objective of this study was to determine spatio-temporal dynamics of soil hydraulic properties and pore characteristics (i.e., pore volume, effective porosity, and continuity) on a silt loam long-term tillage field experiment, in Agramunt, NE Spain, during two cropping years. Undisturbed soil samples were used to determine soil water retention, θ(Ψ), and soil hydraulic conductivity, K(Ψ), curves in two different tillage systems (intensive tillage, IT vs no-tillage, NT), two crop sequences (short fallow-maize, FM vs legume-maize, LM) and two positions (within the row of crops, W-row vs between the rows of crops, B-row). The results revealed that LM had greater specific hydraulic conductivity, Kpc in its macroporosity (>1000 µm) than FM due to greater number of effective pores, Npc and effective porosity, εpc. Soil water content, θ was greater under IT than under NT at higher soil water matric potential, Ψ (≥-3 cm H2O), whilst the opposite was observed at lower Ψ (≤ − 50 cm H2O). Long-term NT showed greater hydraulic conductivity, K at higher Ψ (≥ − 10 cm H2O) than IT, and no difference at lower Ψ. Although IT had greater pore volume, ϕpc than NT in the macroporosity and coarse mesoporosity (1000–60 µm) pore size classes, NT had two times greater Kpc than IT due to increased Npc, εpc, and pore continuity, Cwpc. K(Ψ) and pore characteristics showed spatial variations (W-row vs B-row). W-row had significantly greater K at higher Ψ (≥ − 3 cm H2O) than B-row. Temporal dynamics of soil hydraulic properties and pore characteristics were not evident under IT during crop succession. This study shows that LM increases specific hydraulic conductivity of soil macroporosity by increasing the number of effective macropores and the effective porosity. In a Mediterranean climate, this may improve the hydrological functions of agricultural soil and associated crop yield. Further, long-term NT formed a stable number of effective macropores and coarse mesopores, and showed a greater pore continuity in coarse and fine mesopores, resulting in improved soil water flux. The authors thank the support given by Dr. Stefan Fenner, the visiting Ph.D. candidate Mehrdad Soranj, Prof. Concha Ramos, the field and laboratory technicians Carlos Cortés and Silvia Martí, and the farmer Xavier Penella. The authors gratefully acknowledge support for this research from the Research Spanish Agency (DISOSMED Project - AGL2017-84529-C3-R). Rasendra Talukder also sincerely acknowledges the fund provided by University of Lleida to support its PhD fellowship. Daniel Plaza-Bonilla is Ramón y Cajal fellow (RYC-2018-024536-I) co-funded by MICIN/AEI/10.13039/501100011033 and European Social Fund.

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Adequate fertilization strategies are paramount to fulfill increasing demands for food, feed and fiber while reducing environmental impacts. However, their optimization under Mediterranean no-till systems has received little attention. The objective of this work was to assess winter cereal yield and water and N use efficiencies in a rainfed semiarid Mediterranean climate under (i) a range of pre-plant fertilizers [control without N fertilizer (0 N), and the following at 75 kg N ha−1: mineral N (MIN), swine slurry (SS), poultry manure (PM), and compost (COM)], (ii) fertilizer incorporation: no-tillage without incorporating (NT) or incorporation with a vibrocultivator (INC) and (iii) application of urea-ammonium nitrate solution (UAN) as top-dress as a control without UAN (UAN-) or 50 kg N ha−1 (UAN+). The experiment covered six cropping seasons (2012–2019). Pre-plant applications had similar responses in crop yield, biomass, N uptake, grain N, water-use efficiency for biomass (WUEb), and water-use efficiency for yield (WUEy) but were greater than 0 N. The lack of differences between pre-plant fertilizers would be explained by the high amount of residual N and the mineralized N during the crop cycle. Top-dress UAN increased WUEy and crop yield in all the cropping seasons by an average of 587 kg grain ha−1, which represented 18 % of the total annual production. Averaged across variables and the growing seasons, INC reduced soil water content and WUEb by 10 % (from 24.3 to 21.8 kg ha−1 mm−1). Also, INC reduced grain yield by 9% (from 3799 to 3450 kg ha−1) by reducing the number of spikes m-2 produced, pointing out that INC resulted in water deficit during the early reproductive period of the crop. While INC is often consider a best management practice to reduce NH3 volatilization losses from broadcast fertilizer applications, the results demonstrate that in rainfed Mediterranean agroecosystems water is more limiting than the N that could be potentially lost by volatilization.

6 Pags.- 5 Figs.- 2 Tabls. © The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license., In croplands, the adoption of certain management practices may increase soil organic carbon (SOC) levels. In this study, we evaluated the short-term impact of crop stover management and the interaction between crop stover and irrigation method on SOC change in a continuous maize (Zea mays L.) system in Spain. Four years after the beginning of the experiment, total SOC and C fractions (particulate organic matter carbon, POM-C; and mineral-associated organic matter carbon, Min-C) contents, SOC stocks and SOC stock changes were measured in four different soil layers (0−5, 5−10, 10−25 and 25−50 cm) in an experiment with two irrigation methods (sprinkler and flood) and three stover management systems (conventional tillage with all the stover incorporated, CT; no-tillage maintaining the stover, NTr; and no-tillage removing the stover, NT). Stover management resulted in significant differences in SOC and POM-C but not in Min-C. In particular, NT reduced SOC and POM-C contents compared with CT and NTr (about 10 and 60 %, respectively). After 4 years, SOC change was not affected by the interaction between stover management and irrigation. Concurrently, both CT and NT showed SOC losses, reaching 0.11 and 1.22 Mg ha−1 yr−1 in CT and NT, respectively. However, NTr showed SOC gains at a rate of 0.09 Mg ha−1 yr−1. Consequently, the removal of crop stover has been demonstrated as a detrimental strategy to store SOC in the short-term in irrigated continuous maize systems., Financial support of the Ministry of Economy and Competitiveness of Spain (Grant AGL2013-49062-C4-4-R), the Spanish State Agency for Research (AEI) (Grant AGL2017-84529-C3-1-R) and the European Union (FEDER funds) is gratefully acknowledged.

42 Pags.- 5 Tabls.- 4 Figs. © 2020 The Authors. Soil Science Society of America Journal © 2020 Soil Science Society of America, The aim of this study was to evaluate the impact of 21 years of tillage and N fertilization and the conversion from a rainfed to an irrigated cropping system on soil organic C (SOC). The study was carried out in northeastern Spain in a long‐term tillage and N rate field experiment established in 1996 under barley rainfed conditions, which in 2015 was converted into irrigation with corn. Three types of tillage (conventional tillage, CT; reduced tillage, RT; no‐tillage, NT) and three mineral N fertilization rates (0, 60, and 120 kg N ha−1 under barley, and 0, 200, and 400 kg N ha−1 under corn) were compared. Annual C‐inputs as aboveground crop residues and annual SOC sequestration rate (∆SOCrate) (0–40 cm depth) were calculated in three different periods (P1, P2 and P3) under rainfed (‐R) and irrigated (‐I) conditions (P1‐R, from 1996 to 2009; P2‐R, from 2009 to 2015; P3‐I, from 2015 to 2017). At the end of P3‐I, particulate organic C (POC) was measured from the 0–5, 5–10, 10–20, 20–30, and 30–40 cm depths. Averaged over all treatments, ∆SOCrate was 492, 222, and 969 kg C ha−1 yr−1 for P1‐R, P2‐R, and P3‐I, respectively. In P1‐R and P3‐I, C‐input explained 70% of the variability of ∆SOCrate. In P1‐R, ∆SOCrate followed the order NT > RT > CT, while for N rate, order was high > medium > 0. In P3‐I at the highest N rate, ∆SOCrate followed the order NT > RT > CT. In P2‐R, ∆SOCrate did not show differences between tillage and/or N rate treatments. The increase in SOC after conversion from a rainfed to an irrigation system was mainly explained by POC, which was increased by 75% compared to the previous rainfed period. The modification of the cropping system through the introduction of irrigation and adequate crop management practices under no‐tillage and adjusted N fertilizer rates can contribute to the sequestration of large amounts of atmospheric CO2., This research work was financially supported by the Ministerio de Economía y Competitividad of Spain (project AGL2013-49062-C4-1-R; PhD fellowship BES‐2014‐070039). DPB received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (IJCI-2016-27784) and is Ramón y Cajal fellow (RYC2018-024536-I) of the Ministerio de Ciencia, Innovacion y Universidades.

Irrigation and soil management can impact soil nitrous oxide (NO) emissions. Flood and sprinkler irrigation systems together with conventional tillage are the main practices used in the high yielding maize systems in Mediterranean Spain. The objective of this field work was to quantify the effect of the irrigation system (i.e., flood, F; and sprinkler, S) and the soil tillage system (i.e., conventional tillage, CT; no-tillage maintaining the maize stover, NTr; and no-tillage removing the maize stover, NT) on the NO emissions from the soil during 3 yr (2015, 2016, and 2017). S irrigation, with mean values of 1.35 kg NO-N ha yr throughout the 3 yr, obtained 42% lower NO emissions than F irrigation. On average of the three growing seasons, yield-scaled NO emissions by grain yield and by grain N uptake in F irrigation were two-fold higher than in S irrigation. Moreover, in one out of three growing seasons (2017), no-tillage systems (i.e., NTr and NT) showed greater yield-scaled NO emissions compared with CT. The higher maize grain yield with the S irrigation compared to F irrigation, as well as the lower NO emissions reported under S irrigation resulted in the reduction of the yield-scaled NO emissions. Our findings highlight the role of sprinkler irrigation decreasing NO emissions in comparison to flood irrigation in Mediterranean agroecosystems., Samuel Franco-Luesma was awarded a FPI fellowship by the Ministerio de Economia y Competitividad of Spain (PhD fellowship BES-2014-069175). Daniel Plaza-Bonilla was awarded Juan de la Cierva postdoctoralgrants from the Ministerio de Economía y Competitividad of Spain (refs. FJCI-2014-19570; IJCI-2016-27784). This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL2013-49062-C4-4-R). This paper has been produced within the context of theRed SIRENA network (Ref. AGL2015-68881-REDT) fundedby the Ministerio de Economiìa y Competitividad of Spain.

47 pags.- 6 Tabls.- 5 Figs. The definitive version is available at: https://www.sciencedirect.com/science/journal/0308521X, Agriculture contributes to a significant proportion of global emissions of greenhouse gases (GHG) but can also participate in climate change mitigation. The introduction of legumes in crop rotations reduces the dependence on N fertilizers and may mitigate the carbon (C) footprint of cropping systems. The aim of this study was to quantify the C footprint of six low-input arable cropping systems resulting from the combination of three levels of grain legumes introduction in a 3-yr rotation (GL0: no grain legumes, GL1: 1 grain legume, GL2: 2 grain legumes) and the use of cover crops (CC) or bare fallow (BF) between cash crops, covering two rotation cycles (6 years). The approach considered external emissions, on-site emissions and soil organic carbon (SOC) stock changes, and prioritized (i) field observations and (ii) simulation of non-measured variables with the STICS model, rather than default emission factors. As expected, fertilizers accounted for 80–90% of external emissions, being reduced by 50% and 102% with grain legumes introduction in GL1-BF and GL2-BF, compared to the cereal-based rotation (GL0-BF). Cover crops management increased machinery emissions by 24–35% compared to BF. Soil nitrous oxide (N2O) emissions were low, ranging between 205 and 333 kg CO2 eq. ha−1 yr−1 in GL1-BF and GL0-BF, respectively. Nitrate leaching represented the indirect emission of 11.6 to 27.2 kg CO2 eq. ha−1 yr−1 in the BF treatments and 8.2 to 10.7 kg CO2 eq. ha−1 yr−1 in the CC treatments. Indirect emissions due to ammonia volatilization ranged between 8.4 and 41.8 kg CO2 eq. ha−1 yr−1. The introduction of grain legumes strongly influenced SOC changes and, consequently, the C footprint. In the BF systems, grain legumes introduction in the rotations led to a significant increase in the C footprint, because of higher SOC losses. Contrarily, the use of cover crops mitigated SOC losses, and lowered the C footprint. These results indicated the need of CC when increasing the number of grain legumes in cereal-based rotations. Despite the multiple known benefits of introducing grain legumes in cropping systems our research highlights the need to consider soil organic carbon changes in environmental assessments., This research was supported by (i) the FP6 Grain Legumes Integrated Project (food-CT-2004-506223), (ii) the European Commission (REA) through the LEGATO project (FP7-613551) and (iii) the French National Research Agency (ANR) through the LEGITIMES French project (ANR-13-AGRO-0004). It also benefited from the support of the Climate-CAFE European project, which was selected by the European FACCE-JPI ERA-NET Plus program. INS was funded thanks to a convention between the University of Lleida and INRA-Toulouse. DPB received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (IJCI-2016-27784).

28 Pags.- 3 Figs., Major constraints to rainfed production systems in the world’s drylands include low and highly variable rainfall, nutrient deficiencies and land degradation by wind and water erosion. Although the same principles to cope with these limitations could be in theory applied to all dryland situations, there is no a universal recipe for sustainable dryland agriculture. In this chapter, the authors recall some of the challenges that have been identified for semiarid rainfed farming systems, namely soil conservation, water use efficiency, nutrient use efficiency and climate change mitigation, as well as some sustainable cropping and management strategies that have been formulated and recommended to address them appropriately. To this end, the authors provide examples supporting those practices mainly from semiarid Mediterranean agroecosystems. Among all the strategies discussed in this Chapter, and despite their limitations, the maintenance of a protective crop residue cover and the reduction of tillage operations appear to be the simplest technological options not only to control soil erosion but also to improve water and nutrient use efficiency and mitigate greenhouse gas emissions. The authors conclude that sustainable agricultural management in drylands should be primarily based on conservation agriculture practices and associated local-based crop residue management systems.

In irrigated Mediterranean conditions there is a lack of knowledge about the best combination of tillage and N fertilization practices to reduce soil nitrous oxide (N2O) emissions while maintaining maize productivity. The aim of this work was to investigate the effects of different soil management practices and synthetic N fertilization rates on soil N2O emissions and their relationship with maize grain yield to determine the best management system to reduce yield-scaled N2O emissions (YSNE) in a semiarid area recently converted to irrigation under Mediterranean conditions. A long-term tillage and N rate field experiment established in 1996 under barley (Hordeum vulgare L.) rainfed conditions, was converted to irrigated maize (Zea mays L.) in 2015. After the transformation to irrigation, the field experiment maintained the same tillage treatments and N fertilization rates. Three types of tillage (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) and three mineral N fertilization rates (0, 200, 400 kg N ha−1) were compared during three years (2015–2017) in a randomized block design with three replications. Soil N2O emissions, water-filled pore space, soil temperature, mineral N content (as NH4+ and NO3−), denitrification potential and maize grain yield and above-ground N uptake were quantified. Moreover, the emission factor (EF) and YSNE were calculated. The results showed that the combination of NT and the highest rate of N fertilization led to greater N2O emissions. Furthermore, the lowest N2O fluxes were observed in CT when WFPS was below 40% and the highest N2O fluxes were seen in NT when WFPS was above 60% coinciding with the greatest denitrification potential. Cumulative N2O emissions in 2017 and 2015 followed the order 400 > 200 > 0 kg N ha−1, while in 2016, rate of 400 and 200 kg N ha−1 showed greater cumulative N2O emission compared to the control. Only RT showed differences between growing seasons on cumulative N2O emissions, with greater values in 2017 compared to 2015, and intermediate values in 2016. In all treatments, the N2O EF was much lower than the default IPCC emission factor (1%). NT and RT increased the grain production compared to CT which was affected by severe soil crusting causing water deficit. Likewise, N fertilizer treatments significantly affected the YSNE, increasing with increasing fertilizer N application rate in the first year of study. Our data show that the use of NT or RT does not lead to more yield-scaled N2O emissions than CT in Mediterranean agroecosystems recently converted to irrigation., This research work was financially supported by the Ministerio de Economía y Competitividad of Spain (project AGL2013-49062-C4-1-R; PhD fellowship BES‐2014‐070039). DPB received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (IJCI-2016-27784).

11 Pags.- 2 Tabls.- 7 Figs., Mediterranean rainfed areas are transformed into irrigation to stabilize or increase crop yields. The gradual occupation of irrigation leads to an increase in nitrogen use and intensity of tillage. The aim of this work was to evaluate the combined impact of tillage systems and mineral N fertilization rates on maize grain yield, water and nitrogen use efficiencies (WUE and NUE) under Mediterranean irrigated conditions. The study was carried out in NE Spain during three maize growing seasons (i.e. years 2015, 2016 and 2017). A long-term (LTE) tillage and N rate field experiment established in 1996 under rainfed conditions was transformed into irrigation with maize (Zea mays L.) monocrop as cropping system in 2015. Three types of tillage (conventional tillage, CT; reduced tillage, RT; no-tillage, NT) and three mineral N fertilization rates (0, 200, 400 kg N ha−1) were compared. In 2015, an adjacent experiment (short-term experiment, STE) with the same layout was set up in an area previously managed under long-term rainfed NT for the last 21 years. In the long-term tillage and N fertilization combination (LTE), the reduction of tillage (NT and RT) led to greater grain yield when applying 200 and 400 kg N ha−1 compared to the use of the same rates under CT. Differently, in the sort-term experiment with preceding NT (STE), tillage systems did not influence grain yields, while N application led to greater yields than the control (0 kg N ha−1). In both situations (LTE and STE), NT and RT enhanced soil water content before planting leading to greater crop growth compared to CT. The lack of available water under CT caused lower maize stover, yield, and yield components in LTE and, therefore, lower WUEB (for biomass) and WUEY (for yield). In LTE, the use of long-term CT led to a significant accumulation of nitrate compared to NT. Differently, in the STE, soil nitrate content did not show differences between tillage systems. In the LTE, water and N were used more efficiently to produce aboveground biomass and grain yield in RT and NT. Our study shows that in Mediterranean agroecosystems transformed into irrigation the use of NT and RT with medium rates of N leads to greater maize yield, WUE and NUE than the traditional management based on CT with high rates of mineral N. In rainfed areas with long-term history of no-till, this soil management system can be successfully maintained if transformed into irrigation., This research work was financially supported by the Ministerio de Economía y Competitividad of Spain (project AGL2013-49062-C4-1-R; PhD fellowship BES‐2014‐070039). DPB received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (IJCI-2016-27784).

Tillage and organic fertilization impact short-term soil CO2 fluxes. However, the interactive effect of these two management practices has been rarely studied under field conditions. The objective of this study was to evaluate the impact of tillage (NT, no-tillage, and CT, conventional tillage) and fertilization strategy (PS, pig slurry, and MF, mineral fertilizer) on short-term soil CO2 fluxes in a rainfed Mediterranean agroecosystem. Soil CO2 fluxes were measured several times during two tillage and pre-sowing fertilization periods in 2012 and 2013 (7 and 6 times in 2012 and 2013, respectively). In the two years studied, tillage and fertilization significantly affected soil CO2 fluxes, but the interaction between both factors was not significant. The application of PS resulted in a sharp and immediate increase in the soil CO2 flux. One hour after the application of the organic fertilizer, soil CO2 emissions increased from 0.05 to 0.70 g CO2 m−2 h−1 and from 0.08 to 0.82 g CO2 m−2 h−1 in 2012 and 2013, respectively. Unlike fertilization, 1 h after tillage similar soil CO2 fluxes were observed in CT and NT plots. However, after 7 h, larger fluxes were observed in CT compared with NT in both years. Cumulative CO2 flux during the first 24 h after fertilization and tillage was about three- and two-fold greater in PS than in MF and in CT than in NT, respectively. The results of this study showed that in rainfed Mediterranean systems, soil management and fertilization have a noteworthy impact on short-term soil CO2 losses though no interactive effects were observed between both management practices., This research was supported by the Ministry of Economy and Competitiveness of Spain (AGL2010-22050-C03-01/02; AGL2013-49062- C4-4-R) and the COMET-Global project (FACCE-JPI grant).

Carolight® is a transgenic maize variety that accumulates extraordinary levels of carotenoids, including those with vitamin A activity. The development of Carolight® maize involved the technical implementation of a novel combinatorial transformation method, followed by rigorous testing for transgene expression and the accumulation of different carotenoid molecules. Carolight® was envisaged as a way to improve the nutritional health of human populations that cannot access a diverse diet, but this ultimate humanitarian application can only be achieved after extensive testing for safety, agronomic performance and nutritional sufficiency. In this article, we chart the history of Carolight® maize focusing on its development, extensive field testing for agronomic performance and resistance to pests and pathogens, and feeding trials to analyze its impact on farm animals (and their meat/dairy products) as well as animal models of human diseases. We also describe more advanced versions of Carolight® endowed with pest-resistance traits, and other carotenoid-enhanced maize varieties originating from the same series of initial transformation experiments. Finally we discuss the further steps required before Carolight® can fulfil its humanitarian objectives, including the intellectual property and regulatory constraints that lie in its path. European Research Council Advanced Grant (BIOFORCE) and Proof of Concept Grant (Multinutrient Maize) to PC; Spanish Ministry of Economy and Competitiveness (AGL2014-53970-C2-1-R, AGL2015-65846-R, BIO2014-54426-P and BIO2014-54441-P); RecerCaixa project PC084082; Catalan Autonomous Community 2014 SGR 1296 Agricultural Biotechnology Research Group and Agrotecnio Research Center. JDG thanks the UdL for a Ph.D. fellowship.

39 Pags.- 5 Tabls.- 5 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03784290, Tillage and N fertilization strategies including mineral and organic sources need to be studied in combination given their importance on the production cost that farmers face and their potential interaction on crop performance. A four-year (2010–2014) experiment based on barley monocropping was carried out in NE Spain in a typical rainfed Mediterranean area. Two tillage treatments (CT, conventional tillage; NT, no-tillage) and three rates of N fertilization (0; 75 kg N ha−1, applied at top-dressing; 150 kg N ha−1, applied at pre-sowing and at top-dressing at equal rate), with two types of fertilizers (ammonium-based mineral fertilizer and organic fertilizer with pig slurry), were compared in a randomized block design with three replications. Different soil (water and nitrate contents) and crop (above-ground biomass, grain yield, yield components and N concentration in biomass and grain) measurements were performed. Water- and nitrogen use efficiencies (WUE and NUE) as well as other N-related indexes (grain and above-ground biomass N uptake; NHI, nitrogen harvest index; NAR, apparent nitrogen recovery efficiency) were calculated. Barley above-ground biomass and grain yield were highly variable and depended on the rainfall received on each cropping season (ranging between 280 mm and 537 mm). Tillage and N fertilization treatments affected barley grain yields. No-tillage showed 1.0, 1.7 and 6.3 times greater grain yield than CT in three of the four cropping seasons as a result of the greater soil water storage until tillering. Water scarcity during the definition of the number of spikes per m2 under CT would have compromised the compensation mechanism of the other two yield components. Pig slurry application led to the same (3 of 4 years) or higher (1 of 4 years) grain yield than an equivalent rate of mineral N fertilizer. Regardless the N origin, barley yield did not respond to the application of 150 kg N ha−1 split between pre-sowing and top-dressing compared to the 75 kg N ha−1 rate applied as top-dressing. A significant nitrate accumulation in the soil over the experimental period was observed under CT. Greater barley water use efficiency for yield (WUEy), N uptake and grain N content were found under NT than CT in three of the four cropping seasons studied. Moreover, for a given N rate, the use of organic fertilization increased significantly the WUEy as an average of CT and NT. When CT was used, a greater NHI was observed when using pig slurry compared with mineral N as an average of the four years studied. However, the use of different N fertilization treatments (rates or types) under CT or NT did not increase the NUE compared with the control. Our study demonstrates that the use of NT and the application of agronomic rates of N as pig slurry leads to greater barley yield and water- and nitrogen-use efficiencies than the traditional management based on CT and mineral N fertilization., Daniel Plaza-Bonilla received a Juan de la Cierva Postdoctoral Grant from the Ministerio de Economía y Competitividad of Spain. This research was supported by the Ministerio de Economía y Competitividad of Spain (grants AGL2007-66320-C02-01, AGL2010-22050-C03-01/02 and AGL2013-49062-C4). This paper has been produced within the context of the Red SIRENA network (Ref. AGL2015-68881-REDT) funded by the Ministerio de Economía y Competitividad of Spain.

49 Pags.- 5 Tabls.- 6 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01671987, The aim of this study was to determine the most appropriate soil management to reduce the structural degradation of soils susceptible to crusting in Mediterranean areas recently transformed into irrigation. A long-term field experiment (LTE) under rainfed conditions was established in 1996 in NE Spain to compare three tillage systems (no-tillage, NT; reduced tillage, RT; conventional tillage, CT). The experiment was transformed to irrigated corn in 2015. In 2015, an adjacent experiment with the same layout was created (short-term experiment, STE) in an area previously managed under long-term NT. The study was carried out during the second corn growing season (i.e. year 2016). Soil samples were collected from 0 to 5 cm depth at different dates during corn season. Dry and water-stable macroaggregates and their C concentration, soil organic carbon (SOC) and labile C concentration, soil respiration, bulk density, penetration resistance (PR), water infiltration, macroporosity, microporosity, amount of crop residues and ground cover, corn development, aerial biomass, and grain yield were measured. In LTE and STE tillage led to a breakdown of dry sieved aggregates (of 2–4 and 4–8 mm size) in RT and CT, being slowly reconsolidated throughout the corn growing season. However, macroaggregate water-stability did not increase in CT and RT compared to NT due to a lower SOC concentration, making the soil more susceptible to its degradation by the action of water. SOC differences between treatments were more pronounced in LTE than STE given the long-term differential management in the first, which allowed greater accumulation of SOC under NT. In LTE, PR between corn rows was greater under NT than CT and RT and non-significantly different between treatments within the row. In the case of STE, PR increased over time after tillage (CT and RT) to match NT in the last sampling. Crop establishment was slower in CT than NT in LTE highlighting the impact of soil surface degradation on crop development. However, contrarily to the differences in corn yield in 2015, a careful planting in 2016 led to a lack of differences between tillage systems on corn yield. Our results indicate that in areas transformed into irrigation intensive tillage leads to greater susceptibility to soil structural degradation. Thus, in these areas the adoption of conservation agriculture practices such RT and NT enhances soil resilience to degradation processes and ensures an adequate development of the crop., This research work is financially supported by the Ministerio de Economía y Competitividad of Spain (project AGL2013-49062-C4-1-R; PhD fellowship BES‐2014‐070039). Daniel Plaza-Bonilla received a Juan de la Cierva postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (FJCI-2014-19570).

36 Pags.- 2 Tabls.- 4 Figs. The definitive version is available at: https://dl.sciencesocieties.org/publications/aj, The effect of delaying sowing date and maturity class on no-till (NT) winter cereal performance was studied over two periods of 3 yr each. A 3 (sowing date) × 2 (maturity class) randomized complete block design was run for 3 yr with barley (Hordeum vulgare L.) (B-) (2006–2007 to 2008–2009) and soft wheat (Triticum sp.) (W-) (2009–2010 to 2011–2012) in northeastern Spain. Sowing dates corresponded to October (D1- the standard farming practice), November (D2), and December (D3). Maturity classes corresponded to early (-EC) and medium (-MC). Crop aboveground biomass, grain yield, and yield components were analyzed. The water use efficiency of aboveground biomass (WUEb) and grain yield (WUEy), and nitrogen use efficiency (NUE), were calculated. Averaging barley maturity classes and cropping seasons, D2 and D3 increased their grain yields 59 and 46%, respectively, when compared to D1. A greater number of grains per spike, as well as higher WUEb and NUE were observed in D2 and D3 compared to D1 in two of the three barley seasons. A greater thousand kernel weight (TKW) and higher WUEy were observed when sowing was delayed. Averaged across years, WEC presented a greater yield and aboveground biomass for D2 and D3 compared to D1, while for WMC there were no grain yield differences seen between the sowing dates, aboveground biomass or yield components. Our results demonstrate that, in western Mediterranean areas, sowing delay under NT can increase grain yield, WUE and NUE of winter barley, and also of wheat but only during wet years., This work was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Project Grants AGL2007-66320-C02-01/AGR and AGL2010-22050-C03-01). Daniel Plaza-Bonilla received a “Juan de la Cierva-Formación” postdoctoral grant from the Ministerio de Economía y Competitividad of Spain (ref. FJCI-2014-19570).

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).

44 Pags.- 5 Tabls.- 7 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809, 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).

24 Pags., 4 Tabls, 3 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/00167061, Low-intensity soil management systems like no-tillage (NT) are being increasingly accepted as an essential part of sustainable farming systems. The objective of this work was to study the effects of NT maintenance over time on soil aggregation and soil organic carbon (SOC) protection on a semiarid Mediterranean agroecosystem. A NT chronosequence was established with five phases: (i) conventional tillage (CT); (ii) NT for 1 year (NT-1); (iii) NT for 4 years (NT-4); (iv) NT for 11 years (NT-11) and (v) NT for 20 years (NT-20). N fertilization was based on pig slurry for the whole experimental area. Soil samples were collected from four depths (i.e., 0–5, 5–10, 10–20, 20–30 cm). Dry and water-stable aggregates, SOC concentration and C concentration of water-stable aggregates were measured. SOC concentration reached its maximum value after 11 years under NT. However, the differences between NT phases were only found in the 0–5 cm soil depth. In soil surface (i.e., 0–5 cm), water-stable large macroaggregates (2–8 mm) were 0.02, 0.12, 0.32 and 0.31 g g− 1 dry soil for the NT-1, NT-4, NT-11 and NT-20 phases, respectively. C concentration of microaggregates increased in relation with the number of years under NT. SOC and water-stable macroaggregate stratification were greatest with the increase in the years under NT, emphasizing the close relationship between SOC and aggregation. In Mediterranean semiarid agroecosystems, the increase in the proportion of stable macroaggregates and the enrichment of C concentration within microaggregates are two main mechanisms of SOC protection when NT is maintained over time., This research was supported by the Comision Interministerial de Ciencia y Tecnologia of Spain (AGL 2004-07763-C02-02 and AGL 2010-22050-C03-01). D. Plaza-Bonilla was awarded with a FPU fellowship by the Spanish Ministry of Education. Jorge Álvaro-Fuentes acknowledges the Consejo Superior de Investigaciones Científicas (CSIC) for his contract within the “Junta para la Ampliación de Estudios” (JAE-DOC) programme co-financed by the European Social Fund.

37 Pags.- 6 Tabls.- 5 Figs. The definitive version is available at: https://dl.sciencesocieties.org/publications/sssaj, 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., 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) 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.

43 Pags.- 3 Tabls.- 8 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/11610301, In this work, appropriate management practices for crop production under the variable climate conditions of the Mediterranean region, in particular rainfall, were tested with the use of a modelling system applied to long-term (i.e. 18 years) field data. The calibration of the CropSyst model was performed using data collected from 1996 to 1999 at three different Mediterranean locations (i.e., HYP-Guissona, MYP-Agramunt and LYP-Candasnos, i.e. high, medium and low yield potential, respectively) within a degree of yield potential. The model simulated reasonably well barley growth and yield to different tillage and N fertilization strategies. Simulations of barley performance over 50 years with generated weather data showed that yields were often greater and never smaller under no-tillage compared to conventional tillage with a mean increase of 36%, 63% and 18% for HYP-Guissona, MYP-Agramunt and LYP-Candasnos. In MYP-Agramunt, the long-term data showed a 40% increase in grain yields when using no-tillage compared to conventional tillage, as an average of 18 years. The model also predicted that greater N applications in no-tillage were appropriate to take advantage of additional water supply. Taking into account the limited amount of soil water available, overall N fertilizer applications could be reduced to about half of the traditional rate applied by the farmers without yield loss. The 50-yr simulation, confirmed by the long-term experimental data, identified no-tillage as the most appropriate tillage practice for the rainfed Mediterranean areas. Also, N fertilization must be reduced significantly when tillage is used or when increasing aridity. Our work demonstrates the usefulness of the combination of long-term field experimentation and modelling as a tool to identify the best agricultural management practices. It also highlights the importance of posterior analysis with long-term observed field data to determine the performance of simulation results., This work was funded by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of the Spanish National Plan of Research, projects AGR94-198, AGF98-0261-C02, AGL2001-2238-CO2-02, AGL2004-07763-CO2-01-AG, AGL2007-66320-C02-C02-01/AGR, AGL2010-22050-C03-01 and the Instituto Nacional de Investigaciones Agrarias (INIA), project PD96-029. We also thank the Ministry of Education and Culture, which funded the doctorate studies of P. Angás. Daniel Plaza-Bonilla received a “Juan de la Cierva” grant from the Ministerio de Economía y Competitividad of Spain.

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.

The adoption of no-tillage systems in semi-arid cereal fields in northern Europe has resulted in difficulties in controlling Bromus diandrus. However, in some fields, lower densities are observed in continuous long-term no-tillage management than in other reduced tillage systems. A cumulative effect on the seedbank could promote changes in the period of seedling emergence and in population demography. This study evaluated the effect of long-term mouldboard plough (MbP), chisel plough (ChP), subsoiler (SS) and no-tillage (NT) on the population dynamics of B. diandrus. The work was carried out in a barley (Hordeum vulgare)-wheat (Triticum aestivum)-barley rotation during three seasons where these soil management systems had been applied for the last 22 years. Cumulative emergence (CE) and densities of B. diandrus followed a gradient of ChP > SS > NT > MbP. This cumulative effect over time resulted in significant differences in population demography. A previous hydrothermal emergence model developed for this species estimated the percentage of emergence prior to the date of sowing to be: 71%, 92% and 53% for the seasons 2008-2009, 2009-2010 and 2010-2011 respectively. Furthermore, the reduction in CE observed was on average 53% in SS, 92% in NT and 98% in MbP in comparison with that recorded in ChP. The long-term effect of different tillage systems tended to cause changes to soil characteristics (photo-inhibition of germination, soil temperature, water availability) affecting B. diandrus demography, reaching equilibrium in weed densities over years, which were significantly lower in MbP and NT than in ChP or SS This work was supported by two projects of the Plan Nacional I +D + I of the Spanish Ministry of Science and Education (AGL2007-60828 and AGL2010-22084-C02-01), and the second author obtained a PhD grant from the Universitat de Lleida. Special thanks to Cristina Majan, Noemı Pacheco, Laura Rosell and Nuria Moix for their help during the data collection in the field and to Jaume Gregori and Carlos Cortes for their help in the field work.

11 Pag., 7 Tabl., 8 Fig., The response of soil CO2 flux to long-term tillage practices (no-tillage, NT; minimum tillage, MT; conventional tillage, CT) and N fertilization level (zero; medium, 60 kg N ha−1; high, 120 kg N ha−1) was studied during three growing season in a rainfed Mediterranean agroecosystem. Soil CO2 flux was related to the crop growth, with the highest flux during spring (i.e., March–May). Tillage and N fertilization effects on soil CO2 flux during growing seasons depended on weather conditions: greater soil CO2 flux under MT and NT on dry years, greater under CT and MT on a wet year. Nitrogen fertilization affected soil CO2 flux during this wet growing season: flux with N fertilizer additions was higher than flux on the unfertilized plots. Thirteen years after establishment of the experiment, the soil organic carbon (SOC) stock under long-term NT was 3.9 Mg C ha−1 greater than under CT and 4.3 Mg C ha−1 greater than under MT. The SOC stocks with N fertilizer additions were 4 Mg C ha−1 greater than the stock on unfertilized plots. The increase of C inputs with N fertilization was more pronounced under NT than under MT or CT. For this reason the increased response of SOC stock to N fertilization is expected under NT in a longer period of time. The product between soil water content and soil temperature explained between 75 and 94% of the seasonal variability of soil CO2 flux. However, soil CO2 flux and SOC stock were hardly related., This work was supported by the Comision Interministerial de Ciencia y Tecnologia of Spain (Grants AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR). F.J. Morell received a grant for his doctorate studies from the Spanish Ministry of Science and Innovation.

7 Pags.- 6 Figs.- 1 Tabl., The response of soil CO2 flux to tillage operations and rainfall events was studied under semiarid Mediterranean conditions. The study was conducted on a barley monoculture agro-ecosystem during summer/autumn fallow periods in four consecutive years (2005–2008). The study compared three N fertilization levels (zero, medium; 60 kg N ha−1; high, 120 kg N ha−1) under three tillage systems (NT, no-tillage; MT, minimum tillage; CT, conventional tillage). Tillage operations led to a pulse of soil CO2 flux. This pulse was linearly related to soil CO2 flux on the day before tillage operations under MT (slope = 4.22) and CT (slope = 16.7), indicating the extent of soil disturbances. However, the associated soil CO2-C losses during tillage operations were reduced and similar among different tillage systems. The soil CO2 flux after rainfall was higher under NT, where it was linearly related to soil temperatures (0.15 × soil temperature–1.06). Soil CO2 fluxes decreased on the following days as the soil dried. N fertilization affected CO2 flux in 5 out of 35 observation days, with higher fluxes with N fertilization under conservation tillage systems. Emissions after rainfall events led to large soil CO2-C losses, and these were of higher magnitude under conservation tillage systems (NT and MT)., This work was supported with by the Comision Interministerial de Ciencia y Tecnologia of Spain (Grants AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR). We also acknowledge the Ministry of Science and Innovation for funding the doctorate studies of F.J. Morell.

30 Pags., 6 Tabls., 3 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1475-2743

In Mediterranean semiarid areas, barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) are major crops because they are well adapted to limited-water environments. In this study we tested the performance of alternative rotations to the typical barley and wheat monocultures in a rainfed Mediterranean semiarid area of northeastern Spain under a no-tillage (NT) system. Four rotations were established and maintained over 6-yr period (1999-2000 to 2004-2005): a wheat monoculture (W-W-W), a barley monoculture (B-B-B), a wheat-barley-rapeseed (Brassica napus L.) rotation (W-B-R), and a wheat-barley-vetch (Vicia sativa L.) rotation (W-B-V). Aboveground biomass, grain yield, water use (WU), and water use effi ciency (WUE) were measured several times every season during the study period. All the parameters studied had a strong dependence on the rainfall variability found between growing seasons. Barley under rotation performed better than barley under monoculture in yield and WUE terms. However, wheat performed as well in a monoculture production system as it did in rotation. Rapeseed and vetch failed the 80 and 35% of the growing seasons, respectively. However, in semiarid Mediterranean agroecosystems of northeastern Spain, despite the benefi cial rotation eff ect of theses alternative crops on barley performance, economical benefi t of the overall rotation is doubtful since vetch failed in 2 out of 6 yr and rapeseed failed 5 out of 6 yr., This research was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR)

38 Pags.- 3 Figs. The definitive version is available at: http://link.springer.com/journal/13593, Dryland areas cover about 41 % of the Earth’s surface and sustain over 2 billion inhabitants. Soil carbon (C) in dryland areas is of crucial importance to maintain soil quality and productivity and a range of ecosystem services. Soil mismanagement has led to a significant loss of carbon in these areas, which in many of them entailed several land degradation processes such as soil erosion, reduction in crop productivity, lower soil water holding capacity, a decline in soil biodiversity, and, ultimately, desertification, hunger and poverty in developing countries. As a consequence, in dryland areas proper management practices and land use policies need to be implemented to increase the amount of C sequestered in the soil. When properly managed, dryland soils have a great potential to sequester carbon if financial incentives for implementation are provided. Dryland soils contain the largest pool of inorganic C. However, contrasting results are found in the literature on the magnitude of inorganic C sequestration under different management regimes. The rise of atmospheric carbon dioxide (CO2) levels will greatly affect dryland soils, since the positive effect of CO2 on crop productivity will be offset by a decrease of precipitation, thus increasing the susceptibility to soil erosion and crop failure. In dryland agriculture, any removal of crop residues implies a loss of soil organic carbon (SOC). Therefore, the adoption of no-tillage practices in field crops and growing cover crops in tree crops have a great potential in dryland areas due to the associated benefits of maintaining the soil surface covered by crop residues. Up to 80 % reduction in soil erosion has been reported when using no-tillage compared with conventional tillage. However, no-tillage must be maintained over the long term to enhance soil macroporosity and offset the emission of nitrous oxide (N2O) associated to the greater amount of water stored in the soil when no-tillage is used. Furthermore, the use of long fallow periods appears to be an inefficient practice for water conservation, since only 10–35 % of the rainfall received is available for the next crop when fallow is included in the rotation. Nevertheless, conservation agriculture practices are unlikely to be adopted in some developing countries where the need of crop residues for soil protection competes with other uses. Crop rotations, cover crops, crop residue retention, and conservation agriculture have a direct positive impact on biodiversity and other ecosystem services such as weed seed predation, abundance and distribution of a broad range of soil organisms, and bird nesting density and success. The objective of sequestering a significant amount of C in dryland soils is attainable and will result in social and environmental benefits., This work has been partially supported by the Spanish Ministry of Economy and Competitiveness (grants AGL 2013-49062-C4-1-R and AGL 2013-49062-C4-4-R).

20 Pags.- 9 Tabls.- 5 Figs.- Supp. data in Appendix A (online)., In crop insurance, the accuracy with which the insurer quantifies the actual risk is highly dependent on the availability on actual yield data. Crop models might be valuable tools to generate data on expected yields for risk assessment when no historical records are available. However, selecting a crop model for a specific objective, location and implementation scale is a difficult task. A look inside the different crop and soil modules to understand how outputs are obtained might facilitate model choice. The objectives of this paper were (i) to assess the usefulness of crop models to be used within a crop insurance analysis and design and (ii) to select the most suitable crop model for drought risk assessment in semi-arid regions in Spain. For that purpose first, a pre-selection of crop models simulating wheat yield under rainfed growing conditions at the field scale was made, and second, four selected models (Aquacrop, CERES-Wheat, CropSyst and WOFOST) were compared in terms of modelling approaches, process descriptions and model outputs. Outputs of the four models for the simulation of winter wheat growth are comparable when water is not limiting, but differences are larger when simulating yields under rainfed conditions. These differences in rainfed yields are mainly related to the dissimilar simulated soil water availability and the assumed linkages with dry matter formation. We concluded that for the simulation of winter wheat growth at field scale in such semi-arid conditions, CERES-Wheat and CropSyst are preferred. WOFOST is a satisfactory compromise between data availability and complexity when detail data on soil is limited. Aquacrop integrates physiological processes in some representative parameters, thus diminishing the number of input parameters, what is seen as an advantage when observed data is scarce. However, the high sensitivity of this model to low water availability limits its use in the region considered. Contrary to the use of ensembles of crop models, we endorse that efforts be concentrated on selecting or rebuilding a model that includes approaches that better describe the agronomic conditions of the regions in which they will be applied. The use of such complex methodologies as crop models is associated with numerous sources of uncertainty, although these models are the best tools available to get insight in these complex agronomic systems., This research was funded by the project MULCLIVAR, from the Spanish Ministerio de Economía y Competitividad (MINECO) CGL2012-38923-C02-02, A. Castaneda-Vera ˜ has a PhD grant from UPM.

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).

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.

This is an open-access article distributed under the terms of the Creative Commons Attribution License.-- et al., European agriculture is undergoing widespread changes that are likely to have profound impacts on farmland biodiversity. The development of tools that allow an assessment of the potential biodiversity effects of different land-use alternatives before changes occur is fundamental to guiding management decisions. In this study, we develop a resource-based model framework to estimate habitat suitability for target species, according to simple information on species' key resource requirements (diet, foraging habitat and nesting site), and examine whether it can be used to link land-use and local species' distribution. We take as a study case four steppe bird species in a lowland area of the north-eastern Iberian Peninsula. We also compare the performance of our resource-based approach to that obtained through habitat-based models relating species' occurrence and land-cover variables. Further, we use our resource-based approach to predict the effects that change in farming systems can have on farmland bird habitat suitability and compare these predictions with those obtained using the habitat-based models. Habitat suitability estimates generated by our resource-based models performed similarly (and better for one study species) than habitat based-models when predicting current species distribution. Moderate prediction success was achieved for three out of four species considered by resource-based models and for two of four by habitat-based models. Although, there is potential for improving the performance of resource-based models, they provide a structure for using available knowledge of the functional links between agricultural practices, provision of key resources and the response of organisms to predict potential effects of changing land-uses in a variety of context or the impacts of changes such as altered management practices that are not easily incorporated into habitat-based models., This study was supported by the Project ‘‘Steppeahead’’ funded by Fundación General del Consejo Superior de Investigaciones Científicas from Spain (FGCSIC) and Banco Santander. F.C. was supported by a JAE-Doc contract financed by CSIC and the European Social Fund (ESF). L.C. was supported by a postdoctoral contract funded by FGCSIC and Banco Santander. FARMDINDIS project, funded by Infraestructures.cat (Generalitat de Catalunya) and Aigües del Segarra-Garrigues SA, provided data on field censuses.

20 Pags.- 7 Figs.- 5 Tabls. The definitive version is available at: http://link.springer.com/journal/11104, Background and aims The effects of tillage and N fertilization on CO2 and CH4 emissions are a cause for concern worldwide. This paper quantifies these effects in a Mediterranean dryland area. Methods CO2 and CH4 fluxes were measured in two field experiments. A long-term experiment compared two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three N fertilization rates (0, 60 and 120 kg N ha−1). A short-term experiment compared NT and CT, three N fertilization doses (0, 75 and 150 kg N ha−1) and two types of fertilizer (mineral N and organic N with pig slurry). Aboveground and root biomass C inputs, soil organic carbon stocks and grain yield were also quantified. Results The NT treatment showed a greater mean CO2 flux than the CT treatment in both experiments. In the long-term experiment CH4 oxidation was greater under NT, whereas in the short-term experiment it was greater under CT. The fertilization treatments also affected CO2 emissions in the short-term experiment, with the greatest fluxes when 75 and 150 kg organic N ha−1 was applied. Overall, the amount of CO2 emitted ranged between 0.47 and 6.0 kg CO2−equivalent kg grain−1. NT lowered yield-scaled emissions in both experiments, but these treatment effects were largely driven by an increase in grain yield. Conclusions In dryland Mediterranean agroecosystems the combination of NT and medium rates of either mineral or organic N fertilization can be an appropriate strategy for optimizing CO2 and CH4 emissions and grain yield., 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), the Aragon Government and La Caixa (grant GA-LC-050/2011), the Department of Agriculture of the Government of Catalonia (grant 2012 AGEC 00012) and the European Union (FEDER funds).

An experiment was conducted on two soils in a semiarid area in the Spain’s Ebro valley. Soil A was a Fluventic Xerochrept of 120 cm depth and Soil B was a Lithic Xeric Torriorthent of 30 cm depth. Three tillage systems were compared in Soil A: subsoiler tillage, minimum tillage and no-tillage, and two (minimum tillage and no-tillage) in Soil B. The experiment was repeated for 5 years on Soil A and 3 years on Soil B. Root length density, volumetric water content and dry matter were measured at important developmental stages. Yield was determined at harvest. In Soil A, root length density and volumetric water content were significantly greater for no-tillage than for subsoiler or minimum tillage (up to 1.4 cm cm−3 and 5%, respectively), mainly in the upper part of the soil profile. At lower depths, differences as great as 0.8 cm cm−3 and 6% were also found. Mean yield (4 years) was similar between no-tillage (3608 kg ha−1) and minimum tillage (3508 kg ha−1), and significantly smaller for subsoiler tillage (3371 kg ha−1). In Soil B, no differences were observed between tillage systems for volumetric water content. Significant interactions between tillage and year were found for root length density, dry matter and yield. Mean yield (3 years) was not significantly different for minimum tillage (1806 kg ha−1) and no-tillage (1867 kg ha−1). The results in Soil A showed that surface conditions are of major importance in the water content of the soil and determined the differences among tillage systems. No-tillage favoured greater and deeper water accumulation in the soil profile and greater root growth. This makes this system potentially better for years of low rainfall. In Soil B no tillage system proved to be better because of the low water-holding capacity of this soil (56 mm).

27 páginas, 6 tablas, 1 figura.-- El pdf es el borrador del artículo., Tillage and N fertilization practices contribute to the balance between soil C inputs and outputs. Thus, the impacts of both practices and their interactions on soil organic C (SOC) dynamics must be studied. The main objective of this study was to determine long-term effects of tillage and N fertilization on soil biochemical properties in a long-term experiment established in 1996 on a dryland Typic Xerofluvent soil cropped with barley (Hordeum vulgare L.) in NE Spain. The response of SOC concentration, soil microbial biomass carbon (SMBC) and soil enzyme activities (DHA, dehydrogenase, and PRA, protease) to different tillage (no-tillage, NT; reduced tillage, RT; and conventional tillage, CT) and N treatments (zero, 0 kg N ha−1; medium, 60 kg N ha−1; and high, 120 kg N ha−1) were measured in 2008 at four soil depths (i.e., 0–5, 5–10, 10–25 and 25–50 cm). All the soil biochemical properties studied showed significant differences for tillage, depth and the interaction between tillage and soil depth. However, N fertilization rates only affected the SMBC content, which was greater under 120 kg N ha−1 than under 0 kg N ha−1 in the 10–25 cm soil layer. In the soil surface layer (0–5 cm), SOC, SMBC and DHA levels in CT were about 50% of the levels in the NT plots. However, in the 10–25 cm soil layer, a greater SOC concentration in CT compared with NT and RT was also accompanied by SMBC and DHA values 30% higher in CT. Below 25 cm soil depth, similar values of soil biochemical properties were found among tillage systems. There was a significant correlation among almost all the parameters studied, with the greatest correlations between SOC and SMBC and between SOC and DHA. In semiarid Mediterranean conditions, after 12 years of experiment, tillage impacted soil biochemical properties in a greater extent compared with N fertilization even though this effect was only limited to the upper soil layers., This work was supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (grants AGL2007-66320-CO2-01 and AGL2010-22050-CO3-01/02) and the European Union (FEDER funds).

9 Pags., 4 Tabls., 3 Figs., Agricultural management practices play an important role in soil organic carbon (SOC) protection within soil aggregates. However, there is a lack of information on the effects of N fertilization on C protection within aggregates under no-tillage (NT) systems. The effects of organic fertilization (with pig [Sus scrofa] slurry and poultry manure) and mineral N fertilization on soil aggregation and physical C protection dynamics under NT soils were investigated. Two experiments were established in a semiarid area of northeastern Spain. In the organic fertilization experiment, treatment with pig slurry at two N rates (100 and 200 kg N ha−1), poultry manure (100 kg N ha−1), and a control (0 kg N ha−1) treatment were compared. In the mineral fertilization experiment, increasing rates of N fertilizer (0, 40, 80, 120, and 160 kg N ha−1) were compared. Water-stable macroaggregates (>0.250 mm) and their C concentration, the distribution of dry-sieved aggregates, total SOC and microbial biomass carbon (MBC) were quantified in the soil surface in two cropping seasons. Organic fertilizers slightly increased the proportion of water-stable macroaggregates but caused no differences in MBC, SOC, or water-stable macroaggregate C concentration. In the mineral N fertilization experiment, similar water-stable macroaggregate, water-stable macroaggregate C and SOC concentrations were observed among N fertilizer doses. Overall differences in water-stable macroaggregates between sampling dates were greater than differences between fertilization treatments. Our study demonstrates that, in the short-term, the use of organic or mineral N fertilizers hardly improves the stability of the macroaggregates and their C protective capacity when NT is performed. This finding could be related to the limitations imposed by water in the Mediterranean areas and the buffering effect of long-term NT adoption on soil aggregate stability and C protection., D. Plaza-Bonilla was awarded an FPU fellowship by the Spanish Ministry of Education. This research was supported by the Comision Interministerial de Ciencia y Tecnología of Spain (AGL 2007-66320-C02-01 and AGL 2010-22050-C03-01).

13 Pags., 6 Figs., 4 Tabls., Aims Root respiration is a major contributor to soil CO2 flux, and its response to management practices needs to be evaluated. The aim was to determine the effect of management practices (tillage systems and nitrogen fertilization levels) on root respiration and to develop a model able to simulate root respiration and its components. Methods The study was carried out during two contrasting growing seasons (2007–2008 and 2008–2009). Root respiration, including root tissue respiration (R ts ) and rhizomicrobial respiration of exudates (R rz ), was estimated as the difference between the soil CO2 flux of cropped and bare soil (the so-called root exclusion technique). Additionally a novel sub-model of R ts , was used to simulate root respiration based on root growth and specific root respiration rates. Results Root respiration was reduced under no-tillage. The model agreed well with the patterns and the amounts of the observed values of root respiration, although prior calibration was needed. Conclusions Root respiration was reduced by the long-term adoption of no-tillage, but was increased by N fertilizer. The root exclusion technique and the model were useful means to estimate root respiration on cropland under semiarid Mediterranean conditions. Additionally the model successfully separated out the theoretical contributions of R ts and R rz to root respiration., This work was supported with by the Comision Interministerial de Ciencia y Tecnologia of Spain (Grants AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR). F.J. Morell received a grant for his doctorate studies from the Spanish Ministry of Science and Innovation, and wishes to acknowledge the Soil Science Department at Rothamsted Research for hosting during a research period in autumn 2009. Rothamsted Research is an institute of the UK Biotechnology and Biological Sciences Research Council. A.P. Whitmore acknowledges the support of the Institute Strategic Programme grant on Sustainable Soil Function.

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.

40 Pags., 6 Tabls., 7 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2389, Currently, there is little information about soil organic carbon (SOC) stocks and changes in Mediterranean areas at a regional scale. We modelled an area of 95 269 km2 in northeast Spain using the Global Environmental Facility Soil Organic Carbon (GEFSOC) system to predict SOC stocks and changes in pasture, forest and agricultural soils. The spatial distribution of the different land-use categories and their change over time was obtained by using the Corine database and official Spanish statistics on land use from 1926 to 2007. The model predicted the largest current SOC stock in forest soils at 578 Tg C. Agricultural soils were the second largest SOC reservoir, containing 244 Tg C. During the last 30 years, the model predicted a total SOC gain in the 0–30-cm soil layer of 34 Tg C. Forest and grassland-pasture soils had a decline in their stored SOC of 5 and 3 Tg C, respectively, because of the reduction in the soil surface occupied by both classes. The greatest SOC gain was predicted in agricultural soils with 42 Tg C caused by changes in management, which led to increases in C inputs. Although model uncertainty was not quantified, some hypothetical assumptions about the initialization and parameterization of the model could be potential sources of uncertainty. Our simulations predicted that in northeast Spain soil management has contributed to the sequestration of substantial amounts of atmospheric CO2 during the last 30 years. More research is needed in order to study the potential role of soils as atmospheric CO2 sinks under different managements and climatic conditions., Jorge Álvaro-Fuentes was awarded 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.

6 Pag., 2 Tabl, 6 Fig., Conservation tillage systems are being widely adopted in the Mediterranean region. A long-term field experiment was established in 1996 comparing three N fertilization levels (zero, 0 kg ha−1; medium, 60 kg ha−1; and high, 120 kg ha−1), under three tillage systems (conventional tillage, CT; minimum tillage, MT; and no-tillage, NT) in a semiarid Mediterranean agroecosystem annually cropped with winter barley (Hordeum vulgare, L., cultivar Hispanic), to study the response of root growth. During four consecutive growing seasons, from 2005 to 2009, root length density (RLD) and soil water content were evaluated. Penetration resistance (PR) and soil bulk density were only evaluated in the fourth and last year of this experiment. In dry years, root growth was similar under NT and MT systems but highly reduced under CT due to reduced water availability, which, in the surface 25 cm of soil was 7% and 18% lower than under MT and NT systems, respectively. However, in a wet year (i.e., 2009), RLD was double under CT than under NT due to reduced soil strength. PR at 5 to 15 cm soil depth under NT was 1MPa greater than under MT or CT. Root growth was not affected by N fertilization, in contrast to the response of grain yield that showed a significant interaction between N fertilization and tillage system. In spite of moderate soil compaction, which may reduce root growth in wet years, long-term NT adoption does not reduce grain yields for monoculture of barley under semiarid Mediterranean conditions., This work was supported with by the Comision Interministerial de Ciencia y Tecnologia of Spain (Grants AGL 2004-07763-C02-02 and AGL2007-66320-CO2-02/AGR). The doctoral studies of F.J. Morell were funded by the Spanish Ministry of Science and Innovation.

19 Pag., 2 Tabl., 2 Fot. The definitive version is available at: http://www.springerlink.com/, Intensive agriculture with deep tillage and soil inversion causes rapid soil deterioration with loss of soil organic matter content. This practice leads to a decrease of soil biological activity, a damage of the physical properties and a reduction of crop yields. Conservation agriculture aims to achieve sustainable and profitable agriculture through the application of three basic principles: minimal soil disturbance by conservation tillage, permanent soil cover and crop rotations. Any practice of conservation agriculture must maintain on the soil enough surface residues throughout the year. Conservation tillage is thus any tillage and planting system that maintains at least 30% of the soil surface covered by residues after planting to reduce soil erosion by water. Here we review the main advances about the adoption of conservation agriculture under Mediterranean conditions in Spain. There are major cost savings, e.g. fuel and fertilizer costs, compared with conventional agriculture. Conservation tillage has been proven to be highly efficient for water storage, to increase moderately the organic matter in the soil top layer, and to improve soil physical properties and aggregation. However, no tillage may induce greater soil compaction in some cases. In this case, an occasional tillage is advised. Furthermore, conservation tillage can reduce soil CO2 emissions, mobility and persistence of herbicides. In general, conservation tillage enhances biodiversity compared to conventional tillage. Crop yields under conservation tillage are similar or even greater than yields of traditional tillage. All these benefits show that ­conservation agriculture in Spain is a more sustainable alternative than conventional agriculture. Nonetheless, we have found from the literature analysis some constraints for its adoption, mainly due to inadequate extension and technology transfer systems and lack of access to specific inputs., This work was carried out with the support of the projects GOCE-CT-2004–505582–KASSA (EU), AGL2004–07763–CO2–01–AGR, AGL2007–66320–CO2–01–AGR and AGL2008–00424 from the Spanish CICYT, and the Research Group AGR 151 (Junta de Andalucía).

6 Pag., 3 Tabl., [EN] Spain is one of the countries with the highest greenhouse gas (GHG) emissions within the EU-27. Consequently, mitigation strategies need to be reported and quantified to accomplish the goals and requirements of the Kyoto Protocol. In this study, a first estimation of the carbon (C) mitigation potential of tillage reduction in Mediterranean rainfed Spain is presented. Results from eight studies carried out in Spain under rainfed agriculture to investigate the effects of no-tillage (NT) and reduced tillage (RT) compared with conventional tillage (CT) on soil organic carbon (SOC) were used. For current land surface under conservation tillage, NT and RT are sequestering 0.14 and 0.08 Tg C yr–1, respectively. Those rates represent 1.1% and 0.6% of the total CO2 emissions generated from agricultural activities in Spain during 2006. Alternatively, in a hypothetical scenario where all the arable dryland was under either NT or RT management, SOC sequestration would be 2.18 and 0.72 Tg C yr–1 representing 17.4% and 5.8% of the total 2006 CO2 equivalent emissions generated from the agricultural sector in Spain. This is a significant estimate that would help to achieve GHG emissions targets for the current commitment period of the Kyoto Protocol., [ES] Dentro de la Unión Europea, España es uno de los países con mayores emisiones de gases de efecto invernadero (GEI). Por tanto, es urgente establecer medidas de mitigación con el fin de alcanzar los objetivos del Protocolo de Kyoto. En este estudio se presenta una primera estimación del potencial de mitigación de carbono (C) a través de la reducción del laboreo en suelos de secano en zonas mediterráneas españolas. Se utilizaron los resultados de ocho estudios llevados a cabo en España en condiciones de secano sobre la influencia del no-laboreo (NL) y del laboreo reducido (LR) frente al laboreo convencional (LC), en el carbono orgánico del suelo (COS). Para la superficie actual bajo laboreo de conservación, NL y LR están secuestrando 0,14 y 0,08 Tg C año–1, respectivamente. Estas tasas representan el 1,1% y el 0,6%, respectivamente, del total de CO2 equivalente generado por la actividad agrícola en España durante 2006. Alternativamente, en un hipotético escenario en el que toda la superficie de secano disponible estuviera bajo NL o LR, el secuestro de COS sería 2,18 y 0,72 Tg C año–1, respectivamente, lo que representa el 17,4% y el 5,8% del total de CO2 equivalente generado por la actividad agrícola en España durante 2006. Estas estimaciones confirman la idoneidad de la reducción del laboreo para cumplir el objetivo de recortar las emisiones de GEI durante el periodo actual del Protocolo de Kyoto., The first author was awarded with a Beatriu de Pinós Postdoctoral Fellowship by the Comissionat per a Universitats i Recerca, Departament d’Innovació, Universitats i Empresa, of the Generalitat de Catalunya. This research was partly supported by the Comisión Interministerial de Ciencia y Tecnología of Spain (Grants GL2004-07763-CO2-01-AG and AGL2007- 66320-C02-C02-01/AGR).