Natural abundance analysis of the role played by 15 N as indicator for the certification of organic-system deriving food.

BACKGROUND: The natural abundance of stable isotope 15 N (δ15 N) in production systems has emerged as an alternative to distinguish organic products from conventional ones. This study evaluated the use of δ15 N values recorded for nitrogen fertilizers, soil and plant tissue in order to set the differences between organic and conventional agricultural production systems applied to rice, potatoes, apple and banana crops. RESULTS: Values of δ15 N recorded for N sources ranged from +5.58‰ to +18.27‰ and from -3.55‰ to +3.19‰ in organic and synthetic fertilizers, respectively. Values recorded for δ15 N in food from organic rice, potatoes and banana farms were higher than values recorded for δ15 N in conventional farms; the same was observed for values recorded for δ15 N in leaves from the four crops. CONCLUSION: Results have allowed for differentiation between production systems due to values of δ15 N recorded in leaves of all crops and food, for rice, potatoes and banana trees. © 2021 Society of Chemical Industry.

Changes in chemical composition of cover crops residue during decomposition / Mudanças na composição química dos resíduos culturais de plantas de cobertura durante a decomposição

Crop residues decomposition are controlled by chemical tissue components. This study evaluated changes on plant tissue components, separated by the Van Soest partitioning method, during cover crop decomposition. The Van Soest soluble fraction was the first to be released from the crop residues, followed by cellulose and hemicellulose. Lignin was the crop residue component that suffered the least degradation, and for certain crop residue types, lignin degradation was not detected. The degradation of the main components of crop residues (soluble fraction, cellulose, hemicellulose and lignin) is determined by the chemical and structural composition of each fraction.

A decomposição de resíduos culturais é controlada pela composição química do tecido vegetal. O objetivo deste estudo foi avaliar as alterações que ocorrem nos componentes do tecido vegetal, separados pelo fracionamento de Van Soest, durante a decomposição de plantas de cobertura. A fração solúvel foi a primeira a ser liberada dos resíduos culturais, seguida pela celulose e hemicelulose. A lignina foi o componente dos resíduos culturais de menor degradação, sendo que em alguns resíduos culturais não foi possível detectar a degradação deste componente. A degradação dos principais componentes dos resíduos culturais (fração solúvel, celulose, hemicelulose e lignina) é determinada pela composição química e estrutural de cada uma destas frações.

Greenhouse gas emissions and global warming potential from biofuel cropping systems fertilized with mineral and organic nitrogen sources.

Non-legume bioenergy crops can be fertilized with animal manures instead of mineral fertilizers, but the simultaneous application of carbon (C) and nitrogen (N) with manures can increase nitrous oxide (N2O) emissions. On the other hand, manure could increase soil organic C stocks and partly offset greenhouse gas (GHG) emissions and global warming potential (GWP) of crop systems. We performed a two-year study in a biofuel cropping system with sunflower and canola to examine the effects of manure fertilization on grain yields and N use efficiency of crops, and on GWP and GHG intensity (GHGI) in no-till soils under subtropical conditions. The GWP and GHGI were calculated from measured methane (CH4) and N2O emissions and soil organic C stock change, and from estimated carbon dioxide emissions associated with agricultural inputs and farm operations. The following treatments were tested: (i) mineral fertilizer (MF); (ii) poultry manure (PM); (iii) pig deep-litter (PDL); and (iv) no-N control. The application rate of each treatment was adjusted to provide 60 kg available N ha-1 to crops. Grain yield and N accumulated by sunflower and canola were greater in fertilized treatments than in the control, and did not differ among N sources. However, crop N use efficiency was on average 50% lower with manures than MF. CH4 emissions were not affected by N sources, but N2O emissions increased as follows: control (1.37) < MF (2.04) < PDL (4.12) < PM (4.95 kg N ha-1). On the other hand, soil organic C stocks increased more rapidly with manures than MF, resulting in significantly lower GWP and GHGI with manures than MF after two years. These results indicate that animal manures can replace MF as the main source of N to non-legume oil crops and reduce net GHG emissions in biofuel cropping systems under subtropical conditions.

Winter-Season Gaseous Nitrogen Emissions in Subtropical Climate: Impacts of Pig Slurry Injection and Nitrification Inhibitor.

Controlling nitrogen (N) losses from pig slurry (PS) is a challenge under no-till because amendments are left on the soil surface. We investigated the potential of shallow injection of PS, with and without addition of the nitrification inhibitor dicyandiamide (DCD), to abate gaseous ammonia (NH) and nitrous oxide (NO) emissions in winter crops in subtropical soils. Injection was compared with surface broadcasting of PS, with and without DCD. The significance of winter season on annual NO emissions was assessed. Injecting PS reduced NH volatilization compared with surface application. However, this reduction was partly offset because NO emissions increased by 77% (+1.53 kg NO-N ha) when PS was injected. Adding DCD to injected PS reduced NO emission below levels of surface-broadcast PS without the inhibitor, indicating that DCD may be a management option when injecting PS. Compared with a reference urea treatment, PS without DCD increased cumulative NO emissions 5.7-fold (from 613 to 3515 g NO-N ha) when injected, and 3.2-fold (from 613 to 1980 g NO-N ha) when surface applied. Adding DCD significantly reduced emissions with injected PS, whereas reduction was not always significant with surface-applied PS. Nitrous oxide emissions during the winter cropping season contributed 30 to 44% of annual emissions, indicating that controlling gaseous N losses in that season is required to reduce the environmental footprint of the whole cropping system. Overall, combining PS injection with DCD was an efficient practice for reducing winter-season gaseous N losses from no-till soils under subtropical climate.

Influence of summer crop residues on 15N present in organic matter fractions under two lowland soils / Influência de resíduos de culturas de verão sobre o 15 N em frações da matéria orgânica de dois solos de terras baixas

ABSTRACT: The state of Rio Grande do Sul has about 20% of the total area as lowland soils, suitable for flooded rice (Oryza sativa). In order to mitigate damage caused by rice monoculture, new crops such as sorghum (Sorghum bicolor) and soybean (Glycine max) have been cultivated in these areas. With different qualities of crop residues, it is expected a change in soil organic matter (SOM) dynamics and consequently, nitrogen (N) availability. The objective of this study was to evaluate the influence of rice, soybean and sorghum crop residues on the N present in physical fractions of SOM of two lowland soils, using labeled 15N technique, under incubation for 180 days in aerobic condition and more 180 days in anaerobic condition. At 30, 180 and 360 days of incubation the remaining N of the plant residues and N destination from the residues in both soils were quantified in the physical fractions of SOM >250 μm, 250-53 μm and <53 μm. The soil with higher amount of clay+silt received a larger quantity of 15N from residues, while flooding of the soil after 180 days caused a loss of N added to the soil by the soybean and sorghum residues. In general, larger amounts of 15N were reported in the fraction <53 μm, associated with clay minerals, throughout the incubation period. These N losses should be considered in N fertilization for the following crops in rotation with flooded rice.

RESUMO: O Rio Grande do Sul possui cerca de 20% da área total de solos de terras baixas, propícias para o cultivo do arroz (Oryza sativa) irrigado por inundação. Buscando mitigar danos ocasionados com o monocultivo de arroz, novas culturas, como o sorgo (Sorghum bicolor) e a soja (Glycine max), têm sido cultivadas nestas áreas. Com diferentes qualidades de resíduos culturais, espera-se uma alteração na dinâmica da matéria orgânica do solo (MOS) e, consequentemente, do nitrogênio (N). O objetivo deste estudo foi avaliar a influência de resíduos culturais de arroz, soja e sorgo na quantidade de N em frações físicas da MOS de dois solos de terras baixas, utilizando a técnica de marcação isotópica de 15N das culturas e uma incubação por um ciclo de 180 dias em condição aeróbica e mais 180 dias em condição anaeróbica. Aos 30, 180 e 360 dias de incubação foi quantificado o N remanescente dos resíduos vegetais e destino do N proveniente dos resíduos nos dois solos em frações físicas da MOS >250 μm, 250-53 μm e <53 μm. O solo com maior quantidade de argila+silte recebeu maior quantidade de 15N dos resíduos, enquanto que o alagamento do solo após 180 dias de incubação ocasionou uma perda do N adicionado ao solo pelos resíduos de soja e sorgo. De maneira geral, foram encontradas maiores quantidades de 15N na fração <53 μm, associado aos argilominerais. As perdas de N devem ser consideradas na adubação nitrogenada para as culturas sequentes nos sistemas de rotação de culturas com arroz irrigado.

Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2 O emissions.

Simulation models are extensively used to predict agricultural productivity and greenhouse gas emissions. However, the uncertainties of (reduced) model ensemble simulations have not been assessed systematically for variables affecting food security and climate change mitigation, within multi-species agricultural contexts. We report an international model comparison and benchmarking exercise, showing the potential of multi-model ensembles to predict productivity and nitrous oxide (N2 O) emissions for wheat, maize, rice and temperate grasslands. Using a multi-stage modelling protocol, from blind simulations (stage 1) to partial (stages 2-4) and full calibration (stage 5), 24 process-based biogeochemical models were assessed individually or as an ensemble against long-term experimental data from four temperate grassland and five arable crop rotation sites spanning four continents. Comparisons were performed by reference to the experimental uncertainties of observed yields and N2 O emissions. Results showed that across sites and crop/grassland types, 23%-40% of the uncalibrated individual models were within two standard deviations (SD) of observed yields, while 42 (rice) to 96% (grasslands) of the models were within 1 SD of observed N2 O emissions. At stage 1, ensembles formed by the three lowest prediction model errors predicted both yields and N2 O emissions within experimental uncertainties for 44% and 33% of the crop and grassland growth cycles, respectively. Partial model calibration (stages 2-4) markedly reduced prediction errors of the full model ensemble E-median for crop grain yields (from 36% at stage 1 down to 4% on average) and grassland productivity (from 44% to 27%) and to a lesser and more variable extent for N2 O emissions. Yield-scaled N2 O emissions (N2 O emissions divided by crop yields) were ranked accurately by three-model ensembles across crop species and field sites. The potential of using process-based model ensembles to predict jointly productivity and N2 O emissions at field scale is discussed.

Crambe (Crambe abyssinica) and sunflower (Helianthus annuus) protein concentrates: production methods and nutritional properties for use in fish feed.

The purpose of this study was to develop and improve protein concentration techniques for two industrial by-products with the potential for use in fish feed. In particular, we chemically characterized crambe meal and sunflower meal and their protein concentrates. Three different protein concentration methods were tested: isoelectric pH (pHi), acid pH and alkaline pH. For crambe and sunflower meals extraction using the pHi method was most efficient in terms of protein yield and crude protein content in the concentrates; this method also increased lysine and methionine content in the concentrates. The water holding capacity of the sunflower protein concentrate was greater than that of the crambe protein concentrate. The crambe protein concentrate had a foam-formation capacity of 15%, which stabilized at 6% after 90 minutes. The protein concentration method also reduced total phenolic content by approximately 50% in the concentrates compared with the meals. Therefore, we conclude that protein concentration using the pHi method is the most efficient technique for crambe and sunflower meals, and the use of this technique can decrease total phenolic compounds while improving meal quality for fish feeding.

Crambe (Crambe abyssinica) and sunflower (Helianthus annuus) protein concentrates: production methods and nutritional properties for use in fish feed

ABSTRACT The purpose of this study was to develop and improve protein concentration techniques for two industrial by-products with the potential for use in fish feed. In particular, we chemically characterized crambe meal and sunflower meal and their protein concentrates. Three different protein concentration methods were tested: isoelectric pH (pHi), acid pH and alkaline pH. For crambe and sunflower meals extraction using the pHi method was most efficient in terms of protein yield and crude protein content in the concentrates; this method also increased lysine and methionine content in the concentrates. The water holding capacity of the sunflower protein concentrate was greater than that of the crambe protein concentrate. The crambe protein concentrate had a foam-formation capacity of 15%, which stabilized at 6% after 90 minutes. The protein concentration method also reduced total phenolic content by approximately 50% in the concentrates compared with the meals. Therefore, we conclude that protein concentration using the pHi method is the most efficient technique for crambe and sunflower meals, and the use of this technique can decrease total phenolic compounds while improving meal quality for fish feeding.

Dicyandiamide as nitrification inhibitor of pig slurry ammonium nitrogen in soil / Dicianodiamida como inibidor da nitrificação do nitrogênio amoniacal de dejetos líquidos de suínos no solo

ABSTRACT: Inhibition of nitrification of ammoniacal nitrogen pig slurry after its application to the soil can mitigate nitrogen (N) losses by nitrate (NO3-) denitrification and leaching, with economical and environmental benefits. However, the use of this strategy is incipient in Brazil and, therefore, requires further assessment. The aim of this study was to evaluate the efficiency of dicyandiamide (DCD) nitrification inhibitor in slowing the nitrification of ammoniacal N applied to the soil with pig slurry (PS). For this, incubation was performed in laboratory, where nitrification was assessed by NO3- accumulation in the soil. Rates of 2.8, 5.7 and 11.3kg DCD ha-1 were compared, being applied to the soil during PS addition. Nitrification was inhibited by DCD, and inhibition magnitude and duration depended on DCD applied rate. At a dose of 11.3kg ha-1 DCD, nitrification was completely inhibited in the first 12 days. During the first month after PS application, each 2.8kg of DCD increase applied per hectare promoted NO3--N reduction in the soil of 13.3kg ha-1, allowing longer ammoniacal N maintenance in the soil.

RESUMO: A inibição da nitrificação do nitrogênio amoniacal dos dejetos de suínos, após sua aplicação no solo, poderá mitigar as perdas de nitrogênio (N) por desnitrificação e lixiviação de nitrato (NO3-), com benefícios econômicos e ambientais. Todavia, o uso dessa estratégia é incipiente no Brasil e, por isso, necessita ser avaliada. O objetivo deste trabalho foi verificar a eficiência do inibidor de nitrificação dicianodiamida (DCD) em retardar a nitrificação do N amoniacal aplicado ao solo com dejetos líquidos de suínos (DLS). Para isso, foi realizada uma incubação no laboratório, quando a nitrificação foi avaliada através do acúmulo de NO3- no solo. Foram comparadas as doses de 2,8, 5,7 e 11,3kg de DCD ha-1, aplicadas ao solo no momento da adição dos DLS. A nitrificação foi inibida pela DCD, sendo que a magnitude e a duração da inibição foram dependentes da dose de DCD aplicada. Na dose de 11,3kg de DCD ha-1, a nitrificação foi completamente inibida nos primeiros 12 dias. Durante o primeiro mês após a aplicação dos dejetos, cada incremento de 2,8kg de DCD aplicado por hectare promoveu uma redução no aparecimento de N-NO3- no solo de 13,3kg ha-1, o que permite a manutenção de N amoniacal por mais tempo no solo.

Injection of Dicyandiamide-Treated Pig Slurry Reduced Ammonia Volatilization without Enhancing Soil Nitrous Oxide Emissions from No-Till Corn in Southern Brazil.

There is a lack of information on how placement in soil and nitrification inhibitors affects nitrous oxide (NO) and ammonia (NH) emissions from pig slurry (PS) applied under no-till (NT) conditions. Our objective was to determine the impact of injecting PS and treating it with the nitrification inhibitor dicyandiamide (DCD) on NH and NO emissions from soils under NT in subtropical southern Brazil. The emissions of these gases were compared for shallow (∼ 10 cm) injection and surface broadcasting of PS with and without DCD (8.1-10.0 kg ha; 6.5-8.4% of applied NH-N). Measurements were made at two sites during two summer growing seasons under NT corn crops. Injection reduced NH volatilization by 70% but increased NO emissions 2.4-fold (from 2628 to 6198 g NO N ha) compared with surface broadcast application. Adding DCD to PS inhibited nitrification and reduced NO emissions by an average of 28% (730 g NO-N ha) for surface broadcast and 66% (4105 g NO-N ha) for injection but did not increase NH volatilization. Consequently, NO emission factors were much higher for injection (3.6%) than for surface broadcast (1.3%) application and were reduced (0.9%) when DCD was added to injected PS. In conclusion, the injection of DCD-treated slurry is a recommendable practice for reducing NH and NO emissions when applying PS on NT corn in southern Brazil.

Volatilização de amônia e emissão de óxido nitroso após aplicação de dejetos líquidos de suínos em solo cultivado com milho / Ammonia volatilization and nitrous oxide emissions following soil application of pig slurry in corn

As perdas de nitrogênio (N) através de emissões gasosas de amônia (NH3) e óxido nitroso (N2O) após a aplicação de dejetos líquidos de suínos (DLS) no solo é um assunto ainda pouco estudado no Brasil, sobretudo em plantio direto. Diante disso, o objetivo desse trabalho foi avaliar, em condições de campo, a volatilização de NH3 e a emissão de N2O após a aplicação de DLS no milho, com e sem a presença de palha de aveia preta na superfície do solo. Os tratamentos avaliados para medir a emissão de N2O, durante 90 dias, foram: T1 - Solo (testemunha); T2 - Solo + DLS; T3 - Solo + Palha; T4 - Solo + Palha + DLS. Já a volatilização de NH3 foi quantificada durante 12 dias, somente nos três últimos tratamentos. Os DLS, na dose de 60m³ ha-1, foram aplicados ao solo, antecedendo a semeadura do milho, em delineamento experimental de blocos ao acaso, com três repetições. A presença da palha na superfície do solo reduziu as perdas de NH3 em 34%, porém potencializou as emissões de N2O após a aplicação dos DLS, as quais aumentaram em 167%. Os maiores fluxos de N2O ocorreram durante os primeiros 40 dias após a aplicação dos DLS sempre após a ocorrência de chuvas e/ou irrigações.

The nitrogen (N) losses through gaseous emissions of ammonia (NH3) and nitrous oxide (N2O) after pig slurry (PS) application in soil is a subject still little studied in Brazil, especially under no-till conditions. Therefore, the objective of this study was to evaluate, under field conditions, the NH3 volatilization and the N2O emission after PS application in corn, with and without surface oat straw. The treatments for measuring N2O emissions, during 90 days, were: T1-unamended soil (control), T2 - Soil + PS, T3 - Soil + oat straw and T4 - Soil + PS + oat straw. The NH3 volatilization was quantified only in the last three treatments. PS, at the dose 60m³ ha-1, was applied prior the sowing of corn, in a randomized design, with three replications. Oat straw on the soil surface reduced NH3 volatilization by 34%, but enhanced N2O emission by 167%. The higher N2O fluxes occurred during the first 40 days after PS addition, always after rain and/or irrigation events.

Redução na velocidade da nitrificação no solo após aplicação de cama de aviário com dicianodiamida / Reduction of the nitrification rate in the soil after addition of poultry manure with dicyandiamide

A rápida nitrificação do nitrogênio (N) amoniacal de fontes orgânicas e minerais no solo pode resultar em perdas de nitrato (NO3-) para o ambiente. Uma estratégia para a redução dessas perdas envolve o uso de inibidores de nitrificação. O objetivo do presente trabalho foi o de avaliar, em condições de laboratório, a eficiência da dicianodiamida (DCD), presente no produto Agrotain® Plus (AP), em inibir a nitrificação do N amoniacal de cama de aviário (CA) no solo. Foram avaliados cinco tratamentos, sendo um com CA incorporada ao solo, três com CA incorporada ao solo com AP, nas doses de 3,5, 7,0 e 14,0kg ha-1, além de um tratamento somente com solo. A nitrificação foi monitorada através da determinação periódica dos teores de NH4+ e NO3 no solo durante 69 dias. A maior taxa de nitrificação ocorreu no tratamento em que a CA foi incorporada ao solo sem AP. As doses de 3,5 e 7,0kg de AP ha-1 inibiram parcialmente a nitrificação do N amoniacal da CA na fase inicial da incubação, perdendo a eficiência em inibir esse processo no período entre 12 e 27 dias. O tratamento com a maior dose de AP (14kg ha-1) foi aquele em que a DCD exerceu maior efeito inibitório da nitrificação, preservando maior quantidade de NH4+ e retardando o aparecimento de NO3- no solo. Os resultados deste trabalho indicam que a DCD, contida no Agrotain® Plus, reduz a taxa de nitrificação do N amoniacal da CA no solo, o que poderá contribuir à redução das perdas de NO3- para o ambiente.

The fast nitrification of ammoniacal nitrogen (N) of organic and mineral sources in soil can result in losses of nitrate (NO3-) to the environment. One strategy to reduce these losses involves the use of nitrification inhibitors. The objective of this study was to evaluate, in laboratory conditions, the efficiency of Agrotain® Plus (AP), which contains dicyandiamide (DCD), as a nitrification inhibitor of ammoniacal nitrogen from poultry manure (PM) in soil. Were evaluated five treatments, one with PM incorporated into the soil, three with PM incorporated into the soil with AP at the doses of 3.5, 7.0 e 14.0kg ha-1 and one treatment without PM and AP. Nitrification was monitored by measuring changes in soil mineral N (NH4+ and NO3-) periodically over 69 days. The highest rate of nitrification occurred in the treatment in which PM was incorporated into the soil without AP. The doses of 3.5 and 7.0kg ha-1 of AP inhibited partially the nitrification of ammoniacal nitrogen of PM in the initial phase of incubation, losing the ability to inhibit this process in the period between 12 and 27 days. The treatment with the higher dose of AP (14kg ha-1) was on in which the DCD exerted more inhibitory effect on nitrification, preserving most NH4+ and delaying the onset of NO3- in soil. The results of this study indicate that the DCD, contained in the Agrotain® Plus, reduces the nitrification rate of ammoniacal nitrogen from PM in soil, that may contribute to reduce NO3- losses to the environment.

Liberação do N em solos de diferentes texturas com ou sem adubos orgânicos / N release in different textures soils with or without organic fertilizers

A liberação do N em um solo sob adubação orgânica é afetada por vários fatores como a quantidade e as características do resíduo adicionado, as condições climáticas e o tipo de solo, dentre outros. Este estudo objetivou avaliar a eficiência da cama de aves de corte e do dejeto líquido de suínos em três solos de diferentes texturas. Foram incubados os solos franco-arenoso (238g argila kg-1), argilo-siltoso (470g argila kg-1) e muito-argiloso (605g argila kg-1), aos quais se adicionou ou não a cama de aves e o dejeto líquido de suínos. Foi determinada a progressão de N-NH4+ e N-NO3- aos 0, 7, 14, 28, 56 e 112 dias de incubação e calculou-se a taxa de mineralização líquida e as porcentagens de N disponível e de N mineral líquido em relação ao N total e orgânico adicionados, respectivamente. O maior teor de argila fez com que a nitrificação ocorresse de forma mais gradual, independente do tipo de adubo orgânico adicionado, o que contribui para diminuir o potencial poluente do N. A mineralização líquida do N também foi maior no solo franco-arenoso. Isso ratifica a recomendação de parcelar o suprimento do nitrogênio aos cultivos, em especial em solos arenosos e com dejetos líquidos ricos em N amoniacal. Os resultados sinalizam que os índices oficiais de eficiência de liberação do N (IELN), de 80% para o dejeto líquido de suínos e 50% para a cama de aves, podem estar superestimados. Nesse aspecto, parece ser importante descontar o N mineral liberado pelo solo no cálculo do IELN para não promover a depleção da matéria orgânica do solo a médio ou longo prazo. Por fim, os resultados apontam para a necessidade de aprofundar estudos para que as classes texturais dos solos sejam consideradas como uma variável para a recomendação de N através de adubos orgânicos.

The N release in the soil with organic fertilization is affected by various factors, such as the amount and the caractheristics of the added manure, climatic conditions and soil type. This study aimed to evaluate the effect of soil texture and the N release from two sources of organic fertilizer. Sandy loam soil (238mg clay kg-1), silt clay (470mg kg-1) and very-clay (605mg kg-1) were incubated, to which the poultry litter (47% N-NH4+) and the pig liquid slurry (14% N-NH4+) were added or not. The contents of N-NH4+ and N-NO3- was determined at 0, 7, 14, 28, 56 and 112 days after incubation and calculated the net mineralization and the percentage of available N and net mineral nitrogen in relation to the total and added organic N, respectively. The higher clay caused more gradually nitrification, regardless of the type of organic fertilizer added, which may helps to reduce the polluting potential of N. The net N mineralization was also higher in sandy loam soil. This confirms the recommendation to spread the supply of nitrogen to crops, particularly in sandy soils and slurry rich in N-ammonia. The results indicated that the official indices of efficiency of N release (IELN), of 80% for the pig liquid slurry and 50% for the poultry litter, may be overestimated. Therefore, it seems important to consider the N mineral of the soil in the calculation of the efficiency of the release to reduce the depletion of soil organic matter in a medium or long term. Finally, the results point to the need for further studies so that the soil texture classes are considered as a variable to the recommended nitrogen through organic fertilizers.

Polarization preserving ultra fast optical shutter for quantum information processing.

We present the realization of a ultra fast shutter for optical fields, which allows to preserve a generic polarization state, based on a self-stabilized interferometer. It exhibits high (or low) transmittivity when turned on (or inactive), while the fidelity of the polarization state is high. The shutter is realized through two beam displacing prisms and a longitudinal Pockels cell. This can represent a useful tool for controlling light-atom interfaces in quantum information processing.

Volatilização de amônia com aplicação de uréia na superfície do solo, no sistema plantio direto / Ammonia volatilization after urea surface applied in corn no-tillage

Com o objetivo de avaliar o efeito dos resíduos culturais de aveia preta (Avena strigosa), dispostos na superfície do solo, nas perdas de N por volatilização de amônia, conduziu-se um experimento a campo, em 2002/03, na UFSM (RS), em um Argissolo Vermelho distrófico arênico. O delineamento experimental foi o inteiramente casualizado, com três repetições. Os tratamentos constituíram da aplicação de uréia no milho, na presença e na ausência de resíduos culturais de aveia, em três épocas (pré-semeadura, semeadura e em cobertura). A uréia foi aplicada a lanço, sem incorporação ao solo, na dose equivalente a 50kg ha-1 de N, em cada época. Os resíduos culturais diminuíram os fluxos de volatilização de amônia quando eles proporcionaram maior umidade do solo no momento da aplicação da uréia, em relação ao solo descoberto. Em condições semelhantes de umidade de solo, entre os tratamentos com e sem resíduos culturais, houve maior volatilização de amônia, quando a uréia foi aplicada sobre os resíduos culturais. Quando ocorreu chuva no dia posterior a aplicação da uréia, não houve efeito dos resíduos culturais na volatilização de amônia. Na soma das três épocas de aplicação de uréia na cultura do milho, a quantidade de amônia volatilizada não diferiu entre os tratamentos com e sem resíduos culturais, com média de 17 por cento de perda do N-uréia aplicado.