Water and nitrogen footprint in an irrigated crop under mineral and organic fertilization

In order to establish rational nitrogen (N) application and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its balance is crucial. Excessive doses of N and/or water applied to fertigated crops involve a substantial risk of aquifer contamination by nitrate; but knowledge of N cycling and availability within the soil could assist in avoiding this excess. In central Spain, the main horticultural fertigated crop is the melon type ?piel de sapo¿ and it is cultivated in vulnerable zones to nitrate pollution (Directive 91/676/CEE). However, until few years ago there were not antecedents related to the optimization of nitrogen fertilization together with irrigation. Water and N footprint are indicators that allow assessing the impact generated by different agricultural practices, so they can be used to improve the management strategies in fertigated crop systems. The water footprint distinguishes between blue water (sources of water applied to the crop, like irrigation and precipitation), green water (water used by the crop and stored in the soil), and it is furthermore possible to quantify the impact of pollution by calculating the grey water, which is defined as the volume of polluted water created from the growing and production of crops. On the other hand, the N footprint considers green N (nitrogen consumed by the crops and stored in the soil), blue N (N available for crop, like N applied with mineral and/or organic fertilizers, N applied with irrigation water and N mineralized during the crop period), whereas grey N is the amount of N-NO3- washed from the soil to the aquifer. All these components are expressed as the ratio between the components of water or N footprint and the yield (m3 t-1 or kg N t-1 respectively). The objetives of this work were to evaluate the impact derivated from the use of different fertilizer practices in a melon crop using water and N footprint.

Respuesta fisiológica, productiva y cualitativa del cultivar Syrah (Vitis vinifera L) con diferentes frecuencias de riego y densidad de goteros en suelos arcillosos

La disponibilidad hídrica es uno de los principales factores que determinan el rendimiento del viñedo en muchas regiones vitícolas, por lo que sus consecuencias han sido ampliamente estudiadas. Sin embargo, para una cantidad de agua de riego determinada, otros aspectos como la frecuencia de aplicación, o la combinación entre el caudal de los goteros y la distancia entre los mismos (es decir, el patrón de distribución de agua en el suelo), pueden jugar un papel relevante, pero estos factores han sido poco estudiados. El objetivo de este trabajo ha sido evaluar las implicaciones agronómicas y fisiológicas de dos frecuencias de riego (IrrF, cada 2 y 4 días) y dos patrones de distribución de agua (DisP, goteros de 2 L h-1 separados 0,6 m vs. goteros de 4 L h-1 separados 1,2 m). El experimento se llevó a cabo durante cuatro temporadas consecutivas en un viñedo cv. Syrah con un suelo arcilloso en el centro de España, y los dos factores fueron evaluados bajo dos condiciones de disponibilidad hídrica (Baja: 20% de ETo y Media: 40% de ETo). El efecto de la frecuencia de riego y el patrón de distribución de agua en la respuesta agronómica del cv. Syrah se ha estudiado en el capítulo 1. La frecuencia de riego y el patrón de distribución de agua en el suelo afectaron a algunos aspectos de los componentes de rendimiento y desarrollo vegetativo en las dos condiciones de disponibilidad hídrica, aunque los efectos observados no fueron los mismos todos los años. Los efectos fueron más evidentes para IrrF en condiciones de baja disponibilidad hídrica y para DisP en condiciones de disponibilidad hídrica media. Dos de los cuatro años del experimento, el pasar de frecuencia de riego de 2 días a 4 días causó un incremento medio de rendimiento del 20% para la situación de baja disponibilidad hídrica. La textura del suelo, sin duda ha condicionado los resultados obtenidos en los tratamientos regados con el 20% de la ETo, ya que regar cada dos días implicaba la aplicación de pequeñas cantidades de agua y se formaban bulbos de riego superficiales, probablemente favoreciendo las pérdidas por evaporación. En el capítulo 2, se ha analizado el efecto de la frecuencia de riego y del patrón de distribución de agua en el estado hídrico de la planta y el intercambio gaseoso a nivel de hoja con el fin de explicar las diferencias observadas en la respuesta agronómica. En lo que respecta a la frecuencia de riego, en condiciones de baja disponibilidad hídrica, las plantas regadas cada 4 días (plantas 4d), mostraron mayores tasas de asimilación neta y conductancia estomática que las plantas regadas cada 2 días (plantas 2d), lo que es consistente con la hipótesis de que con la frecuencia de riego de 2 días se produjo una pérdida de eficiencia del uso del agua, probablemente debido a una mayor evaporación como consecuencia del hecho de que el volumen de suelo mojado creado era pequeño y cerca de la superficie. En condiciones de disponibilidad hídrica media, las diferencias en el intercambio gaseoso a nivel de hoja fueron mucho más pequeñas. Al comienzo del verano cada frecuencia de riego se comportó mejor uno de los días de medida, compensando al final del ciclo de riego de 4 días. Sin embargo, a medida que avanzó el verano y el déficit de agua se hizo más alto, las diferencias significativas aparecieron sólo en el 'día 4' del ciclo de riego, cuando las plantas 2d se comportaron mejor que las plantas regadas 4d que llevaban tres días sin regarse. Estas diferencias fisiológicas fueron menores que en condiciones de baja disponibilidad hídrica y al parecer no suficientes para afectar el comportamiento agronómico. En cuanto al patrón de distribución de agua, el efecto fue poco significativo, pero la mayor densidad de goteros tendió a presentar un mayor intercambio gaseoso a nivel de hoja, especialmente a media mañana. El efecto fue más importante para las condiciones de disponibilidad hídrica media. En el capítulo 3, se han comparado las relaciones entre el intercambio gaseoso a nivel de hoja, el estado hídrico y la demanda atmosférica, con el fin de explicar los cambios en la intensidad de la respuesta fisiológica observados en el Capítulo 2. No se han encontrado diferencias en dichas relaciones para el patrón de distribución de agua, por lo que sólo se ha analizado el efecto de la frecuencia de riego. El estudio se ha centrado fundamentalmente en si las plantas mostraron una respuesta fisiológica diferente a los cambios en el estado hídrico y en la demanda atmosférica según el tiempo transcurrido desde el último riego. Las diferencias observadas explican los resultados obtenidos en los capítulos anteriores, y sugieren la existencia de procesos de aclimatación vinculados a la frecuencia de riego y a la disponibilidad hídrica. Las plantas bajo condiciones de baja disponibilidad hídrica se mostraron más aclimatadas al estrés hídrico que aquellas en condiciones de disponibilidad hídrica media. La frecuencia de riego afectó claramente la relación entre los parámetros de intercambio gaseoso a nivel de hoja, el estado hídrico de la planta y las condiciones atmosféricas, y junto con la cantidad de agua aplicada tuvo implicaciones en el desarrollo de mecanismos de aclimatación que afectaron a la respuesta fisiológica de la planta, afectando a la eficiencia del riego. ABSTRACT Water availability is one of the major factors that determine vineyard performance in many grape growing regions, so its implications have been widely studied before. However, for a given irrigation water amount, other aspects such as application frequency, or emitter spacing and flow rate (i.e., distribution pattern), may play a relevant role, but these factors have been scarcely studied. The aim of this work was to evaluate the agronomic and physiological implications of two irrigation frequencies (IrrF, every 2 and 4 days) and two water distribution patterns (DisP, 2 L h−1 emitters every 0.6 m vs. 4 L h−1 emitters every 1.2 m). The experiment was carried out during four consecutive seasons in a cv. Syrah vineyard with a clay soil in central Spain, and the two factors were evaluated under two water availability conditions (LOW WA: 20% of ETo and MEDIUM WA: 40% of ETo). The effect of irrigation frequency and water distribution pattern on the agronomical response of cv. Syrah was studied in Chapter 1. IrrF and DisP affected some aspects of vegetative development and yield components under both water availability conditions, although the effects observed were not the same every year. The effects were more evident for IrrF under low water availability and for DisP under medium water availability. Two out of the four years of the experiment, the change of irrigation frequency from 2 days to 4 days promoted an average yield increase of 20% for the LOW WA situation. Soil texture certainly conditioned the results obtained under LOW WA conditions, since high frequency irrigation implied applying small amounts of water that resulted in limited superficial water bulbs, which probably favored water evaporation. In Chapter 2, the effect of irrigation frequency and water distribution pattern on plant water status and leaf gas exchange was analyzed to explain the differences observed in the agronomical response. Concerning irrigation frequency, under LOW WA conditions, applying irrigation every 4 days, resulted in higher net assimilation rates and stomatal conductance than doing it every 2 days, supporting the hypothesis that the latter frequency resulted in a water use efficiency loss, probably due to higher evaporation as a consequence of the fact the wetted soil volume created was small and close to the surface. Under MEDIUM WA conditions, differences in leaf gas exchange were much smaller. At the beginning of the summer each irrigation frequency behaved better one of the measurements days, compensating at the end of the 4-day irrigation cycle. However, as the summer progressed and water deficit became higher, significant differences appeared only on ‘day 4’ of the irrigation cycle, when 2d plants behaved better than 4d plants. These physiological differences were smaller than under LOW WA conditions and apparently not sufficient to affect agronomical performance. Regarding water distribution pattern, the effect was less significant but the closest emitter spacing resulted in general terms in a higher leaf gas exchange, especially at midmorning. The effect was more noticeable for MEDIUM WA conditions. In Chapter 3, the relationships between leaf gas exchange and leaf water status and atmospheric demand were compared to explain the changes in the intensity of the physiological response observed in Chapter 2. No differences were found in the relationships for water distribution pattern, so only the effect of irrigation frequency was analyzed focusing on whether the plants have a different physiological response to changes in water status and atmospheric demand according to the time elapsed since the last irrigation. Differences observed in the relationships explained the results obtained in the previous chapters, and point at the occurrence of acclimation processes linked to irrigation frequency and to water availability. Plants under LOW WATER AVAILABILITY conditions seemed to be more acclimated to water stress than those under MEDIUM WATER AVAILABILITY conditions. Irrigation frequency clearly affected the relationship between leaf gas exchange parameters, plant water status and atmospheric conditions, and together with the amount of water applied had implications in the development of acclimation mechanisms that affected plant physiological response, thus affecting irrigation efficiency.

Evaluación de Ulmus pumila L. y Populus spp. como cultivos energéticos en corta rotación

El presente trabajo estudia el empleo del olmo de Siberia (Ulmus Pumila L.) y el chopo (Populus spp.) en corta rotación y alta densidad para la producción de biomasa con fines energéticos. En el área mediterránea las disponibilidades hídricas son limitadas, por lo que la mayoría de los cultivos energéticos utilizados hasta el momento requieren el aporte de agua de riego; por ello resulta fundamental encontrar especies con bajos requerimientos hídricos, analizar la eficiencia en el uso del agua de diferentes materiales genéticos y optimizar la dosis de riego. Las parcelas experimentales se ubicaron en la provincia de Soria. En el ensayo llevado a cabo con olmo de Siberia se ha analizado el efecto en la producción de la disponibilidad de agua mediante el establecimiento de parcelas en secano y con dos dosis de riego (2000 m3 ha-1 año-1 y 4000 m3 ha-1 año-1 aproximadamente); además, al ser una especie poco estudiada hasta el momento, se ha estudiado también el efecto que tiene sobre el rendimiento la densidad de plantación (3.333 plantas ha-1 y 6.666 plantas ha-1), el tipo de suelo (2 calidades diferentes) y el turno de corta (3 y 4 años). En el caso del chopo, se han evaluado cuatro clones (AF-2, I-214, Monviso y Pegaso) establecidos con una densidad de 20.000 plantas por hectárea. Durante el primer ciclo de tres años se aportó el mismo volumen de riego a todas las parcelas, mientras que durante el segundo ciclo se establecieron 8 regímenes hídricos diferentes. Por otra parte, se ha investigado sobre el uso del potencial hídrico de las plantas para evaluar el estrés hídrico de las mismas y se ha estimado la producción de biomasa foliar y el Índice de Área Foliar (LAI) de ambas especies, relacionando los valores obtenidos con la dosis de riego y la producción de biomasa. Los resultados muestran que los suelos inundados reducen la tasa de supervivencia de los olmos durante el periodo de implantación, sin embargo la mortalidad durante los siguientes periodos vegetativos es baja y muestra buena capacidad de rebrote. La productividad (kg ha-1 año-1) obtenida fue mayor con un turno de corta de cuatro años que con turno de tres años. El área basal y la altura fueron variables eficaces para predecir la producción de biomasa del olmo de Siberia, obteniendo una variabilidad explicada de más del 80%. En cuanto a los parámetros que mayor influencia tuvieron sobre el crecimiento, el tipo de suelo resulto ser el más relevante, obteniéndose en un suelo agrícola considerado de buena calidad una producción en condiciones de secano de unos 8.000 kg ha-1 año-1. En condiciones de regadío el rendimiento del olmo de Siberia fue al menos el doble que en secano, pero la diferencia entre las dos dosis de riego estudiadas fue pequeña. La producción de biomasa fue mayor en la densidad de plantación más alta (6.666 plantas ha–1) en las parcelas de regadío, sin embargo no se encontraron diferencias significativas entre las dos densidades en secano. El clon de chopo que presentó un mayor rendimiento durante el primer ciclo fue AF-2, alcanzando los 14.000 kg ha-1 año-1, sin embargo la producción de este clon bajó sustancialmente durante el segundo ciclo debido a su mala capacidad de rebrote, pasando a ser I-214 el clon más productivo llegando también a los 14.000 kg ha-1 año-1. Un aporte adicional de agua proporcionó un incremento de la biomasa recogida, pero a partir de unos 6.500 m3 ha-1 año-1 de agua la producción se mantiene constante. El potencial hídrico foliar ha resultado ser una herramienta útil para conocer el estrés hídrico de las plantas. Los olmos de regadío apenas sufrieron estrés hídrico, mientras que los implantados en condiciones de secano padecieron un acusado estrés durante buena parte del periodo vegetativo, que se acentuó en la parte final del mismo. Los chopos regados con las dosis más altas no sufrieron estrés hídrico o fue muy pequeño, en las dosis intermedias sufrieron un estrés moderado ocasionalmente y únicamente en las dosis más bajas sufrieron puntualmente un estrés severo. El LAI aumenta con la edad de los brotes y oscila entre 2 y 4 m2 m−2 en los chopos y entre 2 y 7 m2 m−2 en los olmos. Se encontró una buena relación entre este índice y la producción de biomasa del olmo de Siberia. En general, puede decirse que el olmo de Siberia podría ser una buena alternativa para producir biomasa leñosa en condiciones de secano, mientras que el chopo podría emplearse en regadío siempre que se haga una buena elección del clon y de la dosis de riego. ABSTRACT This work explores the possibilities of biomass production, for energy purposes, of Siberian elm (Ulmus Pumila L.) and poplar (Populus spp.) in Spain. Irrigation is required for the viable cultivation of many energy crops in Mediterranean areas because of low water availability, for this reason species with low water requirements should be a good alternative for biomass production. Moreover, the optimal amount of irrigation water and the performance of the different genetic material in terms of production and water use efficiency should be studied in order to use water wisely. The experimental plots were established in the province of Soria in Spain. Given the small amount of information available about Siberian elm, besides studying the influence of water availability (rain-fed and two different irrigation doses) on biomass production, two different plantation densities (3,333 plants ha-1 and 6,666 plants ha-1), two different soil type and two cutting cycles (three years and four years) were assessed. In the case of poplar, four clones belonging to different hybrids (I-214, AF2, Pegaso, and Monviso) were included in a high density plantation (20,000 plants ha-1). During the first cycle, the water supplied in all plots was the same, while 8 different watering regimes were used during the second cycle. The suitability of the use of the leaf water potential to assess the water stress situations has also been investigated. Moreover, leaf biomass production and leaf area index (LAI) were estimated in both species in order to analyze the relationship between these parameters, irrigation dose and biomass production. The results shows that flooded soils have an adverse effect on elm survival in the implantation period, but the percentage of mortality is very low during the following vegetative periods and it shows a good ability of regrowth. The annual yield from a four-year cutting cycle was significantly greater than that from the three-year cutting cycle. Basal diameter and height are effective variables for predicting the production of total biomass; equations with R squared higher than 80% were obtained. The analysis of parameters having an influence on elm growth shows that soil type is the most important factor to obtain a good yield. In soils with enough nutrients and higher waterholding capacity, biomass productions of 8,000 kg ha-1 yr-1 were achieved even under rain-fed conditions. In irrigated plots, Siberian elm production was double than the production of biomass under rain-fed conditions; however, small differences were obtained between the 2 different irrigation doses under study. Biomass yield was greater for the highest planting density (6,666 plants ha–1) in irrigated plots, but significant differences were not found between the 2 densities in rain-fed plots. The clone AF-2 showed the highest production (14,000 kg ha-1 yr-1) during the first cycle, however during the second cycle its growth was lower because of a high mortality rate after regrowth and I-214 achieves the greatest production (14,000 kg ha-1 yr-1). An additional water supply provided a greater amount of biomass, but over about 6500 m3 ha-1 yr-1 of water the production is constant. Leaf water potential has been shown to be a useful tool for finding out plant water status. Irrigated elms hardly suffered water stress, while rain-fed elms suffered a pronounced water stress, which was more marked at the end of the vegetative period. Most of poplars did not show water stress; leaf water potentials only showed an important water stress in the plots irrigated with the lowest doses. LAI increases with shoot age and it ranges from 2 to 4 m2 m−2 in poplars and from 2 to 7 m2 m−2 in elms. A good relationship has been found between this index and Siberian elm production. In general, Siberian elm could be a good alternative to produce woody biomass in rainfed plots, while poplar could be used in irrigated plots if a suitable clone and irrigation dose are chosen.

Estimating the Excess Investment in Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase in Leaves of Spring Wheat Grown under Elevated CO21

Wheat (Triticum aestivum L.) was grown under CO2 partial pressures of 36 and 70 Pa with two N-application regimes. Responses of photosynthesis to varying CO2 partial pressure were fitted to estimate the maximal carboxylation rate and the nonphotorespiratory respiration rate in flag and preceding leaves. The maximal carboxylation rate was proportional to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content, and the light-saturated photosynthetic rate at 70 Pa CO2 was proportional to the thylakoid ATP-synthase content. Potential photosynthetic rates at 70 Pa CO2 were calculated and compared with the observed values to estimate excess investment in Rubisco. The excess was greater in leaves grown with high N application than in those grown with low N application and declined as the leaves senesced. The fraction of Rubisco that was estimated to be in excess was strongly dependent on leaf N content, increasing from approximately 5% in leaves with 1 g N m−2 to approximately 40% in leaves with 2 g N m−2. Growth at elevated CO2 usually decreased the excess somewhat but only as a consequence of a general reduction in leaf N, since relationships between the amount of components and N content were unaffected by CO2. We conclude that there is scope for improving the N-use efficiency of C3 crop species under elevated CO2 conditions.

Acurácia da seleção simultânea para caracteres de interesse em milho tropical de segunda safra

O milho de segunda safra, também conhecido como milho safrinha, é definido como aquele semeado entre os meses de janeiro e março. Esta modalidade de cultivo atingiu no ano agrícola de 2013/2014 uma área plantada de 9,18 milhões de hectares, superior a área cultivada com milho primeira safra, que no mesmo período foi de 6,61 milhões de hectares. Na segunda safra, há alto risco de instabilidades climáticas, principalmente em decorrência de baixas temperaturas, geadas, má distribuição de chuvas e redução do fotoperíodo. Todos estes fatores prejudicam a atividade fotossintética do milho, reduzindo sua produtividade. No entanto, dada a importância deste cultivo, empresas públicas, privadas e universidades vêm buscando incrementar a produtividade e a estabilidade. Para isso, alguns caracteres são especialmente preconizados. Devido ao alto risco de perda por adversidades ambientais, muitos produtores investem pouco em adubação, principalmente adubação nitrogenada. Neste contexto, o desenvolvimento de plantas mais eficientes no uso e, ou, tolerantes ao estresse por nitrogênio, resultaria em maior segurança para o produtor. Não obstante, a precocidade tem elevada importância, já que materiais precoces reduzem o risco de perdas neste período. No entanto, a mesma deve estar sempre associada a alta produtividade. Assim, para a seleção simultânea destes caracteres, pode-se lançar mão de índices per se de resposta das plantas ao estresse, análises gráficas e, ou, índices de seleção simultânea. Adicionalmente, os valores genotípicos das linhagens para essas características, além de serem preditos via REML/BLUP single-trait (análise univariada), também podem ser preditos via REML/BLUP multi-trait (análise multivariada). Dessa forma, os valores genotípicos são corrigidos pela covariância existente entre os caracteres. Assim, o objetivo deste trabalho foi verificar a possibilidade de seleção simultânea para eficiência no uso e tolerância ao estresse por nitrogênio, além de plantas precoces e produtivas. Para isto, linhagens de milho tropical foram cultivadas e avaliadas para estes caracteres. Foram então simulados diversos cenários de seleção simultânea. A partir destes resultados, observou-se que o índice per se de resposta das plantas ao estresse Média Harmônica da Performance Relativa (MHPR) foi o mais eficiente na seleção de plantas eficientes no uso e tolerantes ao estresse por nitrogênio. Isto ocorreu devido a forte correlação desfavorável entre os índices que estimam a eficiência e a tolerância, além da superioridade e em acurácia, herdabilidade e ganhos com a seleção deste índice per se. Já para a seleção simultânea da produtividade e precocidade, o índice Aditivo de seleção simultânea, utilizando os valores genotípicos preditos via REML/BLUP single-trait se mostrou o mais eficiente, já que obteve ganhos satisfatórios em todos os caracteres e há a possibilidade de modular, de forma mais satisfatória, os ganhos em cada caractere. Conclui-se que a seleção simultânea tanto para eficiência no uso e tolerância ao estresse por nitrogênio, quanto para produtividade e precocidade são possíveis. Além disso, a escolha do melhor método de seleção simultânea depende da magnitude e do sentido da correlação entre os caracteres.

Eficiência de uso de nitrogênio pela cana-de-açúcar: diferenças genotípicas, preferência por amônio e emissão de N2O

O uso ineficiente do nitrogênio (N) é um problema global, que pode diminuir a sustentabilidade da produção agrícola da cana-de-açúcar para fins energéticos devido às emissões de N2O oriundas da fertilização nitrogenada. A eficiência de utilização de nitrogênio (EUN) tem sido pouco estudada em genótipos de cana-de-açúcar, o que pode ser preocupante devido a importância da cultura para o país. O objetivo desse estudo foi avaliar a EUN de genótipos de cana-de-açúcar, verificando se genótipos contrastantes tem preferência de absorção por amônio ao invés de nitrato, e checar se extratos radiculares de Brachiaria humidicola e Saccharum spontaneum aumentam a eficiência de utilização de N pela cultura. Para isso três experimentos foram desenvolvidos em condições controladas em casa-de-vegetação e câmara de crescimento. No primeiro deles, 18 genótipos foram submetidos a dois níveis de N: limitante (baixo N) e suficiente (alto N). Posteriormente, quatro genótipos selecionados quanto a EUN do primeiro experimento, foram cultivados em câmara de crescimento por 69 dias, onde receberam quantidades conhecidas de N-fertilizante marcado ou no 15NH4+ ou no 15NO3-, sendo avaliados 24 e 72 horas após a aplicação do fertilizante marcado. Um terceiro ensaio foi realizado, em que extratos radiculares de Brachiaria humidicola (BCH) e Saccharum spontaneum (SCS) foram aplicados ao solo com o intuito de verificar seu potencial como inibidor da nitrificação, comparando-os com a dicianodiamida (DCD), e seu efeito para o aumento do aproveitamento do N pela cana-de-açúcar. No experimento de EUN verificou-se grande variação entre os genótipos. Dos 18 genótipos avaliados, seis foram classificados como responsivos a N e eficientes na utilização de N, três foram não eficientes e responsivos; dois foram eficientes e não responsivos, e sete não eficientes e não responsivos. Esse resultado comprova que a recomendação da adubação nitrogenada pode realmente estar pouco precisa, pois não leva em consideração a EUN de cada genótipo, sendo realizada uma aplicação genérica. As medições de fotossíntese mostraram que os genótipos mais eficientes na utilização do N, não necessariamente possuem as taxas fotossintéticas mais elevadas, estando a EUN diretamente relacionada à quantidade de raízes das plantas. No segundo trabalho, verificou-se que o N na planta proveniente do fertilizante (NPPF), 72 horas após a aplicação do N, foi 36% menor quando a fonte marcada foi NO3-, atestando que a cana-de-açúcar tem preferência de absorção por amônio em relação ao nitrato nos primeiros dias após a adubação nitrogenada. Por fim, os resultados do terceiro ensaio mostraram que a aplicação de sulfato de amônio (SA), associado ao inibidor sintético DCD, manteve os valores de N-NO3- baixos ao longo de todo período de avaliação (durante 60 dias), enquanto que com SA, SA+BCH e SA+SCS houve um aumento na concentração de nitrato no solo já a partir de 15 dia após a fertilização. O uso de DCD reduziu o fluxo médio de N2O durante o período de avaliação em relação ao uso isolado do fertilizante, o que não foi observado com o uso de extratos de raízes de Brachiaria humidicola e Saccharum spontaneum

Primary and secondary metabolites production in signal grass around the year under nitrogen fertilizer

Plants produce a number of substances and products and primary and secondary metabolites (SM) are amongst them with many benefits but limitation as well. Usually, the fodder are not considered toxic to animals or as a source having higher SM. The Brachiaria decumbens has a considerable nutritional value, but it is considered as a toxic grass for causing photosensitization in animals, if the grass is not harvested for more than 30 days or solely. The absence of detailed information in the literature about SM in Brachiaria, metabolites production and its chemical profile enable us to focus not only on the nutritive value but to get answers in all aspects and especially on toxicity. The study was conducted in the period of december 2013 to december 2014; in greenhouse FZEA-USP. B. decumbens was used with two cutting heights (10 and 20 cm) and nitrogen doses (0, 150, 300 and 450 kg ha-1) in complete randomized block design. The bromatological analysis were carried out on near infrared spectroscopy. Generally, the application of 150 kg ha-1 N was sufficient to promote the nutritional value in B. decumbens but above it the nitrogen use efficiency decline significantly. The highest dry matter yield (99.97 g/pot) was observed in autumn and the lowest was in winter (30.20 g/pot). While, as per nitrogen dose the average highest dry matter yield was at 150 kg ha-1 (79.98 g/pot). The highest crude protein was observed in winter (11.88%) and the lowest in autumn (7.78%). By the cutting heights; the 10 cm proved to have high CP (9.51%). In respect of fibrous contents, the highest acid detergent fiber was noted in summer (36.37%) and lowest in winter (30.88%). While the neutral detergent fiber was being highest in autumn and lowest in spring (79.60%). The highest in vitro dry matter and organic matter digestibilities were noted at 300 kg ha-1 N; being 68.06 and 60.57%; respectively; with the lowest observed in without N treatments (62.63% and 57.97), respectively. For determination of the classes, types and concentration of SM in B. decumbens, phytochemical tests, thin layer and liquid chromatography-mass spectrometry and nuclear magnetic resonance analysis were carried out. Height, nitrogen and seasons significantly (P <0.0001) affected the secondary metabolic profile. A new protodioscin isomer (protoneodioscin (25S-)) was identified for first time in B. decumbens and is supposed to be the probable toxicity reason. Its structure was verified by 1D and 2D NMR techniques (1H, 13C) and 1D (COSY-45, edited HSQC, HMBC, H2BC, HSQC -TOCSY, NOESY and 1 H, 1 H, J). All factors influence the metabolic profile significantly (P <0.0001). The lowest phenols were at 300 kg ha-1 while the lowest flavones were at 0 kg ha-1. Season wise the highest phenols occurred in autumn (19.65 mg/g d.wt.) and highest flavones (28.87 mg/g d.wt.) in spring. Seasons effect the saponin production significantly (P <0.0001) and the results showed significant differences in the protodioscin (17.63±4.3 - 22.57±2.2 mg/g d.wt.) and protoneodioscin (23.3±1.2 - 31.07±2.9 mg/g d.wt.) concentrations. The highest protodioscin isomers concentrations were observed in winter and spring and by N doses the highest were noted in 300 kg ha-1. Simply, all factors significantly played their role in varying concentrations of secondary metabolites.

Processes for identifying regional influences of and responses to increasing atmospheric CO2 and climate change : the MINK project /

"TR052A-H."

An interview-based cognitive analysis of stakeholder perceptions of whale watching in Puget Sound, Washington

Thesis (Master's)--University of Washington, 2016-06

General practitioners' role in preventive medicine: scenario analysis using alcohol as a case study

The purpose of this analysis is threefold: first, to extract from the literature, current levels of GP detection of at-risk drinking by their patients, rates at which general practitioners (GPs) offer an intervention; and the effectiveness of these interventions; secondly, to develop a model based on this literature to be used in conjunction with scenario analysis; and thirdly, to consider the cost implications of current efforts and various scenarios. This study deals specifically with Australian general practice. A two-step procedure is used in the scenario analysis, which involves identifying opportunities for detection, intervention, effectiveness and assigning probabilities to outcomes. The results suggest that increasing rates of GP intervention achieves greatest benefit and return on resource use. For every 5% point increase in the rate of GP intervention, an additional 26 754 at-risk drinkers modify their drinking behaviour at a cost of $231.45 per patient. This compares with a cost per patient modifying drinking behaviour of $232.60 and $208.31 for every 5% point increase in the rates of detection and effectiveness, respectively. The knowledge, skill and attitude of practitioners toward drinking are significant, and they can be the prime motivators in persuading their patients to modify drinking behaviour.

A cost-effectiveness analysis of buprenorphine-assisted heroin withdrawal

The purpose of this study was to conduct a cost - effectiveness analysis of detoxification from heroin using buprenorphine in a specialist clinic versus a shared care setting. A randomized controlled trial was conducted with a total of 115 heroin-dependent patients receiving a 5-day treatment regime of buprenorphine. The specialist clinic was a community-based treatment agency in inner-city Sydney. Shared care involved treatment by a general practitioner supplemented by weekend dispensing and some concurrent counselling at the specialist clinic. Quanti. cation of resource use was limited to inputs for treatment provision. The primary outcome measure used in the economic analysis was the proportion of each group that completed detoxification and achieved an initial 7-day period of abstinence. Buprenorphine detoxification in the shared care setting was estimated to be $24 more expensive per patient than treatment at the clinic, which had an average treatment cost of $332 per patient. Twenty-three per cent of the shared care patients and 22% of the clinic patients reported no opiate use during the withdrawal period. These results suggest that the provision of buprenorphine treatment for heroin dependence in shared care and clinic appear to be equally cost - effective.

A simulation model of cereal-legume intercropping systems for semi-arid regions I. Model development

Cereal-legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index (K-T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients (K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods x 3 factors). The model calibration and validation were carried out with maize-bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997-2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal-legume intercrop models for semi-arid regions. (c) 2004 Elsevier B.V. All rights reserved.

Rice morphogenesis and plant architecture: Measurement, specification and the reconstruction of structural development by 3D architectural modelling

Background and Aims The morphogenesis and architecture of a rice plant, Oryza sativa, are critical factors in the yield equation, but they are not well studied because of the lack of appropriate tools for 3D measurement. The architecture of rice plants is characterized by a large number of tillers and leaves. The aims of this study were to specify rice plant architecture and to find appropriate functions to represent the 3D growth across all growth stages. Methods A japonica type rice, 'Namaga', was grown in pots under outdoor conditions. A 3D digitizer was used to measure the rice plant structure at intervals from the young seedling stage to maturity. The L-system formalism was applied to create '3D virtual rice' plants, incorporating models of phenological development and leaf emergence period as a function of temperature and photoperiod, which were used to determine the timing of tiller emergence. Key Results The relationships between the nodal positions and leaf lengths, leaf angles and tiller angles were analysed and used to determine growth functions for the models. The '3D virtual rice' reproduces the structural development of isolated plants and provides a good estimation of the fillering process, and of the accumulation of leaves. Conclusions The results indicated that the '3D virtual rice' has a possibility to demonstrate the differences in the structure and development between cultivars and under different environmental conditions. Future work, necessary to reflect both cultivar and environmental effects on the model performance, and to link with physiological models, is proposed in the discussion.

Links between tree species, symbiotic fungal diversity and ecosystem functioning in simplified tropical ecosystems

We studied the relationships among plant and arbuscular mycorrhizal (AM) fungal diversity, and their effects on ecosystem function, in a series of replicate tropical forestry plots in the La Selva Biological Station, Costa Rica. Forestry plots were 12 yr old and were either monocultures of three tree species, or polycultures of the tree species with two additional understory species. Relationships among the AM fungal spore community, host species, plant community diversity and ecosystem phosphorus-use efficiency (PUE) and net primary productivity (NPP) were assessed. Analysis of the relative abundance of AM fungal spores found that host tree species had a significant effect on the AM fungal community, as did host plant community diversity (monocultures vs polycultures). The Shannon diversity index of the AM fungal spore community differed significantly among the three host tree species, but was not significantly different between monoculture and polyculture plots. Over all the plots, significant positive relationships were found between AM fungal diversity and ecosystem NPP, and between AM fungal community evenness and PUE. Relative abundance of two of the dominant AM fungal species also showed significant correlations with NPP and PUE. We conclude that the AM fungal community composition in tropical forests is sensitive to host species, and provide evidence supporting the hypothesis that the diversity of AM fungi in tropical forests and ecosystem NPP covaries.

Effect of nitrogen supply on leaf appearance, leaf growth, leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N-a (g m(-2) N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84-6.0 g N pot(-1)) and five rates (0.5-6.0 g pot(-1)) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P a,, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N-a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P-max and N-a. The results confirm the 'maize strategy': leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the 'potato strategy' can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the 'maize strategy' for adaptation to N limitation. (c) 2004 Elsevier B.V. All rights reserved.