N2O emissions from California farmlands: A review

Of the greenhouse gases emitted from cropland, nitrous oxide (N2O) has the highest global warming potential. The state of California acknowledges that agriculture both contributes to and is affected by climate change, and in 2016 it adopted legislation to help growers reduce emissions of greenhouse gases, explicitly including N2O. Nitrous oxide emissions can vary widely due to environmental and agronomic factors with most emission estimates coming from temperate grain systems. There is, however, a dearth of emission estimates from perennial and vegetable cropping systems commonly found in California\u27s Mediterranean climate. Therefore, emission factors (EFs) specific to California conditions are needed to accurately assess statewide N2O emissions and mitigation options. In this paper, we review 16 studies reporting annual and seasonal N2O emissions. This data set represents all available studies on measured emissions at the whole field scale and on an event basis. Through this series of studies, we discuss how such farm management and environmental factors influence N2O emissions from California agriculture and may serve as a basis for improved EF calculations

Do on-farm natural, restored, managed and constructed wetlands mitigate agricultural pollution in Great Britain and Ireland?: a systematic review

Wetlands in agricultural landscapes offer a number of benefits to the landscape function in which they are set, reducing nutrient runoff, providing additional habitat mosaics and offering various ecosystem services. They require careful planning and maintenance in order to perform their optimum design function over a prolonged period of time. They should be treated as functional units of farm infrastructure rather than fit-and-forget systems. A high priority topic within the Department for Environment, Food and Rural Affairs (DEFRA) water quality programme is the mitigation of pollution from agriculture. This programme was set up to meet the requirements of the European Water Framework Directive (WFD) EU (2000). Nutrient loss from agricultural land has been suggested as a major cause of elevated nutrient concentrations in surface waters in the UK. Nitrogen (N) and phosphorus (P) are of particular concern as an excess of either nutrient can lead to eutrophication of freshwater systems and coastal waters. Agriculture has also been identified as a significant source of suspended sediment (SS) concentrations in UK rivers and agriculturally derived sediment has been identified as a source of increased bed-sediment P concentrations in rivers. High bed sediments loads have other negative impacts, such as clogging river gravels reducing fish spawning. There is considerable evidence in the published and grey literature that wetlands have the ability to remove nutrients and sediment and thus reduce the load on receiving waters. Wetlands have also been reported to perform other ecosystem services, such as reducing floods, supporting biodiversity and sequestering carbon. A policy to promote the conservation, management, restoration or construction of wetlands could help to mitigate the impacts of N, P and SS from agriculture delivering requirements of WFD through Catchment Sensitive Farming following an Ecosystem Approach and Catchment Based Approach promoted by Defra. It could also meet other commitments such as implementing the Ramsar and Biodiversity Conventions to which the UK is a signatory. However, the term wetlands covers a wide range of habitat types and it is important that policy makers are provided with accurate, robust and independently reviewed information on the degree to which different types of wetland perform these services under different circumstances, so that policy can most best targeted. This systematic review assesses the available evidence on the performance of various wetland types on farms to reduce nutrient input and suspended sediments to receiving waters. It provides a defensible evidence base on which to base policy. The studies reviewed cover different input loads and the analysis compares performance of these wetland systems in respect of % reduction efficiency. In England and Wales, Defra, working closely with the Environment Agency and Natural England, has commissioned this systematic review on how effective, and what influences the effectiveness of wetlands at mitigating N, P and SS inputs from agriculture to receiving freshwater in the United Kingdom and Ireland

Early season N2O emissions under variable water management in rice systems: source-partitioning emissions using isotope ratios along a depth profile

Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotope ratios of emitted and pore air N2O (δ15N, δ18O and site preference, SP) over the course of 6 weeks in the early rice growing season. Isotope ratio measurements were coupled with simultaneous measurements of pore water NO−3, NH+4, dissolved organic carbon (DOC), water-filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP × δ18O-N2O and SP × δ15N-N2O in simple two end-member mixing models to evaluate the contribution of nitrification, denitrification and fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded + alternate wetting and drying (DS-AWD) treatment relative to water-seeded + alternate wetting and drying (WS-AWD) and water-seeded + conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction, while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO−3 availability in all treatments; thus, water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO−3 and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in 15N fertilizer labeling studies in rice systems and show promise for the use of dual isotope ratio mixing models to estimate N2 losses.ISSN:1726-4170ISSN:1726-417

In-depth analysis of N2O fluxes in tropical forest soils of the Congo Basin combining isotope and functional gene analysis

Primary tropical forests generally exhibit large gaseous nitrogen (N) losses, occurring as nitric oxide (NO), nitrous oxide (N2O) or elemental nitrogen (N2). The release of N2O is of particular concern due to its high global warming potential and destruction of stratospheric ozone. Tropical forest soils are predicted to be among the largest natural sources of N2O; however, despite being the world’s second-largest rainforest, measurements of gaseous N-losses from forest soils of the Congo Basin are scarce. In addition, long-term studies investigating N2O fluxes from different forest ecosystem types (lowland and montane forests) are scarce. In this study we show that fluxes measured in the Congo Basin were lower than fluxes measured in the Neotropics, and in the tropical forests of Australia and South East Asia. In addition, we show that despite different climatic conditions, average annual N2O fluxes in the Congo Basin’s lowland forests (0.97 ± 0.53 kg N ha−1 year−1) were comparable to those in its montane forest (0.88 ± 0.97 kg N ha−1 year−1). Measurements of soil pore air N2O isotope data at multiple depths suggests that a microbial reduction of N2O to N2 within the soil may account for the observed low surface N2O fluxes and low soil pore N2O concentrations. The potential for microbial reduction is corroborated by a significant abundance and expression of the gene nosZ in soil samples from both study sites. Although isotopic and functional gene analyses indicate an enzymatic potential for complete denitrification, combined gaseous N-losses (N2O, N2) are unlikely to account for the missing N-sink in these forests. Other N-losses such as NO, N2 via Feammox or hydrological particulate organic nitrogen export could play an important role in soils of the Congo Basin and should be the focus of future research

Re-Framing the Picture: An International Comparative Assessment of Gender Equity Policies in the Film Sector: Full Report Gender Equity Policy (GEP) Analysis Project

Re-Framing the Picture presents research from the “Gender Equity Policy (GEP) Analysis” project. Building on a substantial corpus of studies and data evidencing the long history of gender inequity in the international film sector, the international team of researchers located in Germany, the UK and Canada has designed an innovative, interdisciplinary approach with the aim to “assess, understand, and model the impact of gender equity policies (GEP) in the film industry”. To re-frame the picture of gender equity in film industries, they studied the policies, practices and norms that constrain equitable industry structures. The report presents in-depth insights from three different perspectives: The Policies, the Number, and the Networks. The researchers combine an in-depth analysis of existing gender equity policies, using a specifically designed policy analysis framework and interviews with industry experts, with a quantitative analysis that looks more closely at industry data and the structures it reveals. Finally, a social network approach helps understand how different interventions might reduce the dominance of men in the three case film industries (Germany, the UK and Canada) by modelling the impact of hypothetical policies. They find that 1) fighting gender inequity remains a long-haul endeavour, 2) no one-size-fits-all solution exists, 3) policies need to be intentional and structural, 4) and we should expand the reach of policies that make access to, for instance, funding or awards nominations dependent on progress towards gender equity

Early season N2O emissions under variable water management in rice systems: source-partitioning emissions using isotope ratios along a depth profile

Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase N2O and decrease nitrogen use efficiency. In a field experiment with three water management treatments, we measured N2O isotope ratios of emitted and pore air N2O (delta N-15, delta O-18 and site preference, SP) over the course of 6 weeks in the early rice growing season. Isotope ratio measurements were coupled with simultaneous measurements of pore water NO3-, NH4+, dissolved organic carbon (DOC), water-filled pore space (WFPS) and soil redox potential (Eh) at three soil depths. We then used the relationship between SP x delta O-18-N2O and SP x delta N-15-N2O in simple two end-member mixing models to evaluate the contribution of nitrification, denitrification and fungal denitrification to total N2O emissions and to estimate N2O reduction rates. N2O emissions were higher in a dry-seeded+alternate wetting and drying (DS-AWD) treatment relative to water-seeded+alternate wetting and drying (WS-AWD) and water-seeded+conventional flooding (WS-FLD) treatments. In the DS-AWD treatment the highest emissions were associated with a high contribution from denitrification and a decrease in N2O reduction, while in the WS treatments, the highest emissions occurred when contributions from denitrification/nitrifier denitrification and nitrification/fungal denitrification were more equal. Modeled denitrification rates appeared to be tightly linked to nitrification and NO3- availability in all treatments; thus, water management affected the rate of denitrification and N2O reduction by controlling the substrate availability for each process (NO3- and N2O), likely through changes in mineralization and nitrification rates. Our model estimates of mean N2O reduction rates match well those observed in N-15 fertilizer labeling studies in rice systems and show promise for the use of dual isotope ratio mixing models to estimate N-2 losses

The relative contributions of speechreading and vocabulary to deaf and hearing children's reading ability

Background Vocabulary knowledge and speechreading are important for deaf children's reading development but it is unknown whether they are independent predictors of reading ability. Aims This study investigated the relationships between reading, speechreading and vocabulary in a large cohort of deaf and hearing children aged 5 to 14 years. Methods and procedures 86 severely and profoundly deaf children and 91 hearing children participated in this study. All children completed assessments of reading comprehension, word reading accuracy, speechreading and vocabulary. Outcomes and results Regression analyses showed that vocabulary and speechreading accounted for unique variance in both reading accuracy and comprehension for deaf children. For hearing children, vocabulary was an independent predictor of both reading accuracy and comprehension skills but speechreading only accounted for unique variance in reading accuracy. Conclusions and implications Speechreading and vocabulary are important for reading development in deaf children. The results are interpreted within the Simple View of Reading framework and the theoretical implications for deaf children's reading are discussed

A multi-site review of policies affecting opportunities for children with developmental disabilities to become bilingual

This review of special education and language-in-education policies at six sites in four countries (Canada, United States, United Kingdom, and Netherlands) aimed to determine the opportunities for bilingualism provided at school for children with developmental disabilities (DD). While research has demonstrated that children with DD are capable of learning more than one language (see Kay Raining Bird, Genesee, & Verhoeven, this issue), it was not clear whether recent policies reflect these findings. The review, conducted using the same protocol across sites, showed that special education policies rarely addressed second language learning explicitly. However, at all sites, the policies favoured inclusion and educational planning based on individual needs, and thus implied that students with DD would have opportunities for second language learning. The language-in-education policies occasionally specified the support individuals with special needs would receive. At some sites, policies and educational options provided little support for minority languages, a factor that could contribute to subtractive bilingualism. At others, we found stronger support for minority languages and optional majority languages: conditions that could be more conducive to additive bilingualism