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AbstractAfter dredged sediments have settled in a temporary upland disposal site, ripening starts, which turns waterlogged sediment into aerated soil. Aerobic biological mineralization of organic matter (OM) and chemical oxidation of reduced sulfur compounds are the major biochemical ripening processes. Quantitative data describing these processes are scarce. Therefore, aerobic oxidation and mineralization of five previously anaerobic dredged sediments were studied during a 160‐d laboratory incubation experiment at 30°C. A double exponential decay model could adequately describe sulfur oxidation and OM mineralization kinetics. During the first 7 d of incubation, 23 to 80% of the total sulfur was oxidized, after which no further sulfur oxidation was observed. Oxygen used for sulfur oxidation amounted up to 95% of the total oxygen uptake in the first 7 d and up to 45% of the oxygen uptake during the entire incubation period. Mineralization rates of the rapidly mineralizable OM fractions that degraded during the first 14 to 28 d of incubation were 102 to 103 times higher than the mineralization rates of the slowly mineralizable OM during the remaining period. First‐order mineralization rates of the slowly mineralizable OM were 0.22 × 10−3 to 0.54 × 10−3 d−1 and can be compared with those of terrestrial soils. Yields of biomass on substrate ranged from 0.08 to 0.45 g Cbiomass/g COM and appeared to be higher for rapidly mineralizing OM than for slowly mineralizing OM. The results of this study can be used to optimize conditions during temporary disposal of sediments, to estimate the potential decrease in OM, and for future studies on the possible link between OM mineralization and degradation of hydrophobic organic contaminants.

Land-use change and intensification play a key role in the current biodiversity crisis. The resulting species loss can have severe effects on ecosystem functions and services, thereby increasing ecosystem vulnerability to climate change. We explored whether land-use intensification (i.e. fertilization intensity), plant diversity and other potentially confounding environmental factors may be significantly related to water use (i.e. drought stress) of grassland plants. Drought stress was assessed using δ13C abundances in aboveground plant biomass of 150 grassland plots across a gradient of land-use intensity. Under water shortage, plants are forced to increasingly take up the heavier 13C due to closing stomata leading to an enrichment of 13C in biomass. Plants were sampled at the community level and for single species, which belong to three different functional groups (one grass, one herb, two legumes). Results show that plant diversity was significantly related to the δ13C signal in community, grass and legume biomass indicating that drought stress was lower under higher diversity, although this relation was not significant for the herb species under study. Fertilization, in turn, mostly increased drought stress as indicated by more positive δ13C values. This effect was mostly indirect by decreasing plant diversity. In line with these results, we found similar patterns in the δ13C signal of the organic matter in the topsoil, indicating a long history of these processes. Our study provided strong indication for a positive biodiversity-ecosystem functioning relationship with reduced drought stress at higher plant diversity. However, it also underlined a negative reinforcing situation: as land-use intensification decreases plant diversity in grasslands, this might subsequently increases drought sensitivity. Vice-versa, enhancing plant diversity in species-poor agricultural grasslands may moderate negative effects of future climate change.

The functional trait framework provides a powerful corpus of integrated concepts and theories to assess how environmental factors influence ecosystem functioning through community assembly. While common in plant ecology, this approach is under-used in microbial ecology. After an introduction of this framework in the context of microbial ecology and enzymology, we propose an approach 1) to elucidate new links between soil microbial community composition and microbial traits; and 2) to disentangle mechanisms underlying “total” potential enzyme activity in soil (sum of 7 hydrolase potential activities). We address these objectives using a terrestrial grassland ecosystem model experiment with intact soil monoliths from three European countries (Switzerland, France and Portugal) and two management types (Conventional-intensive and Ecological-intensive), subjected to 4 rain regimes (Dry, Wet, Intermittent and Normal) under controlled conditions in a common climate chamber. We found tight associations between proxies of microbial ecoenzymatic community-weighted mean traits (enzymatic stoichiometry and biomass-specific activity) and community composition, bringing new information on resource acquisition strategy associated with fungi, Gram positive and Gram negative bacteria. We demonstrate that microbial biomass explained most of the total enzyme activity before altered rain regimes, whereas adjustments in biomass-specific activity (enzyme activity per unit of microbial biomass) explained most variation under altered rain regime scenarios. Furthermore, structural equation models revealed that the variation of community composition was the main driver of the variation in biomass-specific enzyme activity prior to rain perturbation, whereas physiological acclimation or evolutionary adaptation became an important driver only under altered rain regimes. This study presents a promising trait-based approach to investigate soil microbial community response to environmental changes and potential consequences for ecosystem functioning. We argue that the functional trait framework should be further implemented in microbial ecology to guide experimental and analytical design.

Potato is one of the main crops grown worldwide under different climatic conditions. Potato is conventionally produced under intensive tillage practices under the same or different soil types. Research has shown some contrasting effects of the tillage practices on the soil properties, crop growth, yield, and quality. Under the reducing available freshwater for food production, soil management practices are more targeting conservation and system sustainability. It is therefore critical to revisit literature on the tillage practices and their impact on the soil, crop, and crop yield. This review presents research results of studies conducted exclusively on potatoes comparing different types of tillage practices and is a valuable source of information for potato growers and scientists as it is not only focused on the impact of tillage practices on soil properties but also on potato tuber yield and grade, tuber specific gravity, and the impact of tillage practices on diseases in potatoes.

AbstractThe objections of organic agriculture against genetic engineering as presented in the 2002 Position Statement of the International Federation of Organic Agriculture Movements (IFOAM) are analysed. The objections can be grouped into three categories: risks to human health and the environment, socio-ethical objections, and incompatibility with the principles of sustainable agriculture. As to threats to human health and the environment it is argued that scientists contradict each other. Socio-ethical objections indicate that farmers should also be free to choose for or against genetic engineering and therefore the free-choice criterion needs to be specified. The argument of violating the independence of the farmer depends on the present economic situation (e.g. power of multinationals) and does not seem to be a consequence of genetic engineering as such. But as genetic engineering is mainly practised by multinational organizations the argument cannot be seen separate from the economic situation. Genetic pollution is a serious issue, but only because the organic movement is against genetic engineering on principle. Once the philosophical and ethical principles behind the organic concept of sustainability are specified (the third category), almost all the objections listed in IFOAM's Position Statement can be reformulated into good reasons for rejecting genetic engineering. The basic principles are: a holistic methodological approach to living nature, the self-organization (self-regulation) of living nature, and the integrity of living organisms.

L'intensification durable a été proposée comme moyen d'atteindre la sécurité alimentaire et de réduire les impacts environnementaux de l'agriculture en se concentrant sur la réduction des écarts de rendement sur les terres agricoles existantes tout en améliorant l'efficacité de l'utilisation des ressources. Il existe un consensus général sur le fait que les régions présentant de grands écarts de rendement peuvent bénéficier le plus d'une intensification durable, mais il n'est pas clair dans quelle mesure cela est durable pour les agriculteurs compte tenu de leurs contraintes actuelles en matière de ressources et de leurs stratégies de subsistance. Ici, nous nous appuyons sur trois études de cas contrastées, pour lesquelles des données détaillées au niveau des champs et des exploitations étaient disponibles pour la décomposition des écarts de rendement, afin d'évaluer le fonctionnement de l'intensification durable des cultures (au niveau des champs) au niveau des exploitations à l'aide d'indicateurs environnementaux et socio-économiques. Bien qu'il existe un grand potentiel d'intensification future (plus de production avec plus d'intrants) de la production céréalière dans le sud de l'Éthiopie, l'utilisation actuelle des intrants dans ces systèmes agricoles n'est pas durable sur les plans économique et environnemental au niveau des exploitations. Il en va de même pour la production de riz dans le centre de Luçon, où une intensification durable (plus de production avec moins d'intrants) peut aider à réduire les écarts de rendement et à améliorer l'efficacité de l'utilisation de l'azote (nue), mais elle n'est pas rentable en raison de la forte dépendance à une main-d' œuvre embauchée coûteuse. Des compromis entre la réduction de l'écart de rendement et la productivité du travail ont également été observés dans les systèmes agricoles susmentionnés. Les fermes arables aux Pays-Bas présentent de faibles écarts de rendement ainsi que des performances économiques, des nue et des excédents d'azote plus élevés que ceux observés dans le sud de l'Éthiopie et le centre de Luçon. Pour améliorer la durabilité environnementale, ces exploitations nécessitent des augmentations de l'efficacité de l'utilisation des ressources et une réduction des impacts environnementaux grâce à une utilisation moindre des intrants (même production avec moins d'intrants). Nous concluons que les investissements publics propices à l'innovation et à une agriculture rentable sont essentiels pour rendre les technologies accessibles et abordables pour les agriculteurs et pour veiller à ce que les écarts de rendement puissent être réduits et que les objectifs de durabilité soient atteints au niveau des exploitations. La intensificación sostenible se ha propuesto como una vía para lograr la seguridad alimentaria y reducir los impactos ambientales de la agricultura, centrándose en reducir las brechas de rendimiento en las tierras agrícolas existentes al tiempo que se mejora la eficiencia en el uso de los recursos. Existe un consenso general de que las regiones con grandes brechas de rendimiento pueden beneficiarse más de la intensificación sostenible, pero no está claro qué tan sostenible es esto para los agricultores dadas sus actuales limitaciones de recursos y estrategias de medios de vida. Aquí, nos basamos en tres estudios de casos contrastantes, para los cuales se disponía de datos detallados a nivel de campo y granja para la descomposición de la brecha de rendimiento, para evaluar cómo funciona la intensificación sostenible de los cultivos (a nivel de campo) a nivel de granja utilizando indicadores ambientales y socioeconómicos. Aunque existe un gran potencial para la intensificación futura (más producción con más insumos) de la producción de cereales en el sur de Etiopía, el uso actual de insumos en estos sistemas agrícolas no es económica y ambientalmente sostenible a nivel de granja. Lo mismo ocurre con la producción de arroz en Luzón Central, donde la intensificación sostenible (más producción con menos insumos) puede ayudar a reducir las brechas de rendimiento y mejorar la eficiencia del uso del N (nue), pero no es rentable debido a la gran dependencia de la costosa mano de obra contratada. También se observaron compensaciones entre el cierre de la brecha de rendimiento y la productividad laboral en los sistemas agrícolas mencionados anteriormente. Las granjas cultivables en los Países Bajos exhiben pequeñas brechas de rendimiento, así como un mayor rendimiento económico, superávit de nue y N en comparación con las observadas en el sur de Etiopía y el centro de Luzón. Para mejorar la sostenibilidad ambiental, estas granjas requieren aumentos en la eficiencia del uso de los recursos y una reducción de los impactos ambientales a través de un menor uso de insumos (mismo producto con menos insumos). Concluimos que las inversiones públicas propicias para la innovación y la agricultura rentable son esenciales para que las tecnologías sean accesibles y asequibles para los agricultores y para garantizar que las brechas de rendimiento se puedan reducir y que los objetivos de sostenibilidad se cumplan a nivel de granja. Sustainable intensification has been proposed as a pathway to achieve food security and reduce environmental impacts of agriculture by focusing on narrowing yield gaps on existing agricultural land while improving resource use efficiencies. There is a general consensus that regions with large yield gaps can benefit most from sustainable intensification but it remains unclear how sustainable this is for farmers given their current resource constraints and livelihood strategies. Here, we draw upon three contrasting case studies, for which detailed data at field and farm levels were available for yield gap decomposition, to assess how sustainable intensification of crops (at field level) works out at farm level using environmental and socio-economic indicators. Although there is large potential for future intensification (more output with more input) of cereal production in southern Ethiopia, current input use in these farming systems is not economically and environmentally sustainable at farm level. The same is true for rice production in Central Luzon where sustainable intensification (more output with less input) can help to narrow yield gaps and improve N use efficiency (NUE) but it is not profitable due to the heavy reliance on costly hired labour. Trade-offs between yield gap closure and labour productivity were also observed in the aforementioned farming systems. Arable farms in the Netherlands exhibit small yield gaps as well as higher economic performance, NUE and N surplus compared to those observed in Southern Ethiopia and Central Luzon. For improving environmental sustainability, these farms require increases in resource-use efficiency and a reduction of the environmental impacts through a lower use of inputs (same output with less input). We conclude that public investments conducive for innovation and profitable farming are essential to make technologies accessible and affordable for farmers and to ensure that yield gaps can be narrowed and sustainability objectives served at the farm level. تم اقتراح التكثيف المستدام كمسار لتحقيق الأمن الغذائي والحد من الآثار البيئية للزراعة من خلال التركيز على تضييق فجوات الغلة على الأراضي الزراعية الحالية مع تحسين كفاءة استخدام الموارد. هناك إجماع عام على أن المناطق التي تعاني من فجوات كبيرة في المحاصيل يمكن أن تستفيد أكثر من التكثيف المستدام ولكن لا يزال من غير الواضح مدى استدامة ذلك بالنسبة للمزارعين نظرًا لقيود الموارد الحالية واستراتيجيات سبل العيش. هنا، نعتمد على ثلاث دراسات حالة متناقضة، حيث كانت البيانات التفصيلية على مستوى الحقل والمزرعة متاحة لتحليل فجوة الغلة، لتقييم كيفية عمل التكثيف المستدام للمحاصيل (على مستوى الحقل) على مستوى المزرعة باستخدام المؤشرات البيئية والاجتماعية والاقتصادية. على الرغم من وجود إمكانات كبيرة للتكثيف المستقبلي (المزيد من الإنتاج مع المزيد من المدخلات) لإنتاج الحبوب في جنوب إثيوبيا، فإن الاستخدام الحالي للمدخلات في هذه النظم الزراعية ليس مستدامًا اقتصاديًا وبيئيًا على مستوى المزرعة. وينطبق الشيء نفسه على إنتاج الأرز في وسط لوزون حيث يمكن أن يساعد التكثيف المستدام (المزيد من المخرجات مع مدخلات أقل) في تضييق فجوات الغلة وتحسين كفاءة الاستخدام (NUE) ولكنه ليس مربحًا بسبب الاعتماد الكبير على العمالة المستأجرة المكلفة. كما لوحظت مفاضلات بين إغلاق فجوة العائد وإنتاجية العمل في النظم الزراعية المذكورة أعلاه. تُظهر المزارع الصالحة للزراعة في هولندا فجوات صغيرة في الغلة بالإضافة إلى أداء اقتصادي أعلى وفائض NUE و N مقارنة بتلك التي لوحظت في جنوب إثيوبيا ووسط لوزون. ولتحسين الاستدامة البيئية، تتطلب هذه المزارع زيادات في كفاءة استخدام الموارد وتقليل الآثار البيئية من خلال استخدام أقل للمدخلات (نفس المخرجات مع مدخلات أقل). نستنتج أن الاستثمارات العامة التي تفضي إلى الابتكار والزراعة المربحة ضرورية لجعل التقنيات في متناول المزارعين وبأسعار معقولة ولضمان تضييق فجوات الغلة وتحقيق أهداف الاستدامة على مستوى المزرعة.

Climate and socio-economic change will affect the land use and the economic viability of Dutch dairy farms. Explorations of future scenarios, which include different drivers and impacts, are needed to perform ex-ante policy assessment. This study uses a bio-economic farm model to assess impacts of climate and socio-economic change on dairy farms in a sandy area in the Netherlands. Farm data from the Farm Accountancy Data Network provided information on the current production levels and available farm resources. First, the farm plans of individual farms were optimized in the current situation to benchmark farms and assess the current scope for improvement. Secondly, simulations for two scenarios were included: a Global Economy with 2. °C global temperature rise (GE/W+) and a Regional Community with 1. °C global temperature rise (RC/G). The impacts of climate change, extreme events, juridical change (including abolishment of milk quota), technological change and price changes were evaluated in separate model runs within the predefined scenarios. We found that farms can increase profit both by intensification and land expansion; the latter especially for medium sized farms (less than 70 cows). Climate change including the effect of increased occurrence of extreme events may negatively affect farm gross margin in the GE/W+ scenario. Lower gross margins are compensated for by the effects of technology and price changes. In contrast with the GE/W+ scenario, climate change has positive impacts on farm profit in RC/G, but less favourable farm input-output price ratios have a negative effect. Technological change is needed to compensate for revenue losses due to higher input prices. In both GE/W+ and RC/G scenarios, dairy farms increase production and the use of artificial fertilizer. Medium sized farms have more options to increase profit than the large farms: they benefit more from the abolishment of the milk quota and better adapt to negative and positive impacts of climate change.While the exact impact of different drivers will always remain uncertain, this study showed that changes in prices, technology and markets have a relatively larger impact than climate change, even when extreme events are taken into account. By using whole farm plans as activities that can be selected, the model is grounded in observations, and it was shown that half of the farms are gross margin maximizers as assumed in the model. The model therefore indicates 'what could happen if', and gives insights in drivers and impacts of dairy farming in the region.