Production of N2O in grass-clover pastures

In organic as well as conventional dairy farming, grass-clover pastures is an important component of the cropping system. This is because grass-clover is an excellent cattle fodder, and because clover has the ability of fixing atmospheric N2. When budgets for N2O emissions are made accord-ing to the IPCC guidelines it is assumed that 1.25 % of added nitrogen is emitted as N2O. This emission factor is used for all nitrogen inputs although the factor relies on experiments with fertilizer and manure, only. The emission factor for biological fixed nitrogen may be lower than 1.25 %, because nitrogen is released only slowly into the soil. However knowledge is very sparse. On the other hand, when the effect of grazing cattle is added the situation might be different. In Denmark organic cattle are supposed to be on grazing fields for at least 150 days a year. Nitrogen returned to the system in urine and dung is likely to locally exceed the needs of the plants and is therefore at risk of being lost as N2O. Thus far, however, there have only been a few detailed estimates of total N2O emissions from grassland livestock productions, and understanding of the factors controlling N2O emissions remains unsatisfactory

N2O emission from grass-clover swards is largely unaffected by recently fixed N2

The contribution of biologically fixed dinitrogen (N2) to the nitrous oxide (N2O) production in grasslands is unknown. To assess the contribution of recently fixed N2 as a source of N2O and the transfer of fixed N from clover to companion grass, mixtures of white clover and perennial ryegrass were incubated for 14 days in a 15N2-enriched atmosphere (0.4 atom% excess). Immediately after labelling, half of the grass-clover pots were sampled for N2 fixation determination, whereas the remaining half were examined for emission of 15N labelled N2O for another eight days using a static chamber method. Biological N2 fixation measured in grass-clover shoots and roots as well as in soil constituted 342, 38 and 67 mg N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. The drop in N2 fixation was most likely due to a severe aphid attack on the clover component. Transfer of recently fixed N from clover to companion grass was detected at 26 and 36 weeks after emergence and amounted to 0.7 ± 0.1 mg N m-2 d-1, which represented 1.7 ± 0.3 % of the N accumulated in grass shoots during the labelling period. Total N2O emission was 91, 416 and 259 μg N2O-N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. Only 3.2 ± 0.5 ppm of the recently fixed N2 was emitted as N2O on a daily basis, thus recently fixed N released via easily degradable clover residues appears to be a minor source of N2O

From N2 fixation to N2O emission in a grass-clover mixture

In organic dairy farming, a major N input to the plant-soil system comes from biological N2 fixation by pasture legumes, but knowledge is sparse on how much of the fixed N2 is lost from the pastures as N2O. Nitrifying and denitrifying bacteria are the main contributors to the N2O production in soils. Currently, no contribution from biological N2 fixation in legume pastures is included in the national N2O inventories, partly because of uncertainties in quantifying the N2 fixation in the pastures (Mosier et al., 1998). According to the guidelines issued by The Intergovernmental Panel on Climate Change (IPCC), inventories for N2O emissions from agricultural soils should be based on the assumption that 1.25 % of added N is emitted as N2O (IPCC, 1997). The standard N2O emission factor of 1.25 % could be considerably unrepresentative for biologically fixed N2. Firstly, only a part of the fixed N is mineralised during the lifetime of the crop. Secondly, the release of inorganic N into the soil occurs slowly. A 15N2-tracer-experiment was initiated on grass-clover grown in pots. The aim was to assess: · the contribution of recently fixed N2 as a source of N2O · the translocation of N from clover to companion grass References IPCC, 1997. Greenhouse gas inventory. Reference manual. Vol. 3. Intergovernmental Panel on Climate Change. Bracknell, UK. Mosier, A. et al. 1998. Nutrient Cycling in Agroecosystems 52, 225-248

Production of N2O in grass-clover pastures

In organic as well as conventional dairy farming, grass-clover pastures is an important component of the cropping system. This is because grass-clover is an excellent cattle fodder, and because clover has the ability of fixing atmospheric N2. When budgets for N2O emissions are made accord-ing to the IPCC guidelines it is assumed that 1.25 % of added nitrogen is emitted as N2O. This emission factor is used for all nitrogen inputs although the factor relies on experiments with fertilizer and manure, only. The emission factor for biological fixed nitrogen may be lower than 1.25 %, because nitrogen is released only slowly into the soil. However knowledge is very sparse. On the other hand, when the effect of grazing cattle is added the situation might be different. In Denmark organic cattle are supposed to be on grazing fields for at least 150 days a year. Nitrogen returned to the system in urine and dung is likely to locally exceed the needs of the plants and is therefore at risk of being lost as N2O. Thus far, however, there have only been a few detailed estimates of total N2O emissions from grassland livestock productions, and understanding of the factors controlling N2O emissions remains unsatisfactory

From N2 fixation to N2O emission in a grass-clover pasture

In organic dairy farming, a major N input to the plant-soil system comes from biological N2 fixation by pasture legumes, but knowledge is sparse on how much of the fixed N2 is lost from the pastures as N2O. Nitrifying and denitrifying bacteria are the main contributors to the N2O production in soils. Currently, no contribution from biological N2 fixation in legume pastures is included in the national N2O inventories, partly because of uncertainties in quantifying the N2 fixation in the pastures (Mosier et al., 1998). According to the guidelines issued by The Intergovernmental Panel on Climate Change (IPCC), inventories for N2O emissions from agricultural soils should be based on the assumption that 1.25 % of added N is emitted as N2O (IPCC, 1997). The standard N2O emission factor of 1.25 % could be considerably unrepresentative for biologically fixed N2. Firstly, only a part of the fixed N is mineralised during the lifetime of the crop. Secondly, the release of inorganic N into the soil occurs slowly. A 15N2-tracer-experiment was initiated on grass-clover grown in pots. The aim was to assess: * the contribution of recently fixed N2 as a source of N2O * the translocation of N from clover to companion grass References IPCC, 1997. Greenhouse gas inventory. Reference manual. Vol. 3. Intergovernmental Panel on Climate Change. Bracknell, UK. Mosier, A. et al. 1998. Nutrient Cycling in Agroecosystems 52, 225-248

Assessing Fish Communities and Habitat Dynamics at the North Platte River-Lake Mcconaughy Interface: Implications for Conservation and Management

The river-reservoir interface (RRI) provides dynamic habitat heterogeneity that influences fish communities within the reservoir and the tributary upstream. However, little is known about the North Platte River-Lake McConaughy interface. Thus, the objectives of this research were to: 1) describe fish assemblages in the North Platte River and relate their temporal differences to water quality and physical habitat parameters; and 2) compare young fish communities collected with different gears in the upper reservoir. Twenty-nine species were collected across four habitat types in the North Platte River above Lake McConaughy. Main and side channel habitats were more consistently available throughout the summer. Backwater habitats declined in abundance, and back eddies disappeared. Species richness and Shannon’s diversity were highest in backwaters. Fish communities were somewhat similar between the habitat types, but some species were more or less abundant in some habitats. Water quality did not differ between habitat types. However, discharge and water temperature appeared to influence community composition. In upper Lake McConaughy, I captured 21 taxa across four sampling gears. Fewer species were captured with the gears used in the earlier time period compared to the gears used later time period. Species richness, Shannon’s diversity, and relative abundance were highest for seines and lowest for tow nets. Boat-mounted electrofishing appeared to be the most efficient gear. Similarities were noted in fish communities between the two time periods, but abundance of individual species varied between time periods. This study provides updated and new information on fish communities in the North Platte River-Lake McConaughy system. Selecting the sampling gear or gears that best meet sampling objectives is important for understanding fish communities in RRIs. With such sampling information, fisheries managers may be able to identify water management strategies that provide habitats for fish communities in unique ecotones such as the RRI

Statistic research on changes in speech due to pedagogic treatment (the accent method)

No abstrac

Polq-Mediated End Joining Is Essential for Surviving DNA Double-Strand Breaks during Early Zebrafish Development

SummaryError-prone repair of DNA double-strand breaks (DSBs) has been postulated to occur through classical non-homologous end joining (NHEJ) in systems ranging from nematode somatic tissues to zebrafish embryos. Contrary to this model, we show that zebrafish embryos mutant for DNA polymerase theta (Polq), a critical component of alternative end joining (alt-EJ), cannot repair DSBs induced by CRISPR/Cas9 or ionizing radiation. In the absence of DSBs, polq mutants are phenotypically normal, but they do not survive mutagenesis and display dramatic differences in the mutation profiles compared with the wild-type. These results show that alt-EJ repair is essential and dominant during the early development of a vertebrate

Inclusión de estudiantes con necesidades educativas especiales en el aula regular

Maestría en Educación - Modalidad VirtualThe purpose of this research was to analyse the functional dynamics of the inclusion process of students with special educational needs within the regular classroom. The research was based on a mixed approach of a descriptive nature. The population and sample were forty (40) students in the fourth and fifth grade of primary school, forty (40) teachers and directors and forty (40) parents, focused in four (4) educational institutions of the department two of them official belonging to the rural area of the island and the other two private located in the urban area. A questionnaire was used as instrument to obtain required information. The questionnaires were validated by three (03) experts and subjected to the Lickert scale to obtain reliability. After the processing of the results, it is established that the educational community (teachers, managers, parents) requires more training in terms of educational inclusion and institutions must improve not only physical but technological infrastructure for the improvement of the quality, access and permanence of students with special educational needs. Finally, it was concluded that the conditions of sustainability, processes and resources are scarce or non-existent for the inclusion processes in the educational institutions. It is evident the lack of preparation of teachers in the topic of inclusion and in methodological strategies for the construction and application of an adequate curriculum in the classroom, and also that it entails to contemplate in the curricular approach, aspects of the ethnic territory.Este trabajo de investigación tuvo como propósito analizar la dinámica funcional del proceso de inclusión de los estudiantes con necesidades educativas especiales dentro del aula regular. La investigación se trabajó bajo un enfoque mixto de tipo descriptivo. La población y muestra la conformaron cuarenta (40) estudiantes los grados de cuarto y quinto de primaria, cuarenta (40) docentes y directivos y cuarenta (40) padres de familia, focalizados dentro de cuatro (4) instituciones educativas del departamento, dos de ellas oficiales pertenecientes al área rural de la isla y las otras dos privadas localizadas en el área urbana. Se utilizó como instrumento un cuestionario validado por tres (03) expertos y la fiabilidad mediante el alfa de Cronbach. Luego del procesamiento de los resultados se logra establecer que la comunidad educativa (docentes, directivos, padres de familia) requieren mayor formación en lo referente a la inclusión educativa y las instituciones deben mejorar en cuanto a infraestructura, no solo física sino tecnológica para el mejoramiento de la calidad, el acceso y la permanencia de los estudiantes. Finalmente se concluyó que las condiciones de sustentabilidad, procesos y recursos son escasos o inexistentes para los procesos de inclusión en las I.E. Es evidente la falta de preparación de los docentes en el tema de inclusión y en estrategias metodológicas para la construcción y aplicación de un adecuado currículo en el aula, y además que conlleve a contemplar en el enfoque curricular, aspectos del territorio étnico