30,734 research outputs found

    Efeitos dos nanomateriais no microbioma do solo: aplicação de nano-agroquímicos e biosólidos

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    The frequent application of agrochemicals and/or biosolids in agriculture may lead to an increased concentration and persistence of nanomaterials (NMs) in agricultural soils. Some of these NMs are characterized by their antimicrobial properties, affecting the microbial communities in soil, which are essential in maintaining ecosystem‚Äôs function and balance. A negative impact of these NMs on soil quality, fertility and biogeochemical processes could result in economic losses to the agricultural sector. Thus, the main aim of this thesis was to evaluate the effect of NMs on the soil microbiome and demonstrate the potential of several microbiological endpoints for the risk assessment of these NMs. For this, several NMs were tested, under different exposure scenarios, with copper-based formulations: the commercial nanopesticide Kocide¬ģ3000, copper oxide nanoparticles (nCuO) and copper hydroxide nanoparticles [nCu(OH)2]; and a silver sulfide nanoparticle (Ag2S NPs), simulating aging of AgNPs. In these experiments, the presence and/or absence of edaphic elements (invertebrates and plants), essential to the maintenance of soil functioning, was considered. Crosswise, the soil microbiome was evaluated at the structural, compositional (Denaturing Gradient Gel Electrophoresis and massive parallel sequencing), and functional levels (soil enzymatic activity, community-level physiological profiling and abundance of bacterial groups using culture-dependent methods and/or qPCR technique). Particularly for copper-based NMs, a long exposure to the commercial nanopesticide (90 days) in microcosms, using recommended concentrations for vineyard areas, influenced the structure/richness of the soil bacterial and fungal communities and the regulation of the carbon cycle. With the inclusion of decomposer organisms (Porcellionides pruinosus), these differences were not observed, suggesting an attenuated effect of this nanopesticide on the soil microbiome. Simulating more realistic conditions, the application of different copper-based NMs in mesocosms (in the presence of plants and invertebrates), resulted in a reduced abundance of bacterial classes involved in the regulation of soil organic matter and in the nitrogen cycle (depending on the tested formulation), and enzymatic activities associated with the sulfur, carbon and nitrogen cycles, after 28 days of exposure. Also, an earlier effect of these NMs in the rhizosphere microbiome (14 days) was detected compared to the effect on the non-rhizosphere soil microbiome, suggesting a faster dissolution of these NMs resulting from the root exudates activity. Regarding silver NMs, the results suggest that the exposure to Ag2S NPs affect the soil microbiome involved in the regulation of the carbon cycle (reduced ő≤-glucosidase activity, and increased abundance of bacterial classes involved in the degradation of cellulose). The function prediction analysis revealed that silver exposure changes the functioning of the nitrification process. It was also verified the emergence of variants of genes amoA and nxrB in silver-treated soils, suggesting the replacement of bacterial groups that comprise these genes. Finally, this work highlights the relevance of including the soil microbiome as an essential endpoint in the risk assessment of NMs, using a more realistic exposure scenario, for a deeper understanding of the impact of these compounds on the terrestrial environment. This work also highlights the need for specific regulation in the risk assessment of these compounds in the environment.A aplica√ß√£o frequente de agroqu√≠micos e/ou de bios√≥lidos na agricultura poder√° levar a um aumento acentuado da concentra√ß√£o, bem como a poss√≠vel persist√™ncia de nanomateriais (NMs) em solos agr√≠colas. Alguns destes NMs s√£o caracterizados pelas suas propriedades antimicrobianas, podendo afetar as comunidades microbianas do solo, essenciais na manuten√ß√£o da fun√ß√£o e equil√≠brio do ecossistema. Um impacto negativo na qualidade, na fertilidade e nos processos biogeoqu√≠micos do solo, poder√° resultar em perdas econ√≥micas no sector agr√≠cola. Assim, o objetivo principal desta tese consistiu em avaliar o efeito de NMs no microbioma do solo, e demonstrar a potencialidade dos par√Ęmetros microbiol√≥gicos na avalia√ß√£o do risco ambiental destes NMs. Para isso, foram testados, sob diferentes cen√°rios de exposi√ß√£o, v√°rios NMs com formula√ß√Ķes √† base de cobre: o nanopesticida comercial Kocide¬ģ3000, nanopart√≠culas de √≥xido de cobre (nCuO) e nanopart√≠culas de hidr√≥xido de cobre [nCu(OH)2], e √† base de prata, com nanopart√≠culas de prata sulfatada (Ag2S NPs). Nestes cen√°rios, a presen√ßa e/ou aus√™ncia de elementos ed√°ficos (invertebrados e plantas) essenciais √† manuten√ß√£o do funcionamento do solo, foram consideradas. Transversalmente, o microbioma do solo foi avaliado ao n√≠vel estrutural e composicional (Eletroforese em Gel de Gradiente Desnaturante e sequencia√ß√£o massiva paralela) e funcional (atividade enzim√°tica do solo, perfil fisiol√≥gico da comunidade e abund√Ęncia de grupos bacterianos por m√©todos cultiv√°veis e/ou qPCR). Particularmente para os NMs √† base de cobre, uma exposi√ß√£o longa do nanopesticida comercial (90 dias), em microcosmos e com concentra√ß√Ķes recomendadas para √°reas vit√≠colas, influenciou a estrutura/riqueza da comunidade bacteriana e f√ļngica do solo e a regula√ß√£o do ciclo de carbono. Com a inclus√£o de organismos decompositores (Porcellionides pruinosus) neste ensaio, estas diferen√ßas n√£o foram observadas, sugerindo uma atenua√ß√£o do efeito deste nanopesticida no microbioma do solo. Aquando da simula√ß√£o de condi√ß√Ķes mais realistas, a aplica√ß√£o de diferentes NMs √† base de cobre em mesocosmos (na presen√ßa de invertebrados e plantas), resultou na redu√ß√£o da abund√Ęncia de classes bacterianas envolvidas na regula√ß√£o da mat√©ria org√Ęnica do solo (dependendo da formula√ß√£o testada), e atividades enzim√°ticas associadas aos ciclos de enxofre, carbono e azoto, ap√≥s 28 dias de exposi√ß√£o. Foi tamb√©m detetado um efeito mais r√°pido destes NMs no microbioma da rizosfera (14 dias) quando comparado com o efeito no microbioma do solo n√£o rizosf√©rico, sugerindo uma dissolu√ß√£o mais r√°pida destes NMs devido √† a√ß√£o dos exsudados radiculares. Relativamente aos NMs de prata, os resultados sugerem que a exposi√ß√£o da prata sulfatada afeta o microbioma do solo principalmente ao n√≠vel da regula√ß√£o do ciclo do carbono (redu√ß√£o da atividade da ő≤-glucosidase, e o aumento da abund√Ęncia de classes bacterianas envolvidas na degrada√ß√£o da celulose). Ap√≥s an√°lise de previs√£o de fun√ß√£o, a exposi√ß√£o a prata alterou o funcionamento do processo de nitrifica√ß√£o. Verificou-se tamb√©m o aparecimento de variantes dos genes amoA e nxrB nos solos contaminados, sugerindo assim a substitui√ß√£o de grupos bacterianos que apresentam estes genes. Por fim, este trabalho evidencia a relev√Ęncia da inclus√£o do microbioma do solo como um par√Ęmetro essencial na avalia√ß√£o de risco dos NMs, sob cen√°rios de exposi√ß√£o mais realistas, para uma compreens√£o mais profunda do impacto destes compostos no ambiente terrestre. Evidencia tamb√©m a necessidade da implementa√ß√£o de legisla√ß√£o espec√≠fica para a avalia√ß√£o de risco ambiental destes compostos.Programa Doutoral em Biologia e Ecologia das Altera√ß√Ķes Globai

    Understanding Zea mays genetic influence on the structure and function of the rhizosphere microbiome

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    Assembly of the plant rhizosphere microbiome is driven by plant genetic and evolutionary history. Plant microbiomes play a major role in altering plant resilience, fitness, nutrition, and productivity. Plant hosts selectively filter microorganisms that colonize their rhizosphere. This selective process is heritable across plant cultivars, yet the implication of heritability on rhizosphere microbiome function has been relatively unexplored. This dissertation attempts to characterize the N-cycling functions associated with heritable recruitment to the rhizosphere microbiome. The following dissertation aims to address these specific objectives: examine whether the contemporary agricultural practices that maize has experienced over the past 50 years of breeding has altered the rhizosphere N-cycling microbiome assembly, determine how domestication altered modern maize rhizosphere microbiome assembly from its ancestral progenitor teosinte, assess whether these genotype driven microbiome assembly processes persist in the field setting and influence N-cycling ecosystem function and finally attempt to determine the underlying genetic regions and mechanisms contributing to differential microbial community assembly and function in the rhizosphere. The findings of these specific objectives suggest that the maize microbiome has been unintentionally altered through the process of contemporary breeding and domestication, resulting in the microbiome interaction to be less agriculturally sustainable. These anthropogenic driven changes to the maize microbiome can be characterized by changes in nitrifying and denitrifying microbiome recruitment that consequently alter the rates of nitrification and denitrification of a soil. Furthermore, wild genetic diversity appears to house more sustainable N-cycling microbiome interactions compared to modern maize. The dissertation closes by showing how ‚Äúrewilding‚ÄĚ the plant microbiome interaction could be a potential solution to improve our agricultural system. Modern agricultural practices have resulted in the unprecedented degradation of our global nitrogen cycle. This N-cycle disruption by agriculture has been primarily driven by the over-application of synthetic N fertilizers. On average only about half of this applied synthetic N is taken up by our focal crop, while the remainder is lost through microbiome activities such as nitrification and denitrification. Broadly, the work in this dissertation shows that genotype-driven rhizosphere microbiome assembly can have a considerable effect on N-cycling functional groups that carry out nitrification and denitrification. Additionally, this dissertation suggests that at least in maize, a global staple crop, it appears that breeding has disrupted N-cycling functional group control in the rhizosphere especially when compared to its wild progenitor teosinte. Finally, we show that modern maize can regain the ability to influence N-cycling microbes in the rhizosphere with genetic introgressions from teosinte. Overall, this dissertation uses a combination of microbial ecology and plant genetics to provide some explanations for why our contemporary agricultural system is so unsustainable (via N-pollution) and provides some potential solutions to improve it (via rewilding).U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste

    Effects of Cropping Systems on Soil Physicochemical Properties and Abundances and Spatial Distributions of Nitrogen-Cycling Bacteria

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    Soil nitrogen (N) is a common limiting factor where soil N-cycling is a key component of agroecosystems. Soil N transformation processes are largely mediated by microbes, and understanding bacteria involvement in soil N-cycling in agricultural systems has both agronomic and environmental importance. This 2 yr field-scale study examined the abundances and spatial distributions of the total bacterial community (16S rRNA), bacteria involved in nitrification (amoA) and denitrification (narG, nirK, and nosZ), and soil physicochemical properties of winter wheat (Triticum aestivum L.)‚Äďsoybean (Glycine max L.) double-crop with 2‚Äď3 weeks of spring grazing (WGS) and without grazing (WS) and tall fescue (Festuca arundinacea (L.) Schreb.) pasture (TF) managed to near-natural conditions with similar grazing. The TF soil had a significantly higher abundance of 16S rRNA, amoA, narG, nirK, and nosZ genes than the WS and WGS soils, which had similar levels between themselves. Soil organic matter (OM) and soil pH had stronger effects on the N-cycling bacteria gene abundance. All bacterial gene concentrations and soil pH showed nonrandom distribution patterns with a 141‚Äď186 m range autocorrelation. These results indicate that biological N transformation processes are more important in natural agricultural systems and the abundance of N-cycling bacteria can be manipulated by field-scale management strategies

    Quantifying Aquatic Carbon and Nitrogen Dynamics and Greenhouse Gas Mitigation Potential in Riparian Agroforestry Zones

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    Agricultural intensification in Canada has led to a loss of riparian areas, which has resulted in the degradation of freshwater aquatic ecosystems due to an increasing amount of fertilizer and nutrients being introduced from the upland vegetation. Rehabilitation/restoration of the riparian areas has been shown to minimize these effects. The main objective of my research study is to quantify the carbon (C) and nitrogen (N) dynamics in the aquatic component of the Riparian Agroforestry Systems (RAFS) with varied vegetation located along Washington Creek, Ontario, Canada. The four different treatments studied had the following vegetation types: rehabilitated forest (RH), undisturbed natural forest dominated by deciduous vegetation (UNF-D), herbaceous vegetation (HB), or undisturbed natural forest dominated by coniferous vegetation (UNF-C). No significant spatial differences were found in the Carbon di-oxide concentrations of the RAFS. Among the four riparian treatments, UNF-C recorded significantly lower (p = 0.003) and HB recorded significantly higher (p = 0.002) Methane concentration. Stream DOC concentrations were different among the treatments, with UNF-C reporting significantly lower (p = 0.035) concentrations as compared to the other treatments. Sediment OC was the highest in the RH treatment, and lowest in the HB treatment. Among the four riparian treatments, HB recorded significantly lower (p = 0.024) and UNF-C recorded significantly higher (p = 0.000) Nitrous oxide concentration. Riparian zone averages for TN concentration show that on average UNF-C recorded significantly higher (p = 0.000) values compared to the other treatments, where other N species like ammonium and nitrate were not significantly different amongst treatments. Mean sediment ammonium concentrations were the highest in the RH treatment, along with stream TN. Stream nitrate concentrations were similar among the treatments. Even though the terrestrial morphology of the RH and UNF-D riparian zone were different, including vegetation type and buffer width, but the aquatic component morphology for parameters like discharge, pH, DO, water temperature were similar. Furthermore, the chemical composition of the water in these riparian streams, that is, the GHG concentrations and other C and N species, were insignificantly different. This finding is the highlight of this study. Despite the differences in the terrestrial component, RH, which is a shorter and younger rehabilitated buffer, is just as effective at improving the water quality as is a 100-year-old and much wider forested buffer UNF-D. Therefore, implementing RH buffers at a BMP could potentially lead to water quality improvement in an agricultural landscape

    Estabilización de lodos residuales en el camal Municipal de la Zona 1 provincia de Imbabura a través de un tratamiento biológico para su aprovechamiento como fertilizante orgánico

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    Estabilizar los lodos residuales del camal municipal de Ibarra a trav√©s de un proceso biol√≥gico para reducir la carga microbiol√≥gica y su posterior aprovechamiento como fertilizante org√°nico.Los lodos primarios procedentes del Camal Municipal de Ibarra son un subproducto del faenamiento animal. La falta de una legislaci√≥n adecuada en el Ecuador afecta la disposici√≥n final de estos residuos, mismos que sin un tratamiento previo pueden afectar paulatinamente el medio ambiente y la salud p√ļblica, debido a su elevado porcentaje de materia org√°nica putrescible, y microorganismos pat√≥genos. La aplicaci√≥n de tratamientos biol√≥gicos y qu√≠micos para la estabilizaci√≥n de lodos residuales constituyen una alternativa para su aprovechamiento como materia prima en la agricultura. En esta investigaci√≥n se obtuvo un fertilizante org√°nico a partir del lodo generado en la piscina de trampa de grasas de la empresa EPYPROCAI (Camal Municipal Ibarra) y se determin√≥ el efecto del fertilizante en el porcentaje de germinaci√≥n de semillas de Hordeum vulgare (cebada). Se trataron las muestras del lodo residual mediante digesti√≥n anaerobia a 30¬ļC y 50¬ļC variando las concentraciones del in√≥culo de los diferentes tratamientos. Para la cuantificaci√≥n de pat√≥genos se utiliz√≥ el m√©todo de recuento en placa con los medios selectivos para E. coli, Salmonella, Shigella y coliformes totales. Los par√°metros f√≠sicos, macronutrientes y micronutrientes se analizaron mediante ensayos fisicoqu√≠micos; el potencial de producci√≥n de metano se cuantific√≥ mediante el principio de desplazamiento volum√©trico utilizando una soluci√≥n alcalina. Se evalu√≥ la influencia del lodo estabilizado en cebada mediante un ensayo de fitotoxicidad en semillas e √≠ndice de germinaci√≥n en suelo. En los tratamientos MK1T1 (lodo + in√≥culo 100 cc), MK2T2 (lodo + in√≥culo 130 cc), y MK3T3 (lodo + in√≥culo 150 cc) a 50oC, se control√≥ de manera eficaz el crecimiento bacteriano de los pat√≥genos de inter√©s, sin embargo, en el control de los microorganismos pat√≥genos a 30oC se evidenci√≥ que hubo una reducci√≥n parcial de Salmonella y Shigella en los tratamientos MK1T1 y MK2T2, adem√°s, el tratamiento MK3T3 fue efectivo en la reducci√≥n de E.coli, cabe destacar que ninguno de los tratamientos fue eficiente en la eliminaci√≥n de coliformes fecales. La mayor cantidad de metano producida durante la digesti√≥n anaerobia pertenece al tratamiento MK3T3 a 50oC, los valores del contenido de materia org√°nica y la relaci√≥n C/N permanecieron altos al finalizar el proceso de degradaci√≥n de la materia org√°nica por lo que cumple con los niveles adecuados para un fertilizante de buena calidad, en la evaluaci√≥n del fertilizante org√°nico el ensayo de fitotoxicidad MK2N1 obtuvo el mayor porcentaje de germinaci√≥n (96,67%) e √≠ndice de la tasa de germinaci√≥n, mientras que el ensayo MK2N3 tuvo el menor √≠ndice de germinaci√≥n (50%), y no se observ√≥ diferencias estad√≠sticamente significativas del √≠ndice de vigorosidad de las pl√°ntulas evaluadas. Se estudiaron caracter√≠sticas morfol√≥gicas cuantitativas de las pl√°ntulas de cebada, las variables longitud de la ra√≠z y altura de la planta presentaron diferencias significativas siendo el tratamiento MK2T2L2 superior en las variables mencionadas al resto de tratamientos.Ingenier√≠

    Nanobubble aeration enhanced wastewater treatment and bioenergy generation in constructed wetlands coupled with microbial fuel cells

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    Artificial aeration is a widely used approach in wastewater treatment to enhance the removal of pollutants, however, traditional aeration techniques have been challenging due to the low oxygen transfer rate (OTR). Nanobubble aeration has emerged as a promising technology that utilise nano-scale bubbles to achieve higher OTRs owing to their large surface area and unique properties such as longevity and reactive oxygen species generation. This study, for the first time, investigated the feasibility of coupling nanobubble technology with constructed wetlands (CWs) for treating livestock wastewater. The results demonstrated that nanobubble-aerated CWs achieved significantly higher removal efficiencies of total organic carbon (TOC) and ammonia (NH4+-N), at 49 % and 65 %, respectively, compared to traditional aeration treatment (36 % and 48 %) and the control group (27 % and 22 %). The enhanced performance of the nanobubble-aerated CWs can be attributed to the nearly three times higher amount of nanobubbles (√ė < 1 őľm) generated from the nanobubble pump (3.68 √ó 108 particles/mL) compared to the normal aeration pump. Moreover, the microbial fuel cells (MFCs) embedded in the nanobubble-aerated CWs harvested 5.5 times higher electricity energy (29 mW/m2) compared to the other groups. The results suggested that nanobubble technology has the potential to trigger the innovation of CWs by enhancing their capacity for water treatment and energy recovery. Further research needs are proposed to optimise the generation of nanobubbles, allowing them to be effectively coupled with different technologies for engineering implementation

    Optimierung von D√ľngungs- und Bewirtschaftungsstrategien im Gem√ľsebau zur Minderung von Stickstoffemissionen

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    To ensure a high yield and quality of the produce, a high fertilizer nitrogen (N) supply is often required in vegetable crop rotations. However, the fertilizer N requirement is difficult to calculate since the N supply via mineralization and actual N uptake of the crop cannot accurately be predicted in advance. Therefore, base fertilization and top dressing are usually applied before intensive N uptake starts. However, if a crop is harvested before yield expectations are reached, this strategy can result in high soil mineral N residues. In addition, high quantities of N-rich and readily mineralizable crop residues often remain in the field at harvest. In sandy soils, however, nitrate can be easily leached. Other significant N losses are caused by gaseous ammonia volatilization and nitrous oxide emission. However, the emission of these N species can directly and indirectly damage ecosystems, contribute to global warming, and contaminate sources of drinking water. The first part of this study aimed at the risk of nitrate leaching losses during the cultivation of field-grown spinach. Therefore, the effect of a reduced N base fertilization as well as a split N top dressing was examined in a series of fertilization trials. The reduced base fertilization was compensated by an increased top dressing based on the soil mineral N concentration. In a further treatment the second top dressing of 50‚Äď70 kg N/ha was applied by a frequent urea foliar spraying instead of the single application of a granulated nitrate fertilizer. A further part of this thesis focused on reducing post-harvest N losses following autumn-grown spinach during the winter leaching period. For this purpose, the depth, frequency, and timing of the incorporation of the spinach crop residues were varied. Furthermore, the effectiveness of spraying the crop residues with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) was examined. The results showed that both reducing the base fertilization and splitting the top dressing significantly decreased the nitrate concentration exposed to leaching. In addition, the splitting approach made it possible to dispense with the second top dressing in the case of harvesting at an early harvest stage. Thus, the soil mineral N residues were reduced. On the other hand, these measures diminished the crop yield at an early harvest stage by 6% on average. At a late harvest stage, spinach was less affected by the schedule of the fertilizer N supply. Due to diminished plant growth and necrosis at the leaf margin, a frequent urea foliar spray proved to be an inappropriate fertilization strategy in contrast to the application of a granulated fertilizer in combination with a subsequent irrigation. In spring-grown and winter-grown spinach, nitrogen was one of the most limiting growth factors. In contrast, in the summer and autumn seasons marketable yield appeared to be limited by bolting and decreasing irradiation, respectively. Thus, in these seasons it was possible to dispense with the second top dressing without affecting the marketable yield. Within a few weeks after the incorporation of the spinach crop residues an intensive mineralization increased the soil nitrate concentration up to 100 kg N/ha (0‚Äď90 cm). Even the treatment of the crop residues with DMPP was hardly able to delay nitrate formation. In addition, the winter cover crops only partially absorbed the soil mineral N. As a result, high quantities of nitrate shifted down the soil profile during the winter leaching period. Based on an N balance sheet, potential N losses were mostly independent of the tillage intensity. In contrast, by postponing the incorporation of the crop residues from early autumn to spring the potential N losses were reduced to ‚ȧ 20 kg/ha. This effect was due to the N uptake and N conservation of the resprouting spinach crop residues as well as the lower net N mineralization in the soil. However, when the spinach plants partially or completely decomposed in autumn and winter, the potential N losses were considerable even without tillage. To ensure N uptake and a low N mineralization a superficial sowing of a winter hard catch crop into the resprouting spinach crop residues without soil disturbances seems to be a promising approach. Unlike open-field cultivation, nitrate leaching losses can be effectively reduced by cultivation in soilless closed-loop irrigation systems. However, organic cultivation of fast-grown crops like basil is challenging in such systems since N supply is dependent on the mineralization of organic fertilizers in a small substrate volume. To ensure a sufficient N availability, high quantities of organic N are applied to the growing media. However, depending on the mineralization rate, this can lead to plant damage and yield depressions. Based on this background, in the third part of this thesis it was examined whether pot-grown basil is affected by ammonia and ammonium exposures resulting from an organic fertilization. Therefore, basil was cultivated at different base N fertilization and substrate pH levels. The growing media consisted of pure peat or a mixture of peat and 5% (v/v) mature green waste compost. A high base fertilization as well as high substrate pH caused considerable damage to basil seedlings and diminished crop growth. These observations were mainly explained by the ammonical exposure. Thus, both a reduced base fertilization and lower initial substrate pH mitigated these effects. However, optimum plant growth was only achieved by the amendment of compost. In addition, the peat-compost mixture had to be stored for about two weeks before sowing. In this approach an early initiation of the nitrification led to a fast and effective reduction of the ammonia and ammonium exposures right from the seedling stage. Furthermore, the resulting increased nitrate supply promoted basil growth. Due to the variety of organic fertilizers and substrate components used in organically grown crops, further trials are required to make general recommendations. The optimized synchronization of N demand and N supply proved to be effective in reducing potential nitrate leaching losses in open fields as well as prevent harmful exposures to ammonia and ammonium in organically pot-grown basil. However, the development of specific plant and soil monitoring technologies seems to be necessary to better estimate whether the N fertilization can be delayed or even the total N supply can be reduced without affecting marketable yield in individual cases. Quantitatively, most N losses were observed in the off-season during the winter leaching period. A holistic approach to reducing N losses and emissions into the environment must therefore also include the post-harvest strategy

    Comparison between biofloc technology system and aquamimicry in the cultivation of Litopenaeus vannamei in lined ponds in Southern Brazil

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    This work compared biofloc technology and aquamimicry technologies in Litopenaeus vannamei lined ponds, using a density of 60 shrimp¬∑m-2. The experiment lasted 120 days, with two treatments, bioflocs (TBio) and aquamimicry (TMi), and three replications for each. In both treatments, the average values of the water quality parameters were as follows: temperature was 24.0 ¬Ī 0.32 ¬įC, dissolved oxygen was 8.00 ¬Ī 0.45 mg¬∑L-1, pH was 8.40 ¬Ī 0.20, and alkalinity was 240.01 ¬Ī 37.15 mg¬∑L-1. The control of water quality was effectively maintained in both treatments, indicating the aquamimicry system‚Äôs capability to efficiently recycle the nutrients found in the lined ponds‚Äô water. Furthermore, both treatments demonstrated efficiency in shrimp production, and the shrimp from the TMi treatment reached an average final weight of 11.73 ¬Ī 2.21 g, average survival of 53.3 ¬Ī 15.2%, and productivity of 3.56 ¬Ī 0.15-ton¬∑ha-1. The TBio shrimp reached a final weight of 11.48 ¬Ī 1.25 g, survival of 63.3 ¬Ī 8.16%, and productivity of 4.08 ¬Ī 1.10-ton¬∑ha-1. The present study demonstrated that TMi treatment pondspresented zootechnical performances close to those of TBio treatment ponds. The results achieved can contribute to the improvement of this cultivation system to use it in higher stocking densities

    EVALUATION OF CHEMICAL CONTROL OPTIONS, ENVIRONMENTAL FACTORS, AND MANAGEMENT PRACTICES ASSOCIATED WITH ANGULAR LEAF SPOT (\u3ci\u3ePSEUDOMONAS SYRINGAE\u3c/i\u3e PV. \u3ci\u3eTABACI\u3c/i\u3e)

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    Pseudomonas syringae pv. tabaci tox- is the causal agent of angular leaf spot in dark tobacco. Since 2015, angular leaf spot has become the most significant foliar disease in dark tobacco production in Kentucky and Tennessee. Dark tobacco producers utilize one main tool, streptomycin sulfate, for the management of this bacterial disease. Resistance to streptomycin sulfate in P. syringae pv. tabaci isolates from dark tobacco fields in western Kentucky was first observed in 2015. Field spray trials were developed to evaluate the efficacy of alternative active ingredients compared to the grower‚Äôs standard, streptomycin sulfate. Two separate field trials were conducted in 2020, 2021, and 2022 to evaluate the efficacy of 10 different chemical control options for the management of angular leaf spot. The first field trial investigated streptomycin sulfate, laminarin, cuprous oxide, Reynoutria sachalinensis, peroxyacetic acid, polyoxin D zinc salt, Ulocladium oudemansii strain U3, and acibenzolar-S-methyl for the management of angular leaf spot. The second field trial was established to evaluate the efficacy of streptomycin sulfate, cuprous oxide, copper sulfate pentahydrate, and copper octanoate for management of angular leaf spot. In all trials and years, dark tobacco variety KT D8LC was utilized, as this tobacco variety had previously shown susceptibility to angular leaf spot. There are no dark tobacco varieties resistant to angular leaf spot. Plots in all years were inoculated with a streptomycin sulfate sensitive isolate of P. syringae pv. tabaci to ensure disease pressure. Field trials that evaluated streptomycin sulfate, laminarin, cuprous oxide, Reynoutria sachalinensis, peroxyacetic acid, polyoxin D zinc salt, Ulocladium oudemansii strain U3, and acibenzolar-S-methyl, data analysis showed that the streptomycin sulfate performed similarly to the untreated control in most trials. No treatment eliminated this bacterial disease. Untreated tobacco, tobacco treated with polyoxin D zinc salt or peroxyacetic acid had significantly higher area under the disease progress curve than other treatments during the three-year study. No significant yield differences were observed in 2020 for area under the disease progress curve. In 2022, there were significant differences in yield. Tobacco treated with cuprous oxide followed by Reynoutria sachalinensis and the recommended spray regimen had significantly higher yields compared to 10 of the remaining 12 treatments. Implementing a spray regimen with varying active ingredients and modes of action is key in preventing pathogen resistance and decreasing the intensity of angular leaf spot. Field trials that evaluated the efficacy of streptomycin sulfate, cuprous oxide, copper sulfate pentahydrate, and copper octanoate data analysis showed that in two of the three years, tobacco treated with cuprous oxide had numerically higher yields compared to tobacco treated with streptomycin sulfate. In 2021 and 2022, tobacco treated with cuprous oxide also had numerically higher quality grade index compared to streptomycin sulfate, and in 2020, these differences were significant. An observational study was conducted in 2020, 2021, and 2022 to evaluate possible correlations between grower management practices, environmental factors, and angular leaf spot. Ninety fields were monitored in this three-year study. Fields were located in seven counties in Western Kentucky and northwestern Tennessee. Growers were not asked to implement new practices or change any current practices in their management program. Four fields were confirmed to have ALS in 2020, eight fields were confirmed in 2021, and four fields were confirmed in 2022. Correlations occurred between angular leaf spot presence and three nutrients found in plant tissue: phosphorus, boron, and copper; and three nutrients found in soil: sulfur, manganese, and copper. An increased probability of angular leaf spot was also found to occur if the average temperature increases by 1¬įC . With one degree C increase in average air temperature, the chance of angular leaf spot being detected increases by approximately 47%. Further research needs to be conducted in years with higher frequencies of angular leaf spot to make grower recommendations regarding nutrient recommendations. Increasing frequency of fields containing angular leaf spot are needed to make further correlations between environmental and management factors
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