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Intensive pig farming produces large amounts of slurry, which is applied to agricultural soils as fertilizer. A 7-year field study was performed to check the effect of pig slurry on soil properties and on the accumulation of some essential nutrients and heavy metals in a calcareous silty-loam soil (0-0.3 m) and in barley (Hordeum vulgare L.) plants in two cropping seasons with contrasting amounts of rainfall. Five fertilization treatments, control (no N applied), mineral fertilizer (90 kg N ha(-1)), and different N doses of pig slurry (146, 281, 534 kg N ha(-1)), were applied at sowing of a barley crop. Organic carbon, available P and K, and total P in soil increased with slurry dose. No differences were found in Co, Cr, Fe, Mn, Ni, and Pb soil concentrations. Slurries increased Cu, Mn, and Zn extractions and plant concentrations of P in straw and Zn in grain. However, the lowest slurry rate was able to maintain the highest grain yields while improving fertility. The results of this research study support the sustainability of pig slurry fertilization at appropriate rates in relation to soil chemical quality. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work was supported by the Spanish Ministry of Economy and Competitiveness and the Spanish National Institute for Agricultural Research and Experimentation (MINECO-INIA) through the project RTA2017-88-C3-3. The author A. Shakoor received a grant from the University of Lleida for his PhD studies (from 2019 to 2022 period).

En zonas de secano del Valle del Ebro (España), la siembra directa y el uso de deyecciones ganaderas resultan interesantes para reducir costes. Este trabajo tiene como objetivo evaluar, bajo siembra directa de cereal de invierno, el efecto de la fertilización con purines porcinos en la porosidad del horizonte superficial de un suelo de textura franco-limosa. Se establecieron seis dosis de purín, además de un control. El suelo se clasificó como Xerofluvent típico. La porosidad del suelo, sin alterar su estructura, se estudió mediante técnicas micromorfológicas. Los muestreos se realizaron en mayo. Se obtuvieron 21 muestras inalteradas de suelo (0-0,06 m de profundidad) que fueron tratadas hasta obtener láminas delgadas de 5 cm de alto, 13 cm de largo y 30 µm de grosor de las que se fotografiaron dos campos (3,15 cm × 4,2 cm). Los poros se estudiaron mediante análisis de imagen, clasificándose en diferentes intervalos de diámetros aparentes (DA), desde 15 µm hasta 400 µm. Se estableció una relación cuadrática significativa entre la cantidad de N aportada y el porcentaje de poros en los DA entre 200 µm y 400 µm (de 3,4 % a 5,2 % de porosidad total). A pesar de la detección de compactación y de la presencia de una estructura laminar, estos cambios en la porosidad responden a una mejora de la estructura, que podría deberse al hecho de facilitar la actividad de la macrofauna. Esta mejora estructural no se observa en aportaciones de purines inferiores a 100 kg N·ha–1 ni en las aportaciones más altas, próximas a 300 kg N·ha–1., Fil: Bosch-Serra, Ángela D. Universitat de Lleida. Departamento de Medio Ambiente y Ciencia del Suelo, Escuela Técnica Superior de Ingeniería Agraria; España, Fil: Mateo-Marín, Noemí. Universitat de Lleida. Departamento de Medio Ambiente y Ciencia del Suelo, Escuela Técnica Superior de Ingeniería Agraria; España, Fil: Molina, Gabriela. Universidad Católica de Córdoba. Facultad de Ciencias Agropecuarias; Argentina, Fil: Poch, Rosa M. Universitat de Lleida. Departamento de Medio Ambiente y Ciencia del Suelo, Escuela Técnica Superior de Ingeniería Agraria; España, Fil: Boixadera-Bosch, Monserrat M. niversitat de Lleida. Departamento de Medio Ambiente y Ciencia del Suelo, Escuela Técnica Superior de Ingeniería Agraria; España

The aim of this study was to evaluate the effects of sludge compost (SC) in two rates and pig slurry (PS) on soil quality, in the framework of a field experiment (19-year-old) in a Mediterranean rainfed system. The treatments were compared with mineral fertilization (MF) plus a control treatment (no N fertilization). Soil microstructure and types of voids, earthworm community and its bioturbation were studied using micromorphological methods. Two earthworm species, Koinodrilus roseus and Nicodrilus trapezoides were identified; the latter was not present in the SC treatments. Earthworm abundance and biomass were not affected by fertilization. Pig slurry increased bioturbation associated with earthworm activity, improved soil microstructure (crumb type) and increased the biopore presence (compound packing voids). The control and MF plots showed a platy to massive microstructure with an absence of faunal chambers. In SC plots, non-mixed soil-organic materials were observed and soil vughs were not visible. Composition differences between SC and PS and the total amount of OM applied may have had an impact on the activity and species of earthworms; such changes can be an early indicator of further potential impacts on soil quality however, further contaminant studies are needed to validate this initial assessment. This work was supported by the Spanish Ministry of Economy and Competitiveness and the Spanish National Institute for Agricultural Research and Experimentation (MINECO-INIA) through the projects RTA2013-57-C5-5 and RTA2017-88-C3-3.

Earthworms play an important role in the maintenance of soil ecosystem services. Their presence and activity are influenced by agricultural practices as fertilization. The objective of this research was to identify earthworm species and to quantify their abundance and biomass in a field experiment where different fertilization strategies were applied for a period of 12 years. The experiment was carried out under a semiarid Mediterranean climate, in a fallow year of a rainfed cereal system. Fertilization strategies were based on pig slurries from fattening pigs (PE) and from sows (PM) at different fresh doses distributed in six treatments: three treatments only included PE (one rate was 30 t ha−1yr−1applied at pre-sowing, and the other two treatments received 40 and 60 t ha−1yr−1applied at cereal tillering), two treatments only included PM (60 and 90 t ha−1yr−1applied at cereal tillering) and the last, it combined PE and PM (30 t ha−1yr−1of PE at pre-sowing plus 90 t ha−1 yr−1of PM at cereal tillering). Fertilization included a mineral fertilization treatment (0−FM) acting as a control.There were no variations in the abundance and biomass of earthworms registered according to the type of fertilization. Two earthworm species were identified. The endogeic species Koinodrilus roseuswas the most abundant (80%−100%). The anecic species Nicodrilus trapezoideswas notdetected in plots receiving the two highest doses of PE at cereal tillering. The absence of N. trapezoidescan be considered as a bioindicator of PE over-fertilization Las lombrices de tierra participan en el mantenimiento de los servicios ecosistémicos del suelo. Su presencia y actividad están influenciadas por las prácticas de manejo, entre ellas la fertilización. El objetivo de esta investigación fue cuantificar en un año bajo barbecho, la abundancia, biomasa y diversidad de especies de lombrices de tierra en respuesta a distintas estrategias de fertilización mantenidas durante 12 años en un agrosistema cerealístico de secano, bajo clima Mediterráneo semiárido. Esta fertilización se basó en purín de cerdo de engorde (PE) y de maternidad (PM), a distintas dosis de peso en fresco y distribuidas en seis tratamientos: tres tratamientos con PE (uno de 30 t ha−1 año−1 aplicado en pre-siembra y otros de 40 y 60 t ha−1 año−1 aplicados en cobertera), dos tratamientos con PM (60 y 90 t ha−1 año−1 aplicados en cobertera) y uno combinando PE y PM (30 t ha−1 año−1 de PE en pre-siembra más 90 t ha−1año−1 de PM en cobertera). Se incluyó un tratamiento con fertilización mineral (0−FM) que actuaba como control. No hubo variaciones en la abundancia y la biomasa de lombrices registradas según el tipo de fertilización. Se identificaron dos especies de lombrices. La especie endogeica Koinodrilus roseus predominó en cuanto a abundancia (80-100%). La especie anécica Nicodrilus trapezoides no se detectó en las parcelas que habían recibido en cobertera las dos dosis más elevadas de PE, por lo que la ausencia de esta especie puede considerarse como un bioindicador de situaciones de sobrefertilización con PE. Este estudio ha sido financiado con fondos del MINECO-INIA (Ministerio de Economía, Industria y Competitividad del Gobierno de España - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria) a través del proyecto RTA2017-88-C3-3. Alcira S. Valdez-Ibañez agradece a la Fundación Carolina la beca otorgada para la realización del doctorado. La Dra. María R. Yagüe-Carrasco agradece el ser beneficiaria de un contrato DOC-INIA-IMIDRA (BOE 25/07/2015). Se agradece al Dr. Antonio Pérez-Onteniente sus recomendaciones para la identificación de las especies, a Dyhia Boukirat de la Universidad Ibn-Khaldoun de Tiaret (Algeria) por su apoyo en el procesado de las muestras y a Silvia Porras y Silvana Nacci por su apoyo en los trabajos de campo.

Abatement of ammonia (NH3) emissions is crucial in calcareous soils under semiarid Mediterranean climates. The aim of the study was to compare NH3 emissions using different slurry application methods. An experiment was carried out on a clay loam soil to evaluate NH3 emissions before sowing (S-) and at winter cereal tillering (T-). Pig slurry was applied using two methods, one which applied slurry by splashing it over a plate (SP) and the other applied slurry in strips using trail hoses (TH). Emissions were measured using semi-static chambers at variable intervals for 12-13 d (315.5 h for S- and 287 h for T-). Maximum NH3 flux emissions were always observed during the earliest period of measurements after slurry spreading (3.5-5 h). Before sowing, regardless of the method, accumulated NH3 losses (during 315.5 h) ranged between 2-3 kg NH3-N ha-1 because of the low dry matter (DM) of the slurry content (

Animal excreta are commonly recycled as fertilizers, although attention should be given to environmental impacts. Legislation must also be adapted to new research findings. The framework of this study is an intensive fodder Mediterranean agricultural system affected by EU legislation on the protection of waters against nitrate pollution. This paper studies the effect of two N based dairy cattle slurry (DCS) rates (170 vs. 250 kg N ha-1 yr-1) plus additional mineral N (up to 450 kg N ha-1 divided between two crops), on different soil quality parameters. A control (no N applied) was included. The experiment, which lasted for 8 years, included forage maize followed by ryegrass, grain maize and rapeseed. In the whole period, the organic carbon inputs from the DCS treatments comprised C slurry inputs (14.8 or 21.9 Mg ha-1) plus the C input difference in crop residues (8.3 Mg ha-1) between DCS and the control treatment. In the 0-0.3 m soil depth, slurries significantly increased soil organic carbon (SOC) from by 2.3 or 2.7% yearly (c. 2.8 Mg C with 10 Mg C ha-1 input) mainly in its light fraction. The size of the microbial biomass increased by 5.1% yearly (c. 0.12 Mg C with 10 Mg C ha-1 input). A higher aggregate stability against slaking disruption was observed. Soil pH slightly decreased, P (Olsen) fertility increased (up to 10 mg P kg-1) as did K availability (up to 140 mg K kg-1) and Mn and Ni bioavailability. In rapeseed plants, seed Ca, S, Cu and Mn content increased as did K, S, Fe, Mn and Zn in the rest of the plant biomass. These changes were within acceptable concentration ranges. The higher N rate from DCS has proved useful for the circular nutrient economy, while improving soil physical and chemical quality and the sustainability of the agricultural system as a whole. This work was co-funded by Spanish Ministry of Economy and Competitiveness and the Spanish National Institute for Agricultural Research and Experimentation (MINECO-INIA) through the projects RTA2013-57-C5-5 and RTA2017-88-C3-3. It was also co-funded by the Government of Catalonia through the network of Plans for the improvement of the fertilization in agriculture, led by the Department of Agriculture, Livestock, Fisheries and Food. Alcira S. Valdez thanks Fundación Carolina for her PhD grant. PhD MR. Yagüe was beneficiary of an INIA contract (contract number INIA-DOC-CCAA2015) assigned to IMIDRA in Madrid.

Aim of study: Agricultural activities are the main source of volatilized ammonia (NH3). Maximum rates are reached within a few hours after slurry application. This study aimed to evaluate the influence of soil texture, tillage and slurry dry matter (DM) on NH3 volatilization.Area of study: Mediterranean semiarid environments (NE Spain).Material and methods: Ammonia volatilization from pig slurry directly applied on the soil surface was quantified in the laboratory, in soil samples from two experimental sites with different soil textures: silty loam and sandy loam. Field treatments consisted of two tillage management practices: till by disc-harrowing or no-till. At topdressing (cereal tillering), tillage treatments were combined with slurries of different DM contents applied onto the silty loam soil. Measurements were done for two cereal cropping seasons and during the period of maximum NH3 flux (12 h after slurry application). A photoacoustic analyzer was used.Main results: Slurry spreading at sowing resulted in low volatilization (0.7-9% of NH4+-N applied) as it also did at topdressing (0.3-1.4% of NH4+-N applied). At sowing, ammonia volatilization from high DM slurry (>7.5%) was significantly enhanced by no-till in both soils. At topdressing, this result was also found in records on silty loam soil. No differences were found between tillage systems when slurry of low DM content was applied, whatever the soil texture and application moment. Although NH3 volatilization was probably affected by the laboratory conditions, the comparisons between treatments were still valuable.Research highlights: Ammonia volatilization abatement can be improved (

Soil fertilisation affects greenhouse gas emissions. The objective of this study was to compare the effect of different fertilisation strategies on N2O, CH4 emissions and on ecosystem respiration (CO2 emissions), during different periods of rice cultivation (rice crop, postharvest period, and seedling) under Mediterranean climate. Emissions were quantified weekly by the photoacoustic technique at two sites. At Site 1 (2011 and 2012), background treatments were 2 doses of chicken manure (CM): 90 and 170 kg NH4+-N ha− 1 (CM-90, CM-170), urea (U, 150 kg N ha− 1) and no-N (control). Fifty kilogram N ha− 1 ammonium sulphate (AS) were topdress applied to all of them. At Site 2 (2012), background treatments were 2 doses of pig slurry (PS): 91 and 152 kg NH4+-N ha− 1 (PS-91, PS-152) and ammonium sulphate (AS) at 120 kg NH4+-N ha− 1 and no-N (control). Sixty kilogram NH4+-N ha− 1 as AS were topdress applied to AS and PS-91. During seedling, global warming potential (GWP) was ~ 3.5-17% of that of the whole rice crop for the CM treatments. The postharvest period was a net sink for CH4, and CO2 emissions only increased for the CM-170 treatment (up to 2 Mg CO2 ha− 1). The GWP of the entire rice crop reached 17 Mg CO2-eq ha− 1 for U, and was 14 for CM-170, and 37 for CM-90. The application of PS at agronomic doses (~ 170 kg N ha− 1) allowed high yields (~ 7.4 Mg ha− 1), the control of GWP (~ 6.5 Mg CO2-eq ha− 1), and a 13% reduction in greenhouse gas intensity (GHGI) to 0.89 kg CO2-eq kg− 1 when compared to AS (1.02 kg CO2-eq kg− 1). This study was supported by the National Institute for Agricultural and Food Scientific Research and Technology of Spain-INIA (projects RTA2010-126 and RTA2013-57 and predoctoral grant to Beatriz Moreno-García) and by the EFRD (European Fund for Regional Development). Stefania C. Maris would like to express her gratitude for the grant provided by the University of Lleida for her PhD studies. We are also grateful to S. Porras (UdL), E. Pla and N. Tomás (IRTA-Amposta), M. Izquierdo, J. Gaudó and J.M. Acín (CITA) for field assistance, and to Dr. D. Quílez (CITA) for her useful comments.

The efficient use by crops of nitrogen from manures is an agronomic and environmental issue, mainly in double-annual forage cropping systems linked to livestock production.A six-year trial was conducted for a biennial rotation of four forage crops: oat-sorghum (first year) and ryegrass-maize (second year) in a humid Mediter ranean area. Ten fertilization treatments were introduced: a control (without N);two minerals equivalent to 250 kg N ha-1yr-1 applied at sowing or as sidedressing; dairy cattle manure at a rate of 170, 250 and 500 kg N ha-1yr-1 and four treatments where the two lowest manure rates were supplemented with 80 or 160 kg mineral N ha -1 yr -1.They were distributed according to a randomized block design with three blocks. The highest N mineral soil content was found in the summer of the third rotation, in plots where no manure was applied. The yearly incorporation of manure reduced, in successive cropping seasons, the amount of additional mineral N n eeded as sidedressing to achieve the highest yields.Besides, in the last two years, there was no need for mineral N application for the manure rate of 250 kg N ha -1yr-1. This amount always covered the oat-sorghum N uptake. In the ryegrass-maize sequence uptakes were as high as 3 kg N ha-1yr-1.In the medium term, the intermediate manure rate (250 kg N ha -1 yr -1) optimizes nutrient recycling within the farming system, and it should be considered in the analysis ofthresholds for N of organic orig in to be applied to systems with high N demand.

In the European Union, the maintenance of soil quality is a key point in agricultural policy. The effect of additions of dairy cattle (Bos taurus) manure (DCM) during a period of 11 years were evaluated in a soil under irrigated maize (Zea mays L.) monoculture. DCM was applied at sowing, at wet-weight rates of 30 or 60 Mg ha−1yr−1 (30DCM or 60DCM). These were compared with a mineral-N treatment (300 kg N ha−1, MNF), applied at 6–8 emerged leaves and with a control (no N, no manure). Treatments were distributed in a randomized block design. Factors analysed were stability against wetting stress disaggregation, porosity, soil organic carbon (SOC) fractions and earthworm abundance, studied eight months after the last manure application. The application rate of 30DCM increased aggregate stability and the light SOC fraction, but not the pore volume, nor the earthworm abundance, compared with MNF. The DCM rates did not result in unbalanced agronomic advantages versus MNF, as high yields (17–18 Mg ha−1 yr−1) were obtained. In Mediterranean environments, the use of DCM should be encouraged mainly because of its contribution to the light SOC fraction which protects dry macro-aggregates from implosion (slaking) during the wetting process. Thus, in intensive agricultural systems, it protects soil from physical degradation. The authors thank Elena González, Irma Geli and Albert Roselló for field assistance and Montse Antúnez and Nouha Gobber for laboratory assistance. This study was supported by the National Institute for Agricultural and Food Scientific Research and Technology of Spain-INIA (project RTA2013-057-C05-05) funds. The initial field maintenance was done through different Spanish projects from the National Institute for Agricultural and Food Scientific Research and Technology (INIA) and from the Interministerial Science and Technology Research commission (CICYT): AGL2001-2214-C06; RTA2003-066-C4, AGL2005-08020-C05-03.The subsequent field maintenance by IRTA-Mas Badia and the Department of Agriculture, Livestock, Fisheries, Food and Natural Environment from Generalitat de Catalunya, is fully acknowledged. This research article received a grant for linguistic revision from the Language Institute of the University of Lleida (2015 call).

Organic fertilizers (manures and slurries) applied repeatedly over many cropping seasons favourably influence nutrient recycling, maintenance of soil organic matter (SOM), and improve soil quality parameters such as soil aggregation and porosity. These aspects are particularly relevant in Mediterranean environments characterized by low SOM. This study was set up in a subhumid Mediterranean area where two different trials, devoted to winter cereals, were fertilized with dairy cattle manure (DCM) or pig slurry (PS) for a period of 12 years. One objective of this research was to evaluate the impacts of these fertilization practices on aggregate stability and SOM fractions, when compared with a mineral N fertilizer and a control (no-N) treatment. Porosity and pore shape were also studied in PS plots. The use of DCM significantly increased water stable aggregates by up to 16.4–18.0 %. Slurry addition did not affect aggregation but it increased the area occupied by pores >65 µm. Soil organic carbon (SOC) and light organic fraction (0.05–0.2 mm) increased with DCM incorporation but in PS treatments the SOC increment was non-significant. Data from DCM and PS together showed a positive and significant linear relationship between SOC (p < 0.05, R2 = 0.60), SOC light fraction (p < 0.01, R2 = 0.75) and SOC light fraction at 0.05–0.2 mm size (p < 0.01, R2 = 0.83), with water-stable aggregate. The use of animal residues (DCM or PS), applied according to an N criterion, increased available phosphorus and potassium soil content while improving yields. The enrichment of soil nutrients with DCM and PS use requires further research in order to avoid potential environmental impacts. The authors thank IRTA Mas Badia staff, all along the period of the experiment for field assistance and Montse Antúnez and Belén Martı́ nez for laboratory assistance. The initial field maintenance was done through a project fromInterministerial Science and Technology Research commission (CICYT) of Spain (AGL2001-2214-C06). The subsequent fieldmaintenance and measurements development were supported through the Plans for the improvement of crop fertilization, led by the Department of Agriculture, Livestock, Fisheries, Food and Natural Environment from Generalitat de Catalonia and through different projects from the National Institute for Agricultural and Food Scientific Research and Technology of Spain (INIA): RTA04-114-C3; RTA2010-00126-C02-02 and RTA2013-57-C5-05.

A method of rehabilitating coal mine soils was studied under the conditions of a semi-arid climate, lack of topsoil but availability of farm by-products in NE Spain. The objectives of the research were to assess a new method in order to achieve a suitable substrate for the establishment of native vegetation, to evaluate environmental impacts associated with the reclamation process, and to determine the time necessary to integrate the treated area into the surrounding environment. Eight plots (10 × 35 m2) were established in September 1997. Substrate combinations of two types of mine spoil (coal dust and coarse-sized material), two levels of pig slurry (39 and 94 Mg ha−1dry-wt), and cereal straw (0 and 15 Mg ha−1) were applied. Monitoring of select physical and chemical soil properties and vegetation characteristics was performed from 1997 until 2005. The bulk density and the saturated hydraulic conductivity measured did not limit plant development and water availability. Initial substrate salinity (1.37 S...

Agro-hydrological models have increasingly become useful and powerful tools in optimizing water and fertilizer application, and in studying the environmental consequences. Accurate prediction of water dynamics in such models is essential for models to produce reasonable results. In this study, detailed simulations were performed for water dynamics of rainfed winter wheat and barley grown under a Mediterranean climate over a 10-year period. The model employed (Yang et al., 2009. J. Hydrol., 370, 177-190) uses easily available agronomic data, and takes into consideration of all key soil and plant processes in controlling water dynamics in the soil-crop system, including the dynamics of root growth. The water requirement for crop growth was calculated according to the FAO56, and the soil hydraulic properties were estimated using peto-transfer functions (PTFs) based on soil physical properties and soil organic matter content. Results show that the simulated values of soil water content at the depths of 15, 45 and 75 cm agreed with the measurements well with the root of the mean squared errors of 0.027 cm3 cm-3 and the model agreement index of 0.875. The simulated seasonal evapotranspiration (ET) ranged from 208 to 388 mm, and grain yield was found to correlate with the simulated seasonal ET in a linear manner within the studied ET range. The simulated rates of grain yield increase were 17.3 and 23.7 kg ha-l for every mm of water evapotranspired for wheat and barley, respectively. The good agreement of soil water content between measurement and simulation and the simulated relationships between grain yield and seasonal ET supported by the data in the literature indicates that the model performed well in modelling water dynamics for the studied soil-crop system, and therefore has the potential to be applied reliably and widely in precision agriculture. Finally, a two-staged approach using inverse modelling techniques to further improve model performance was discussed. This study was funded by National Institute for Agricultural and Food Scientific Research and Technology of Spain-INIA (projects RTA2004-114 and RTA2010-126), FEDER (European Fund for Regional Development), FEADER (European Agricultural Fund for Rural Development), the Departament d’Universitats, Recerca i Societat de la Informació. Generalitat de Catalunya (2010-PIV-DGR), and National Natural Science Foundation of China (Grant No. 51379187). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Fertilization with animal residues together with no-tillage is being widely used in dryland Mediterranean agriculture. The aim of this work is to assess the potential impacts of these combined anagement practices on oribatid mite species, and to evaluate their potential use as bioindicators of soil disturbances. From an experiment established ten years ago, eight fertilization treatments (including minerals or pig slurries), all combined with minimum tillage (MT) and no-tillage (NT), were studied. Four of these combinations were sampled three times during the winter cereal cropping season. The rest, and a eighbouring oak forest, were only sampled close to the end of the season (May). In total, 34 oribatid species and 4140 individuals were recovered. Oribatid abundance responded positively (p < 0.05) to the reduction of tillage intensity (NT) and marginally (p < 0.1) to slurry fertilization at sowing (close to maximum legislation allowed rate

38 Pags., 4 Figs., 5 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/15375110, Pig slurries (PS) are widely applied to soil as fertilisers. Compositional variability, as shown in this study, is the main constraint on their efficient use. Slurry samples, collected from 126 commercial pig farms were analysed and organic nitrogen (ON), ammoniacal nitrogen (AN), total nitrogen (TN), total potassium (TK), total phosphorus (TP) content, pH, EC (electrical conductivity), DM (dry matter) and OM (organic matter) quantified. Relationships between major nutrient contents of PS and its physical and chemical properties were analysed. AN and TK were linearly related to EC (p < 0.0001) for values lower than 5.6 kg [AN] m−3 and 5 kg [TK] m−3 with coefficients of determination (R2) of 0.86 and 0.58 respectively, in agreement with previous linear models. At higher AN values (which means EC > 40 dS m−1) linearity cannot be maintained, which has important consequences for direct slurry EC measurements. ON and TP in slurries were closely related (p < 0.0001) to DM with R2 of 0.90 and 0.68 respectively., This study was funded by the National Institute for Agricultural and Food Scientific Research and Technology of Spain (INIA), projects SC00-061, RTA04-114 and RTA10-126.

Applying pig slurry to the land as fertilizer at appropriate agronomic rates is important to close nutrient cycles and optimize the value of organic matter. However a long-term discussion has taken place about its effects on soil quality. In the north-east of Spain, eight fertilization strategies were evaluated on the soil quality parameters' aggregate stability, soil organic matter (SOM) physical fractions and soil microbial biomass (SMB). Six strategies used different pig slurries (PS) which provided organic matter from 1.7 to 2.6 t ha(-1)yr(-1), the rest (mineral N fertilization and a control) did not. Pig slurries were applied at sowing and/or at cereal tillering, as sidedressing. Field experiments were maintained for an 8-year period, in a silty loam soil devoted to a rainfed winter cereal. Soil samples were taken once, before the last sidedressing in 2011. Aggregate stability was quantified using the standard water-stable aggregate method but including a modification which meant that pre-wetting was avoided (WSA(MOD)). When using the WSA(MOD) method, we found a tendency for the percentage of water-stable aggregates to increase due to PS application (differences of up to 74% in the increment) and it was more marked the nearer they were measured to the application time (3 months vs. 12 months). The strategies which include PS show a positive effect on the SOM amount, mainly in the 0.05-0.2 mm light fraction, which increased by up to 34% with every 10 t ha(-1) organic C applied, and on SMB (up to 53% increment). There is a positive and significant linear relationship (p0.05, R(2) = 0.75) between the SOM light fraction (%) and the water-stable aggregates soil content (%, WSA(MOD)). Thus, the introduction of PS in fertilization strategies improves soil quality parameters. However, the soil quality benefits need to be balanced with any other potential environmental impact.

Using cattle manure (CM) fertilization, it is challenging to optimize nitrogen use. Our work aimed to assess nitrogen efficiencies, in a six-year experiment which involved three biennial rotations of four crops: oat-sorghum (first year) and ryegrass-maize (second year). This rotation was maintained in a rainfed humid Mediterranean area of Spain. Fertilization treatments included: control (no-N), 250 kg mineral N ha-1year-1 (250MN), three CM rates (170, 250 and 500 kg N ha-1year-1), and four treatments where the two lowest CM rates were complemented with either 80 or 160 kg mineral N ha-1 year-1. The treatments were distributed randomly in each of three blocks. Maximum dry-matter yield (~44-49 t ha-1 rotation-1) was achieved in the third rotation, and only the control and the 170CM yielded significantly less. Inside the limitations of the EU Nitrate Directive, the N steady state of 170CM always requires a mineral complement (80 kg N ha-1) to maximize N agronomic efficiency. The maximum nitrogen fertilizer replacement value (250CM vs. 250MN) was 0.67, without significant differences between the two treatments in other N related efficiency indexes, which indicates that plants took advantage of N residual effects. Nitrogen losses by leaching in the 250CM were around 5-7% of the N applied. This reinforces the sustainability of manure recycling in long cropping seasons. This research was financially supported by the following institutions involved in the improvement of fertilization practices in La Garrotxa, north-east Spain: Garrotxa Volcanic Zone Natural Park, Consortium SIGMA, IRTA-Mas Badia Foundation and Ministry of Agriculture, Livestock, Fisheries and Food (Generalitat de Catalunya, Catalonia, Spain).

The use of organic fertilizers from stock-raising activity is usually based on nitrogen (N) criterion. The objective of our research is to evaluate whether this N criterion lead to positive or environmentally risky changes, mainly in organic carbon (OC) storage and the availability of the main nutrients. Three biennial rotations of four crops were set up (in a 6-year time-frame). The treatments included a control (no N added), two mineral treatments where 250 kg N ha-1 yr-1 were provided at two different times during the rotation, three cattle manure treatments which provided 170, 250 and 500 kg N ha-1 yr-1 and four treatments in which the two lowest manure rates were complemented with mineral N (80 and 160 kg N ha-1 yr-1). Over the whole 6-year period, the measured soil OC increases were equivalent to ca. 25, 43 and 35% of the manure OC applied respectively, following the manure rate increases. Furthermore, equivalences were of -5, 23 and 25% when compared with full mineral fertilization. The positive slope of phosphorus availability was 1.2 mg Olsen-P kg-1 to 10 kg P ha-1 applied from manures (N:P=4) when starting from a threshold of 15.9 mg Olsen-P kg-1. The availability of other nutrients (Mg, Zn) and Na also increased with rates. In a medium-term experiment, the manure rate of 250 kg N ha-1 yr-1 optimized the nutrient recirculation. In the long-term, rotations should be redesigned to control P surpluses or the amount of N applied from manures should be reduced. This research was financially supported by several institutions involved in the improvement of fertilization practices in La Garrotxa (NE of Spain). These institutions are Garrotxa Volcanic Zone Natural Park, SIGMA Consortium, IRTA-Mas Badia and Department of Agriculture, Livestock, Fisheries and Food (Generalitat de Catalunya, Catalonia, Spain). This research article received a grant for linguistic revision from the Language Institute of the University of Lleida.

In the context of the circular economy, the use of animal excrements as fertilizers is encouraged, but the addition of such organic materials can develop soil water repellency (SWR) or hydrophobicity. There is a lack of consensus about how to assess SWR in agricultural soils. This work evaluated SWR when pig slurries were applied onto soil using the two most common testing methods: the water drop penetration time (WDPT) and the molarity of ethanol droplet (MED) tests. The experiment consisted of five different slurry treatments plus a control (no slurry added). At sowing, slurry from fattening pigs (SF) or no slurry application was combined with a second application at the cereal tillering stage, in which SF, slurry from sows (SS) or no-slurry were the treatments. Soil water repellency was tested at cereal tillering before slurry application and then during the following 47 days. At each sampling date, hydrophobicity was tested in undisturbed samples at field-moist and after 25 °C, 65 °C, and 105 °C oven drying. Disturbed samples were tested after 40 °C oven drying. Soil disturbance removed SWR. Under field conditions, undisturbed samples attained the maximum SWR expression 7d from pig slurry application; moderate and very severe scores using WDPT and MED were respectively attained. From 14d to the end of the experiment, the highest SWR was observed after 105 °C oven drying and when SF applications at sowing (900 kg TOC ha−1) had been combined with SS applications at cereal tillering (1894 kg TOC ha−1). Slurry hydrophobic compounds rather than slurry dry matter influenced SWR expression which is enhanced as the soil dries. The persistence of repellency (WDPT test) was more sensitive to detecting changes in SWR between treatments than the changes in its severity (MED test). The importance of the SWR described hereafter slurry application will depend on plant cover over the soil and the effects in slaking prevention in order to avoid superficial water runoff. Field assistance from J.C. Estruga, J.M. Llop, B. Martínez and N. Mateo and laboratory assistance from M. Antúnez and S. Porras (University of Lleida); D. Pezzolla, G. Gigliotti and “Laboratorio di Chimica Agraria – Chimica delle Biomasse di Uso Agrario” (University of Perugia) is fully acknowledged. Funding: This work was supported by the Spanish Ministry of Economy and Competitiveness and the Spanish National Institute for Agricultural Research and Experimentation (MINECO-INIA) through the projects RTA2013-57-C5-5 and RTA2017-88-C3-3. JADE-Plus scholarship from Bank of Santander-University of Lleida for D.E. Jiménez-De-Santiago PhD studies. Grant for linguistic revision from the Language Institute of the University of Lleida.

In dryland agricultural systems, pig slurry (PS) is usually applied to cereal crops only at sowing, and slurries accumulate for the rest of the year in pits. In this context, a four-year experiment was established in order to evaluate the feasibility of PS applications at the barley or wheat tillering stage. The main treatments were PS either applied at sowing (25 Mg ha-1) or not, but they alternated after a two-year period. Both were annually combined with eight side-dressing treatmen ts at cereal tillering: mineral N as NH4NO3(M; 60 or 120 kg N ha-1), PS from fattening pigs (PSf; 17, 30, 54 Mg ha-1yr-1),28PS from sows (PSs; 25, 45, 81 Mg ha-1yr-1) and a treatment without N. The combined fertilization treatments were 18 plus a control (no N applied). In the context of crop rotation, the biennial alternation of PS applied at sowing or not allowed the control of soil nitrate increments, while PS side-dressing improved N recovery ompared with a unique application at sowing. The highest yields (>3.6 Mg ha-1yr-1) were obtained with an annual average (4-year) N rate close to 173 kg N ha-1(±40kg N ha-1). The best overall strategies corresponded to PSs hide-dressings of 50-90 kg N ha-1. These PSs rates also recorded the highest values on the five calculated N-efficiency indexes, which were higher than or similar to results from M side-dressings or those recorded in the literature. These similarities (M vs. PSs) were also shown by the reduction of unaccounted-for N inside the overall N balance. Thus, split PS application during the crop cycle is a sound fertilization option in dryland systems.