BUSCADOR RECOLECTA

Impairments in leaf nitrogen (N) assimilation in C3 plants have been identified as processes conditioning photosynthesis under elevated [CO2], especially when N is supplied as nitrate. Leaf N status is usually improved under ammonium nutrition and elevated [CO2]. However, ammonium fertilization is usually accompanied by the appearance of oxidative stress symptoms, which constrains plant development. To understand how the limitations of direct fertilization with ammonium (growth reduction attributed to ammonium toxicity) can be overcome, the effects of elevated [CO2] (800 ppm) exposure were studied in the Arabidopsis thaliana double nitrate reductase defective mutant, nia1-1/chl3-5 (which preferentially assimilates ammonium as its nitrogen source). Analysis of the physiology, metabolites and gene expression was carried out in roots and shoot organs. Our study clearly showed that elevated [CO2] improved the inhibited phenotype of the nitrate reductase double mutant. Both the photosynthetic rates and the leaf N content of the NR mutant under elevated CO2 were similar to wild type plants. The growth of the nitrate reductase mutant was linked to its ability to overcome ammonium-associated photoinhibition processes at 800 ppm [CO2]. More specifically: (i) the capacity of NR mutants to equilibrate energy availability, as reflected by the electron transport equilibrium reached (photosynthesis, photorespiration and respiration), (ii) as well as by the upregulation of genes involved in stress tolerance were identified as the processes involved in the improved performance of NR mutants., This work has been funded by the Spanish National Research and Development Programme (AGL2009-13339-C02-02, AGL2011-30386-C02-02 and AGL2012-37815-C05-05). Ivan Jauregui was the holder of a FPI fellowship from the Spanish Ministry of Economy and Competitiveness.

The natural 15N/14N isotope composition (δ15N) of a tissue is a consequence of its N source and N physiological mechanisms in response to the environment. It could potentially be used as a tracer of N metabolism in plants under changing environmental conditions, where primary N metabolism may be complex, and losses and gains of N fluctuate over time. In order to test the utility of δ15N as an indicator of plant N status in N2-fixing plants grown under various environmental conditions, alfalfa (Medicago sativa L.) plants were subjected to distinct conditions of [CO2] (400 vs. 700 μmol mol−1), temperature (ambient vs. ambient +4°C) and water availability (fully watered vs. water deficiency—WD). As expected, increased [CO2] and temperature stimulated photosynthetic rates and plant growth, whereas these parameters were negatively affected by WD. The determination of δ15N in leaves, stems, roots, and nodules showed that leaves were the most representative organs of the plant response to increased [CO2] and WD. Depletion of heavier N isotopes in plants grown under higher [CO2] and WD conditions reflected decreased transpiration rates, but could also be related to a higher N demand in leaves, as suggested by the decreased leaf N and total soluble protein (TSP) contents detected at 700 μmol mol−1 [CO2] and WD conditions. In summary, leaf δ15N provides relevant information integrating parameters which condition plant responsiveness (e.g., photosynthesis, TSP, N demand, and water transpiration) to environmental conditions., This work was supported by the Spanish Economy and Competiveness ministry (AGL-2012-37815-CO5-05, AGL2011-30386-C02-02 and Ramón y Cajal research grant) and by the Portuguese FCT (PTDC/BIA-ECS/122214/2010). IA was supported by a postdoctoral Fellowship from the Government of Navarra (Anabasid outgoing Programme) and by a postdoctoral Fellowship from the Portuguese FCT (SFRH/BPD/90436/2012).

The amount of carbon dioxide (CO2) in Earth's atmosphere has exceeded 400 parts per million
(ppm) during three continuous months of observations in 2014, which is an absolute record for
the last 800,000 years. As a consequence, plants, as photosynthetic organisms, will inevitably be
influenced by the changed growing conditions that result from the increased [CO2]. The effect
of increased [CO2] on plants has been widely studied and goes far beyond favouring
carboxylation of Rubisco and generating higher growth rates. The present thesis aims to
highlight the relevance of different nitrogen sources in the response of Arabidopsis thaliana, a C3
model plant, to elevated [CO2]. For this purpose, this has been an integrated study of leaf and
root organs combining techniques that range from plant physiology to molecular biology. Under
nitrate nutrition and elevated [CO2] conditions, Arabidopsis thaliana plants increase their biomass
and maximum photosynthetic rates; nevertheless, the total soluble protein, Rubisco content and
leaf N content reveal a general decrease in leaf N availability (chapter I). Although the expression
of nitrate transporters was substantially upregulated in roots, plants did not efficiently transport
nitrate and other minerals from roots to leaves, which compromised leaf N and mineral status.
Therefore, our results suggest that the diminution of transpiration rates causes a reduction in the
xylem flux, which inexorably generates an imbalance in the transport of nitrate and mineral
elements between organs under elevated [CO2]. Moreover, root nitrate assimilation (based on
the amino acid content) is favoured in order to overcome N limitations due to the reduction in
leaf nitrate assimilation. In chapter II plant performance under elevated [CO2] and ammonium
nitrate conditions was characterized and it was found that biomass doubled due to substantially
increased photosynthetic rates. Gas exchange characterization revealed that these plants
overcame photosynthetic acclimation. Plants maintained Rubisco concentrations at control
levels alongside enhanced energy efficiency. The increments found in leaf carbohydrates and
organic acid content linked to enhanced respiration rates supported the fact that the plants under
elevated [CO2] maintained their energy status. The transcriptomic analysis enabled the
identification of photoassimilate allocation and remobilization as fundamental processes used by the plants to avoid photosynthetic acclimatization. Moreover, based on the relationship between
plant carbon status and hormone functioning, the transcriptomic analyses provided an
explanation of why phenology accelerates under elevated [CO2]. Finally, in chapter III the
relevance of ammonium nutrition under elevated [CO2] was analysed; for this purpose a double
nitrate reductase mutant (NR mutant, nia1-1/chl3-5 defective) was used. These results highlight
that plants under elevated [CO2] which preferentially assimilate ammonium as their only N
source maintain leaf growth and photosynthetic rates similar to plants receiving ammonium
nitrate. However, under ambient [CO2] concentrations, ammonium toxicity symptoms emerge
and development is extremely constrained. In elevated [CO2] conditions, an NR mutant
maintained the energy supply for the Calvin cycle pathway and managed efficient
photoassimilate transport between plant tissues. Furthermore, the data suggest active ammonium
assimilation in leaves due to the exceptional conditions (C skeletons, ATP, adequate pH
homeostasis and no photoinhibition) of these plants under elevated [CO2]. Hence, the results
obtained in the present doctoral thesis aim towards the incorporation of the source of nitrogen as
key in the response at the elevated [CO2] of Arabidopsis thaliana plants. Consequently, the
present doctoral thesis aims to determine whether the incorporation of the correct source of
nitrogen is the key component in how Arabidopsis thaliana plants respond to elevated [CO2]., This work was funded by the project: AGL2009-13339-C02-02 and AGL2012-37815-C05-5, Programa Oficial de Doctorado en Agrobiología Ambiental (RD 1393/2007), Ingurumen Agrobiologiako Doktoretza Programa Ofiziala (ED 1393/2007)

Home composting is a powerful tool, which is spreading in different parts of the world, to reduce the generation of municipal waste. However, there is debate concerning the appropriateness, in terms of domestic hygiene and safety, of keeping a composter bin in the household deputed to kitchen waste of animal origin, such as meat or fish scraps and pet droppings. The purpose of our work was to study how the addition of meat scraps to household waste influences the composting process and the quality of the final compost obtained. We compared four raw material mixtures, characterized by a different combination of vegetable and meat waste and different ratios of woody bulking agent. Changes in temperature, mass and volume, phenotypic microbial diversity (by Biolog TM) and organic matter humification were determined during the process. At the end of the experiment, the four composts were weighed and characterized by physicochemical analysis. In addition, the presence of viable weed seeds was investigated and a germination bioassay was carried out to determine the level of phytotoxicity. Finally, the levels of pathogens (E. coli and Salmonella spp.) were also determined in the final compost.
Here we show that the presence of meat waste as raw feedstock for composting in bins can improve the activity of the process, the physicochemical characteristics and maturity of the compost obtained, without significantly affecting its salinity, pH and phytotoxicity. Pathogen levels were low, showing that they can be controlled by an intensive management and proper handling of the composter bins., The experiments were financially supported by the Spanish
Ministry of Science and Technology (Project AGL2012-37815-
C05-05).

Comunicación presentada a las XI Jornadas de Sustratos de la SECH, celebradas en Zizurkil (Gipuzkoa) el 25-27 de junio de 2014., La utilización de compost de FORM como fertilizante es una práctica inocua y
segura ampliamente implantada en la unión europea y que presenta gran cantidad de
ventajas desde un punto de vista agronómico y medioambiental. La utilización de este
tipo de compost como materia prima para la elaboración de sustratos de cultivo
genera ciertas dudas por sus características, especialmente cuando provienen de
sistemas de compostaje descentralizado en los que se han compostado restos de
alimentos entre los que se incluyen alimentos de origen animal (carne y/o pescado). El
objetivo del este trabajo es evaluar compost domésticos como componente de
sustratos para cultivo de ornamentales que incluyen distintas proporciones de restos
de alimentos cárnicos. Para este fin se compararon 3 compost domésticos (uno
vegetal y dos con 15% carne) y uno comercial. Los compost fueron caracterizados
mediante análisis de su composición elemental, pH y CE. Cada compost fue mezclado
al 25 y 75 % v/v con sustrato a base de turba (utilizado puro como control). Además
las dos mezclas con mayor CE fueron sometidas a lavados sucesivos, monitorizando
el descenso de salinidad tras cada lavado y la composición elemental del líquido
drenado. Plantas de pensamientos fueron cultivadas en macetas de 2 L con cada uno
de los 11 sustratos indicados. Durante seis semanas de cultivo se midió la biomasa
vegetal, la altura y el número de tallos, el número de flores y el contenido en clorofila
mediante índice colorimétrico SPAD. Las diferencias entre los distintos tratamientos
fueron pequeñas. El lavado previo de los sustratos no modifico significativamente la
respuesta del cultivo. Se concluyen que los sustratos con compost de FORM que
contiene hasta un 15% de restos de alimentos de origen animal no afectan
negativamente al cultivo de pensamientos bajo las condiciones del presente ensayo., Esta investigación ha sido financiada por el proyecto MICYT AGL2012-37815-C05-05.

Acceso cerrado a este documento. No se encuentra disponible para la consulta pública. Depositado en Academica-e para cumplir con los requisitos de evaluación y acreditación académica del autor/a (sexenios, acreditaciones, etc.)., Mediterranean soils, which are carbonate-rich and organic matter-poor, are prone to erosion and important carbon losses due to seasonal changes associated with dry summers and wet winters. The use of thermophilic digested sewage sludge (TSS) in these agricultural systems, as a soil amendment, has been acknowledged as an interesting way to supply organic matter and nutrients. Data on the long-term evaluation of TSS applied to Mediterranean soils are scarce. Moreover, the effect of the application is unpredictable because of the intrinsic variation in the TSS. The scope of this study was to determine whether the continued application of TSS for 20 years leads to increased carbon sequestration in the soil without affecting emissions of greenhouse gases.
To conduct this evaluation, the doses applied since 1992 have been as follows: 40 t ha−1 and 80 t ha−1 every year, and 40 t ha−1 every 3 years, plus annual mineral N fertilization depending on the crop. A control without TSS or mineral fertilization and a treatment with only mineral N fertilizer were also evaluated. In this case, urea was used as the mineral treatment. The TSS doses were applied annually in October, while the mineral was split into one dose around January and another in March. The chemical parameters, greenhouse gas emissions, nitrate and ammonium concentrations of the soil were measured during the crop cycle. The bacterial community and enzymes in the soil were surveyed 15 days after the last annual application and at harvest. Fifteen days after fertilization with TSS and urea, nitrification and denitrification potentials were measured.
The 80 t ha−1 yr−1 dose yielded the most significant increase in total carbon, organic matter content, P2O5, and total nitrogen. This same treatment significantly increased GHG emissions for all gases concerned. Similar results were found in the 40 t ha−1 3yr−1 and urea for CO2 and CO2eq ha−1. TSS application increased soil enzyme activities. According to the microbial diversity results, 80% of the DNA sequences corresponded to 6 main phyla: (from most to least) Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi and Verrucomicrobia with unclassified material making up an average 10.94% of the sequences. The soil microbial community structure only altered with the 80 t ha−1 yr−1 dose. The highest dose of TSS applied in this study resulted in the irreversible lodging of the crop and a concomitant decrease in yield.
In the 40 t ha−1 3yr−1 treatment, interesting similarities were found with urea alone. In summary, rational application of TSS, such as 40 t ha−1 3yr−1 dose, along with urea, trigger a beneficial increase in microbial activity in soil, that ultimately activates soil metabolism and enhances carbon sequestration possibilities, while GHG emissions remain at the same level as with urea alone. The results support the hypothesis that TSS can induce carbon sequestration without increasing GHG emissions. TSS has proven to exert beneficial outcomes under Mediterranean conditions; additionally, its application offers a viable opportunity for converting this by-product into a fertilizer. However, application rates must be adjusted or it should be used together with mineral fertilization., This work was supported by the Spanish Commission of Science and Technology under project number AGL2012-37815-C05-05 and project P08-CVI-03549 from the Consejería de Innovación, Ciencia y Empresa of the Junta de Andalucía.

El crecimiento de la población y sus necesidades de alimentación en las últimas décadas han sido mayoritariamente sustentados por un modelo productivo lineal a escala global basado en consumir recursos y generar residuos. Este modelo en muchas ocasiones ha contribuido de manera crucial al deterioro de agrosistemas y al cambio climático global.
Para mejorar la sostenibilidad de los agrosistemas y mitigar el cambio climático es fundamental potenciar modelos productivos circulares locales basados en aprovechar residuos del entorno como recursos que permitan mejorar la fertilidad y resiliencia de los agrosistemas y desarrollar una agricultura más sostenible.
Es por esto, que esta tesis tiene por objetivo general el estudio del uso continuado de residuos orgánicos en suelos agrícolas como enmiendas.
Esta investigación se ha desarrollado en dos ensayos de larga duración ubicados en Navarra (España) donde se realizan distintos manejos de fertilización con residuos orgánicos. El primero de ellos es una viña de DOC Rioja (Bargota) en la que desde 1998 se aplican anualmente 3 compost diferentes. El segundo ensayo es una rotación cerealista (Arazuri) que desde 1992 recibe anualmente lodos de EDAR a distintas dosis.
Los resultados de estos ensayos muestran un claro efecto beneficioso de la aplicación de distintos residuos orgánicos como fertilizantes en ambos agrosistemas., Azken hamarkadetan biztanleriak eta beren janari beharrak hazkunde ikaragarria jasan dute. Hazkunde hori gehienetan ekoizpen eredu global eta lineal batez asetua izan da. Eredu honetan baliabideak kontsumitzen eta hondakinak sortzen dira neurri gabean. Honen ondorioz, askotan nekazaritza sistemen hondamena eta klima-aldaketa globala eragin ditu.
Nekazaritza sistemen iraunkortasuna hobetzeko eta klima-aldaketan eraginak arintzeko ezinbestekoa da tokiz-tokiko ekonomia zirkularrean oinarritutako ekoizpen ereduak indartzea. Hondakin organikoak ongarri bezala erabiltzea aukera ona da, bai nekazaritza sistemen emankortasuna, eta bai bere erresilientzia handitzeko. Baina epe luzera izan ahal dituen zenbait alde negatibo ebaluatu behar dira.
Hori dela eta, tesi honen helburu orokorra lurzoruan epe luzera hondakin organikoen aplikazio jarraiaren zenbait ingurugiro alde aztertzea da.
Ikerketa hau Nafarroan (Espainian) kokatzen diren epe luzerako ongarri organikoen bi entsaioetan burutua izan da. Lehenengoa Bargotako DOC Errioxako mahatsean, zeinetan 1998az geroztik 3 konpost diferente aplikatzen diren. Bigarrena, Arazuriko zereal errotazio batean zeinean 1992az geroztik urtero EDAR-lohi dosi ezberdin aplikatzen diren.
Entsaio hauetan lortutako emaitzek gai organiko hauek epe luzera erabiltzearen abantailak agerian utzi dituzte., The population growth rate and their diet and the land required to meet this demand has been largely supported by a global model based on a linear economy that consumes resources and generates wastes. This model has often contributed to the deterioration of agricultural systems and global climate change.
The sustainability of agricultural systems can be improved, on one hand, and climate change can be mitigated, on the other, by empowering circular productive models based on local resources and their rational exploitation. If soil fertility is regarded as an important feature of food production, then an important occasion for the contribution of agricultural practices is set to achieve food sustainability.
This research was conducted in two sites in Navarra (Spain) where long-term trials have been established with different fertilization management and by the use of organic wastes, either composted or treated. The first trial was a vineyard situated in the P.D.O. La Rioja, Navarra, in which three different compost have been applied annually since 1992. The second trial is on cereal crops in rotation in Arazuri, Navarra, that have been receiving Treated Sewage Sludge annually since 1992.
The results of this thesis show a clear beneficial effect after organic wastes have been applied to soil as organic amendments in both agricultural systems., Esta tesis doctoral ha sido financiada con una Beca de formación de personal investigador de la Universidad Pública de Navarra (2011- 2015) y ha recibido financiación del Ministerio de Economía y Competitividad (Proyectos: AGL2009-13339-C02-02; AGL2012-37815-C05-05)., Programa Oficial de Doctorado en Agrobiología Ambiental (RD 1393/2007), Ingurumen Agrobiologiako Doktoretza Programa Ofiziala (ED 1393/2007)

This paper presents a three-year pilot experience of a new municipal waste management system developed in Navarre, Spain that integrates composting and hens. The aim of this new system is to motivate the general public to participate more in waste prevention programs. The Composter-Henhouse (CH) is a compact facility comprised of a henhouse and three composters. This is shared by 30 families who provide the organic part of their kitchen waste to feed the hens. Hens help speed up the composting process by depositing their droppings and turning the organic residue into compost. This study assesses the CH in terms of treatment capacity, the technical adequacy of the composting process, the quality and safety of the compost obtained and some social aspects. Over three years, the CH has managed nearly 16.5 tons of organic waste and produced approximately 5600 kg of compost and more than 6000 high-quality fresh eggs. No problems or nuisances have been reported and the level of animal welfare has been very high. The follow up of the composting process (temperature, volume reduction and compost maturity) and a physicochemical and microbiological analysis of the compost have ensured the proper management of the process. The level of involvement and user satisfaction has been outstanding and the project has presented clear social benefits., The study was financially supported by the Spanish Ministry of Science and Technology (projects AGL2012-37815-C05-05 and AGL2015-64582-C3-1-R).

Este estudio presenta un nuevo sistema descentralizado de tratamiento
de residuos orgánicos municipales (FORM): el Avi-Compo. El Avi-Compo es
una reducida instalación, que incluye un pequeño gallinero y dos compostadores,
compartida y utilizada por un colectivo de personas comprometidas,
también, en su mantenimiento. Los participantes aportan la fracción
orgánica de sus residuos, de los que las gallinas se alimentan, contribuyendo,
además, a acelerar el proceso de compostaje gracias a la acción de sus
picos y patas. Los huevos que producen las gallinas se reparten entre los
usuarios del Avi-Compo, favoreciendo la motivación para la separación de
residuos orgánicos en sus casas y para participar en el mantenimiento de la
instalación. Se presentan los resultados de los primeros seis meses de funcionamiento
de una instalación piloto del Avi-Compo situada en Noáin (Navarra).
En total, se ha tratado la fracción orgánica de veintiocho familias voluntarias.
Esta experiencia se considera un éxito por el elevado índice de
participación, el alto nivel de satisfacción de los voluntarios/usuarios, la
gran cantidad de residuos orgánicos tratados, la calidad del compost obtenido,
el confort de las gallinas y la no aparición de incidencias destacables., Este trabajo ha sido subvencionado parcialmente por la Comisión de Ciencia y Tecnología del Gobierno de España (MCyT proyecto AGL2012-37815-C05-05).

Las más recientes políticas europeas en materia de residuos contemplan un sistema jerárquico de opciones de gestión, en el cual las acciones de prevención constituyen la más alta prioridad. Desde los años noventa el compostaje "in situ" a escala doméstica o comunitaria (autocompostaje) se está afirmando como vía de reducción de la generación de residuos en origen, presentando claras ventajas en términos medioambientales, económicos y sociales. Sin embargo, la literatura científica sobre los aspectos operativos del compostaje a pequeña escala cuenta todavía con un número exiguo de publicaciones. El objetivo de la presente tesis doctoral es profundizar en el estudio de aspectos operativos de las técnicas del compostaje a pequeña escala para favorecer su sostenibilidad y difusión como instrumento de prevención de residuos. En la primera parte de la tesis se realizó un "estudio de potencialidades" para identificar los aspectos técnicos a investigar en la parte experimental. Este estudio ha sido desarrollado a través de una revisión bibliográfica de trabajos de investigación, reports de entidades públicas y memorias de proyectos, con especial atención a aspectos medioambientales y económicos, y mediante la posterior realización de un análisis SWOT (DAFO). En este último se identificaron, a través de opiniones de expertos, técnicos gestores, educadores ambientales y participantes en iniciativas de autocompostaje recogidas en conferencias encuestas y entrevistas, los principales elementos de Fortaleza, Debilidad y posibles Amenazas y Oportunidades. Los resultados obtenidos en este estudio han puesto de manifiesto una serie de elementos de incertidumbre, problemas de carácter técnico y dudas sobre el manejo del proceso a pequeña escala, que son objeto de los diferentes ensayos desarrollados en la parte experimental de la tesis. El primer aspecto técnico abordado en la parte experimental ha sido el de determinar en qué difiere el compostaje doméstico del compostaje a escala industrial. Para este fin, se realizaron 4 ensayos comparando el compostaje del mismo tipo de residuo a escala industrial en pilas(> 1300 t) y doméstico en composteras (320 L), en términos de desarrollo del proceso y características del compost obtenido. Los primeros dos ensayos fueron realizados, respectivamente, con residuos agroindustriales y fracción orgánica de residuos municipales (FORM), utilizando el mismo material estructurante y la misma frecuencia de volteo. Durante estos primeros ensayos se observó un limitado desarrollo del proceso de compostaje a escala doméstica, ya que el tamaño del estructurante utilizado era demasiado grueso y la frecuencia de volteo insuficiente para el compostaje en composteras. Posteriormente, se realizaron un tercer y un cuarto ensayo compostando FORM a ambas escalas, modificando, en la escala doméstica, el tamaño del estructurante empleado y la frecuencia de volteo adoptada. En estos 4 ensayos se ha observado una mayor intensidad del proceso en las primeras fases de compostaje en composteras domésticas, afectando positivamente a la evolución del compost, mientras las características químico-fisicas y la madurez de los compost obtenidos al final del proceso fueron similares en ambas escalas. Asimismo se observó una mayor dependencia de la temperatura externa del compostaje en composteras, respecto al proceso realizado en pilas de grandes dimensiones. Adecuando el calendario de volteo y el tamaño de estructurante a escala doméstica se pudieron conseguir prestaciones incluso superiores al compostaje industrial, en términos de desarrollo de temperatura, reducciones de peso y volumen, madurez y composición del compost final. Posteriormente, se han realizados ensayos específicos sobre el proceso de compostaje en composteras domésticas: Por un lado se han evaluado distintos regímenes de alimentación de las composteras, comparando distintas frecuencias con la que se realizan los aportes y distintas cantidades de material orgánico adicionado con cada aporte. Se ha observado un mayor desarrollo de la temperatura y una mayor actividad microbiana durante el compostaje con aportes de mayor tamaño. Por otro lado, se han estudiado los efectos de la aportación de alimentos cárnicos, comparando diferentes mezclas de restos orgánicos iniciales obtenidas combinando dos proporciones distintas de carne/vegetal con dos dosis diferentes de estructurante. La presencia de restos cárnicos ha aumentado la temperatura durante el proceso, mejorando la madurez y el grado de humificación del compost, sin afectar negativamente a su conductividad eléctrica, pH, contenido en metales pesados ni a su fitotoxicidad. Un adecuado manejo del proceso es efectivo para reducir el riesgo microbiológico. A su vez, en otro ensayo se han evaluado cuatro materiales (3 vegetales y 1 mineral) para su utilización como estructurante en composteras domésticas. Las propiedades de los diferentes materiales estructurantes influyeron sobre el desarrollo del proceso afectando a la evolución de las características del compost. Los restos de poda triturados, habitualmente empleados en la práctica del autocompostaje, han sido los que proporcionaron mejores prestaciones en términos de calidad del compost y desarrollo del proceso. Paralelamente, se ha evaluado la capacidad de control del proceso de compostaje a escala doméstica sobre la vitalidad de semillas, mediante dos experimentos. En el primer experimento, se colocaron en el interior de las composteras unos contenedores metálicos con semillas de distintas plantas que fueron retiradas al término del proceso de compostaje para ponerlas a germinar. En el segundo experimento, se incubó compost doméstico en condiciones óptimas para poder observar la eventual germinación de semillas. Se concluye que el proceso de compostaje en composteras, alcanzando temperaturas termófilas, ha sido capaz de controlar la germinación de semillas. No obstante, son necesarios volteos suficientes, que aseguren que todo el material compostado sea sometido a condiciones de proceso. Con el material obtenido en los anteriores experimentos de compostaje se han realizado ensayos de cultivo en macetas, evaluando diferentes compost domésticos como fertilizante (en lechuga y espinaca) y como ingrediente para sustrato de cultivo (en pensamiento). A la luz de los resultados obtenidos en ambos ensayos, es posible concluir que el compost producido a nivel doméstico puede ser utilizado con toda seguridad como fertilizante o en la formulación de sustratos de cultivos, incluso en dosis más elevadas con respecto a compost industriales. Además, se investigó si la trituración de restos de poda, empleados como estructurante, puede constituir una fuente de metales pesados presentes en el compost. Para ello, se ha analizado el material triturado con 15 biotrituradoras móviles (con distintos tamaños, sistemas de corte y alimentación) y se han calculado las posibles concentraciones finales en el compost obtenido. Los materiales triturados presentaron bajos contenidos de metales pesados y su utilización no constituye una fuente significativa de contaminantes para el compost producido a nivel doméstico o comunitario. Finalmente, se ha realizado el seguimiento de un proyecto piloto de compostaje comunitario asistido por gallinas realizado en Noáin (Navarra) en colaboración con el ayuntamiento y 30 familias de dicha localidad. A la luz de los resultados obtenidos en los primeros tres años de funcionamiento, ha sido posible concluir que el manejo del compostaje ha sido técnicamente válido, con un correcto desarrollo del proceso y una alta calidad del compost producido. El sistema propuesto ha conseguido reducir satisfactoriamente una cantidad considerable de residuos orgánicos municipales destinados a la recogida y tratamiento centralizado, proporcionando, además, beneficios económicos, medioambientales y sociales. El autocompostaje en composteras de pequeñas dimensiones se ha revelado como herramienta eficaz para la prevención de residuos orgánicos domiciliarios, presentando, desde un punto de vista técnico, un correcto desarrollo del proceso. El compost obtenido presentó características adecuadas para su utilización doméstica. No obstante, para avalar y potenciar su difusión, sería interesante abordar en futuros estudios también aspectos sociales, demográficos, políticos, económicos y medioambientales asociados a estas prácticas., The most recent European waste policies include a hierarchical system of management options, in which prevention efforts are the highest priority. Since the 1990s, “in-situ” composting on a home or community scale has been asserted as a way of reducing waste generation at source, presenting clear environmental, economic and social advantages. However, there are still few publications to be found in the scientific literature on the operational aspects of small-scale composting. The objective of this doctoral thesis is to look more deeply into these operational aspects of small-scale composting techniques, to promote their sustainability and raise awareness of them as a tool for waste prevention. Composting in small bins is therefore an effective tool for preventing household organic waste, correctly developing the process from a technical perspective. The characteristics of the compost obtained make it suitable for domestic use. However, to support and promote the awareness of this practice, it would be interesting for future studies to address the associated social, demographic, political, economic and environmental aspects., Este trabajo de investigación ha recibido financiación del Ministerio de Economía y Competitividad (Proyectos: AGL2009-13339-C02-02; AGL2012-37815-C05-05). La realización de la presente tesis ha sido posible gracias a la financiación recibida a través de las Ayudas Predoctorales de la Universidad Pública de Navarra (2013-2017)., Programa Oficial de Doctorado en Agrobiología Ambiental (RD 1393/2007), Ingurumen Agrobiologiako Doktoretza Programa Ofiziala (ED 1393/2007)

Ammonium is an important nitrogen (N) source for living organisms, a key metabolite for pH control, and a potent cytotoxic compound. Ammonium is transported by the widespread AMT-Mep-Rh membrane proteins, and despite their significance in physiological processes, the nature of substrate translocation (NH3/NH4+) by the distinct members of this family is still a matter of controversy. Using Saccharomyces cerevisiae cells expressing representative AMT-Mep-Rh ammonium carriers and taking advantage of the natural chemical-physical property of the N isotopic signature linked to NH4+/NH3 conversion, this study shows that only cells expressing AMT-Mep-Rh proteins were depleted in N-15 relative to N-14 when compared to the external ammonium source. We observed N-15 depletion over a wide range of external pH, indicating its independence of NH3 formation in solution. On the basis of inhibitor studies, ammonium transport by nonspecific cation channels did not show isotope fractionation but competition with K+. We propose that kinetic N isotope fractionation is a common feature of AMT-Mep-Rh-type proteins, which favor N-14 over N-15, owing to the dissociation of NH4+ into NH3+ H+ in the protein, leading to N-15 depletion in the cell and allowing NH3 passage or NH3/H+ cotransport. This deprotonation mechanism explains these proteins' essential functions in environments under a low NH4+/K+ ratio, allowing organisms to specifically scavenge NH4+. We show that N-15 isotope fractionation may be used in vivo not only to determine the molecular species being transported by ammonium transport proteins, but also to track ammonium toxicity and associated amino acids excretion., I. A. was supported by a postdoctoral fellowship from the Government of Navarra, Spain (Anabasid outgoing Programme, 2011) and by a postdoctoral fellowship from the Portuguese Fundaçao para a Ciencia e a Tecnologia (SFRH/BPD/90436/2012). A.M.M. is a senior research associate of the Belgian Fonds de la Recherche Scientifique Fonds de la Recherche Scientifique-FNRS (grants CDR J017617F, PDR T011515F, and ARC) and a WELBIO investigator, and M.B. is a scientific research worker supported by WELBIO. This work was also developed in the context of the following projects: PTDC/BIA-BEC/099323/2008 and PTDC/AGR-PRO/115888/2009 to cE3c and FCUL, UID/DTP/04138/2013 to iMed. ULisboa, and AGL2015-64582-C3-1-R and AGL2012-37815-C05-05 to UPNa.