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Charakterisierung mikrobieller Gemeinschaften in ehemaligen, neutralen Uranerzbergwerken in Sachsen und Untersuchungen zur mikrobiellen Immobilisierung von Uran und ArsenGagell, Corinna 12 January 2016 (has links) (PDF)
Ehemalige Urangruben tragen durch das anfallende Flutungswasser maßgeblich zur Ausbreitung von Schadstoffen wie Uran und Arsen in teils dicht besiedelte Gebiete bei. Um die Prozesse in den unterirdischen Gruben besser zu verstehen und alternative Strategien zur konventionellen, kostenintensiven Wasserbehandlung entwickeln zu können, war das Ziel der Arbeit, mikrobielle Gemeinschaften aus drei gefluteten Uranerzbergwerken in Sachsen, namens Pöhla, Schlema und Zobes, die unterschiedliche Flutungsstadien repräsentierten, zu charakterisieren und den mikrobiellen Einfluss auf die Mobilität von Uran und Arsen zu untersuchen.
Um herauszufinden, welche Mikroorganismen die hydrochemischen Vorgänge im Untergrund der Uranerzbergwerke beeinflussen könnten, wurde die Diversität und Zusammensetzung mikrobieller Gemeinschaften mittels Pyrosequenzierung eines Fragments des 16S rRNA Gens (16S rDNA) und CARD-FISH ermittelt. Wenngleich Clusteranalysen zeigten, dass sich die planktonischen Gemeinschaften hinsichtlich ihrer bakteriellen Zusammensetzung zwischen den drei Uranerzbergwerken unterschieden, wurden alle von chemolithotrophen Schwefeloxidierern der Beta- und Epsilonproteobacteria dominiert, die mit den Gattungen Thiobacillus und Sulfuritalea bzw. Sulfuricurvum und Sulfurimonas vertreten waren. Im Unterschied zu den planktonischen Gemeinschaften bestanden in situ Biofilme, die auf BACTRAPs während einer 3-monatigen Exposition im Flutungswasser anwuchsen, laut Pyrosequenzierung zu einem wesentlichen, mitunter dominanten Anteil aus metall- bzw. sulfatreduzierenden Deltaproteobacteria. In Biofilmgemeinschaften aus Zobes wurden hauptsächlich Geobacter sp. detektiert, die als Fe(III)- und U(VI)-Reduzierer bekannt sind. Obwohl Archaea basierend auf den Ergebnissen der CARD-FISH-Analyse nur einen sehr geringen Anteil der planktonischen Gemeinschaften ausmachten, wurden mittels Pyrosequenzierung planktonische Euryarchaeota der Thermoprotei in allen Gruben detektiert. In planktonischen Gemeinschaften und 3-monatigen Biofilmen aus Pöhla und Zobes wurden zudem methanogene Crenarchaeota, vor allem Methanobacteria und teilweise Methanomicrobia, ermittelt. Die 16S rRNA-Analyse, die ergänzend zum DNA-basierten Ansatz durchgeführt wurde, lieferte Hinweise darauf, dass die detektierten, dominanten Mikroorganismen, Bacteria sowie Archaea, in der planktonischen Gemeinschaft aus Schlema und den Biofilmgemeinschaften stoffwechselaktiv waren. In der planktonischen Gemeinschaft aus Zobes wurden im Vergleich zur DNA-basierten Analyse höhere Abundanzen für Verrucomicrobia, Acidobacteria und Alphaproteobacteria ermittelt, deren Bedeutung offen bleibt.
Untersuchungen zum mikrobiellen Stoffwechselpotential planktonischer Gemeinschaften mittels CFU- und MPN-Analysen ergaben, dass Mikroorganismen aus allen Urangruben ein breites Spektrum anaerober Reaktionen (Nitrat-, Eisen-, Mangan-, Arsenat- und Sulfatreduktion und Acetogenese) unter Laborbedingungen abdeckten. In guter Übereinstimmung mit den Sequenzierungsergebnissen konnten methanogene Mikroorganismen nur im Flutungswasser aus Pöhla und Zobes detektiert werden.
Die Metaproteomanalyse ergab, dass 61,6% der Peptide in der planktonischen Gemeinschaft aus Schlema von den dominanten Epsilonproteobacteria stammten. Dagegen wurden für Zobes detektierte Peptide mehrheitlich methylotrophen und eisenoxidierenden Betaproteobacteria der Familien Methylophilaceae bzw. Gallionellaceae sowie methylotrophen Gammaproteobacteria der Methylococcaceae zugewiesen. Obwohl die Mehrheit der Proteine an der Translation beteiligt war, konnten insgesamt 49 Proteingruppen ermittelt werden, deren Vertreter für den mikrobiellen Energiestoffwechsel relevant waren. Insbesondere planktonische Gammaproteobacteria aus Zobes konnten so mit dem Kohlenstoff- und Schwefelkreislauf in Zusammenhang gebracht werden.
Mithilfe von Labormikrokosmen wurde der potentielle Einfluss mikrobieller Gemeinschaften aus Schlema auf die Mobilität von Arsen und Uran im Flutungswasser mit Acetat als Elektronendonor unter anaeroben Bedingungen über einen Zeitraum von 98 Tagen untersucht. Im Vergleich zu den Kontrollen konnten sowohl die stimulierte, planktonische Gemeinschaft als auch Biofilme natürliches Arsen aus der wässrigen Phase fast vollständig entfernen. Allerdings wies der spätere Anstieg des gelösten Arsens daraufhin, dass der immobilisierte Zustand langfristig nicht stabil blieb. In stimulierten Biofilm-Ansätzen wurde Uran mit bis zu 39 ± 9% (in Anwesenheit von 7 µM natürlichem Uran) bzw. 34 ± 8% (bei Zugabe von 50 µM U(VI)) aus der wässrigen Phase langfristig (98 Tage) immobilisiert. Laserfluoreszenzspektroskopische Untersuchungen zeigten, dass Uran im Biofilm reduziert wurde.
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Soil nitrogen and phosphorus depletion as a means of restoring degraded lowland fynbos ecosystems invaded by alien grassesRuwanza, Sheunesu 03 1900 (has links)
Thesis (MSc (Conservation Ecology and Entomology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Much of South African lowland fynbos vegetation has been transformed by agriculture and invasive alien grass species. The artificial reduction of plant available N and P levels in soils, through the addition of carbon and calcium respectively, may provide a means of retarding the growth of alien grasses stimulated by soil nutrient enrichment. Furthermore, the competitive advantage of native lowland fynbos species adapted to nutrient impoverished soils may be increased by these additions.
The above premise was tested in both field- and greenhouse-based trials by applying systemic and contact herbicides to reduce the large alien invasive grass biomass. This was followed by the addition of C as sucrose and Ca as gypsum to reduce plant available N and P respectively in the soils. The effects of these combined herbicide and soil nutrient amendment treatments on plant physiology and growth were examined in both resident alien and indigenous species and in several herbaceous and woody native species introduced as seeds and seedlings. Also, soils sampled from the different treatments in both trials were chemically analyzed. There was a total absence of seedling recruitment from seeds of all 9 indigenous species sown into soils in the field-based trial while introduced juveniles of another 9 indigenous species displayed a high mortality during the dry summer season. These detrimental effects were less severe in the greenhouse-based trial which received more regular watering and where successful seedling recruitment from seeds sown occurred in four indigenous species. Sucrose additions, both exclusively and in combination with gypsum, caused significant reductions in foliar chlorophyll, photosystem II (PSII) function and above-ground biomass of most resident and introduced alien and indigenous species. These reductions were less prominent where herbicides were applied, a possible consequence of N and P supplementation of soils by the decomposing plant biomass. This was supported by the elevated soil K, Na and N concentrations measured in soils where contact and systemic herbicides were applied. However, no significant changes in soil N or P were apparent following sucrose and gypsum additions respectively, the latter attributed to the acidic soils which precluded the formation of insoluble P complexes.
A second study tested the hypothesis that exogenous sucrose addition to soils inhibits plant growth by stimulating soil microbial biomass which accumulates soil nitrogen rendering it unavailable to plants. Two native, early seral species (Dimorphotheca pluvialus (L.) Moench and Ursinia anthemoides (L) Poir. subsp anthemoides) were cultured in heat sterilized (2200C for 72 hours) and non-sterilized soils in a greenhouse under four different levels of sucrose (0, 100, 200 and 300 g m-2) supplied monthly over a four-month active growing period. Foliar chlorophyll
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contents, photosystem II (PSII) efficiencies, shoot and root lengths and dry mass, inflorescence numbers and N and P contents were measured in the plants, and N and P contents and bacterial cell and coliform numbers analyzed in the soils. Both D. pluvialis and U. anthemoides displayed significant reductions in PSII efficiency, chlorophyll content, accumulation of biomass and N and P in response increased levels of sucrose, which initially seemingly supported the hypothesis as these reductions were of substantially greater magnitude in plants cultivated in non-sterilized than sterilized soils. Despite this, there was no evidence of any significant increases in bacterial and coliform cell numbers in response to increased levels of sucrose supplied or any significant reductions in soil N and P contents following sucrose additions in both sterile and non-sterilized soils. Greater numbers of bacteria and coliforms were measured in sterilized than non-sterilized soils which corresponded with reduced soil N contents but these were not reflected in like changes in plant PSII efficiency and growth and total amounts of N taken up by plants which displayed massive increases in sterilized soils. The findings did not support the hypothesis and pointed to an abiotic mechanism of sucrose inhibition of plant photosynthesis and growth.
The study concludes that the suitability of adding sucrose and gypsum to degraded renosterveld ecosystem soils to promote the competitiveness of native taxa against alien grasses is dubious. Other restoration alternatives such as natural re-colonization, transfer of soils containing viable seeds from pristine communities and top soil removal should be considered. / AFRIKAANSE OPSOMMING: Baie van Suid Afrika se laagland fynbos plantegroei is verander deur landbou en uitheemse indringer grasspesies. Die kunsmatige reduksie van plantbeskikbare N en P vlakke in die grond deur die toevoeging van koolstof en kalsium onderskeidelik, kan ’n metode wees om die groei van indringer grasse te vertraag, wat gestimuleer word deur grondvoedingstofverryking. Die kompeterende voordeel van die inheemse laagland fynbosspesies wat aangepas is tot voedingstofarme grond kan verhoog word deur die toevoegings.
Bogenoemde postulaat is in beide die veld- en die glashuis-gebaseerde eksperimente getoets deur die aanwending van sistemiese en kontak onkruiddoder om die groot indringer grasbiomassa te verminder gevolg deur die byvoeging van C as sukrose en Ca as gips om die plantbeskibare N en P onderskeidelik te verminder in die grond. Die effekte van die gekombineerde onkruiddoder en grondvoedingstof verbeteringsbehandelings op die fisiologie en groei van die plante is ondersoek in beide inheemse- en residente indringerspesies asook in verskeie kruidagtige- en houtagtige inheemse spesies wat aangeplant was as sade en saailinge. Grondmonsters van die verskillende behandelings in beide studies was versamel en was chemies geanaliseer. Daar was ’n definitiewe afwesigheid van nuwe saailinge van sade van al nege indringerspesies wat gesaai was in grond in die veldgebaseerde studie, en saailinge van nog nege inheemse spesies het ’n hoë mortaliteit getoon gedurende die droë somerseisoen. Hierdie skadelike effekte was minder ernstig in die glashuisgebaseerde studie wat meer benat was, en waar nuwe saailinge suksesvol geproduseer was deur sade in vier inheemse spesies. Sukrose byvoegings, beide uitgesluit en in kombinasie met gips, het ’n afname in blaarchlorofil, fotosisteem II en bogrondse biomassa van die meeste van die residente en aangeplante indringer- en inheemse spesies getoon. Hierdie afnames was minder prominent waar onkruiddoder aangewend was, ’n moontlke oorsaak van N en P aanvulling van grond deur die verrottende plantbiomassa. Dit word ondersteun deur verghoogde grond K, Na en N konsentrasies, gemeet in grond waar kontak en sistemiese onkruiddoder toegevoeg was. Geen noemenswaardige veranderinge in grond N of P was sigbaar na byvoeging van sukrose en gips onderskeidelik nie. Laasgenoemde het bygedra tot suuragtige grond wat die formasie van onoplosbare P komplekse verkom het.
‘n Tweede studie het die hipotese getoets waar eksogene sukrose byvoeging tot grond plantegroei inhibeer deur die grond mikrobe biomassa te stimuleer wat akkumuleer wat in grond stikstof en dit nie beskikbaar maak vir plante nie.Twee inheemse vroeë intermediêre stadium spesies (Dimorphotheca pluvialus (L.) Moench en Ursinia anthemoides (L) Poir. subsp v
anthemoides) was gekweek in hitte gesteriliseerde grond (2200 C vir 72 uur) en in nie-gesteriliseerde grond in ’n glashuis onder vier verskillende vlakke van van sukrose (0, 100, 200 en 300 g m-2) bygevoeg maandeliks oor ‘n 4 maande aktiewe groei periode. Blaarchlorofilinhoud, fotosisteem II (FS II) doeltreffendheid, groeipunt en wortel lengte en droë massa, blomgetalle en N en P inhoud was gemeet in die plante sowel as N en P inhoud en bakteriële sel en kolivorm getalle was geanaliseer in die grond. Beide D. pluvialis en U . anthemoides het ’n afname getoon in FS II doeltreffendheid, chlorofilinhoud, biomassa akkumulasie, N en P response op verhoogde vlakke van sukrose, wat aanvanklik aangetoon het dat dit die hipotese ondersteun want hierdie afnames wat heelwat groter in plante wat gekweek was in ongesteriliseerde grond as in gesteriliseerde grond. Daar was geen toename in baketriële en kolivorm sel getalle in rssponse tot verhoogde vlakke van sukrose byvoegings of enige noemenswaardige in grond N en P inhoud na byvoeging van sukrose in beide steriele en nie-steriele grond nie. Groot getalle bakterieë en kolivorme was gemeet in gesteriliseerde grond as in ongesteriliseerde grond. Dit korrespondeer met verminderde grond N inhoud maar dit was nie gereflekteer in veranderinge in plant FS II doeltreffendheid, groei en die totale hoeveelhede N wat opgeneem was deur plante wat ’n massiewe toename getoon het ongesteriliseerde grond nie. Hierdie bevindings het nie die hipotese ondersteun nie en het gewys na ’n abiotiese meganisme van sukrose inhibisie van plant fotosintese en groei.
Die studie lei dus af dat die geskiktheid om sukrose en gips by te voeg tot gedegradeerde renosterveld ekosisteemgrond om kompetisie tussen inheemse plante en indringer grasse te promoveer, twyfelagtig is. Ander restorasie alternatiewe soos natuurlike herkolonisasie, oordrag van grond wat lewensvatbare sade bevat van onbeskadigde gemeenskappe en bogrond verwydering word oorweeg.
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Charakterisierung mikrobieller Gemeinschaften in ehemaligen, neutralen Uranerzbergwerken in Sachsen und Untersuchungen zur mikrobiellen Immobilisierung von Uran und ArsenGagell, Corinna 03 November 2015 (has links)
Ehemalige Urangruben tragen durch das anfallende Flutungswasser maßgeblich zur Ausbreitung von Schadstoffen wie Uran und Arsen in teils dicht besiedelte Gebiete bei. Um die Prozesse in den unterirdischen Gruben besser zu verstehen und alternative Strategien zur konventionellen, kostenintensiven Wasserbehandlung entwickeln zu können, war das Ziel der Arbeit, mikrobielle Gemeinschaften aus drei gefluteten Uranerzbergwerken in Sachsen, namens Pöhla, Schlema und Zobes, die unterschiedliche Flutungsstadien repräsentierten, zu charakterisieren und den mikrobiellen Einfluss auf die Mobilität von Uran und Arsen zu untersuchen.
Um herauszufinden, welche Mikroorganismen die hydrochemischen Vorgänge im Untergrund der Uranerzbergwerke beeinflussen könnten, wurde die Diversität und Zusammensetzung mikrobieller Gemeinschaften mittels Pyrosequenzierung eines Fragments des 16S rRNA Gens (16S rDNA) und CARD-FISH ermittelt. Wenngleich Clusteranalysen zeigten, dass sich die planktonischen Gemeinschaften hinsichtlich ihrer bakteriellen Zusammensetzung zwischen den drei Uranerzbergwerken unterschieden, wurden alle von chemolithotrophen Schwefeloxidierern der Beta- und Epsilonproteobacteria dominiert, die mit den Gattungen Thiobacillus und Sulfuritalea bzw. Sulfuricurvum und Sulfurimonas vertreten waren. Im Unterschied zu den planktonischen Gemeinschaften bestanden in situ Biofilme, die auf BACTRAPs während einer 3-monatigen Exposition im Flutungswasser anwuchsen, laut Pyrosequenzierung zu einem wesentlichen, mitunter dominanten Anteil aus metall- bzw. sulfatreduzierenden Deltaproteobacteria. In Biofilmgemeinschaften aus Zobes wurden hauptsächlich Geobacter sp. detektiert, die als Fe(III)- und U(VI)-Reduzierer bekannt sind. Obwohl Archaea basierend auf den Ergebnissen der CARD-FISH-Analyse nur einen sehr geringen Anteil der planktonischen Gemeinschaften ausmachten, wurden mittels Pyrosequenzierung planktonische Euryarchaeota der Thermoprotei in allen Gruben detektiert. In planktonischen Gemeinschaften und 3-monatigen Biofilmen aus Pöhla und Zobes wurden zudem methanogene Crenarchaeota, vor allem Methanobacteria und teilweise Methanomicrobia, ermittelt. Die 16S rRNA-Analyse, die ergänzend zum DNA-basierten Ansatz durchgeführt wurde, lieferte Hinweise darauf, dass die detektierten, dominanten Mikroorganismen, Bacteria sowie Archaea, in der planktonischen Gemeinschaft aus Schlema und den Biofilmgemeinschaften stoffwechselaktiv waren. In der planktonischen Gemeinschaft aus Zobes wurden im Vergleich zur DNA-basierten Analyse höhere Abundanzen für Verrucomicrobia, Acidobacteria und Alphaproteobacteria ermittelt, deren Bedeutung offen bleibt.
Untersuchungen zum mikrobiellen Stoffwechselpotential planktonischer Gemeinschaften mittels CFU- und MPN-Analysen ergaben, dass Mikroorganismen aus allen Urangruben ein breites Spektrum anaerober Reaktionen (Nitrat-, Eisen-, Mangan-, Arsenat- und Sulfatreduktion und Acetogenese) unter Laborbedingungen abdeckten. In guter Übereinstimmung mit den Sequenzierungsergebnissen konnten methanogene Mikroorganismen nur im Flutungswasser aus Pöhla und Zobes detektiert werden.
Die Metaproteomanalyse ergab, dass 61,6% der Peptide in der planktonischen Gemeinschaft aus Schlema von den dominanten Epsilonproteobacteria stammten. Dagegen wurden für Zobes detektierte Peptide mehrheitlich methylotrophen und eisenoxidierenden Betaproteobacteria der Familien Methylophilaceae bzw. Gallionellaceae sowie methylotrophen Gammaproteobacteria der Methylococcaceae zugewiesen. Obwohl die Mehrheit der Proteine an der Translation beteiligt war, konnten insgesamt 49 Proteingruppen ermittelt werden, deren Vertreter für den mikrobiellen Energiestoffwechsel relevant waren. Insbesondere planktonische Gammaproteobacteria aus Zobes konnten so mit dem Kohlenstoff- und Schwefelkreislauf in Zusammenhang gebracht werden.
Mithilfe von Labormikrokosmen wurde der potentielle Einfluss mikrobieller Gemeinschaften aus Schlema auf die Mobilität von Arsen und Uran im Flutungswasser mit Acetat als Elektronendonor unter anaeroben Bedingungen über einen Zeitraum von 98 Tagen untersucht. Im Vergleich zu den Kontrollen konnten sowohl die stimulierte, planktonische Gemeinschaft als auch Biofilme natürliches Arsen aus der wässrigen Phase fast vollständig entfernen. Allerdings wies der spätere Anstieg des gelösten Arsens daraufhin, dass der immobilisierte Zustand langfristig nicht stabil blieb. In stimulierten Biofilm-Ansätzen wurde Uran mit bis zu 39 ± 9% (in Anwesenheit von 7 µM natürlichem Uran) bzw. 34 ± 8% (bei Zugabe von 50 µM U(VI)) aus der wässrigen Phase langfristig (98 Tage) immobilisiert. Laserfluoreszenzspektroskopische Untersuchungen zeigten, dass Uran im Biofilm reduziert wurde.
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Predição da necessidade de fertilizante nitrogenado pela cana-de-açúcar e reações do nitrogênio orgânico e mineral dissolvidos em palha e solo de canaviais / Predicting nitrogen fertilizer needs for sugarcane and reactions of dissolved organic and mineral nitrogen in straw and soil from sugarcane fieldsMariano, Eduardo 09 February 2015 (has links)
A recomendação de doses de nitrogênio (N) para a cana-de-açúcar (Saccharum spp.) com base em testes de solo é essencial para o aumento da sustentabilidade desse agroecossistema. Além disso, pouco se conhece sobre as reações do N orgânico dissolvido (NOD) na zona de transição palha-solo nos canaviais. A influência das formas minerais de N (N-NH4+ e N-NO3-) na mineralização de carbono (C) nessa região transitória também é desconhecida. Desse modo, os objetivos do estudo foram: i) correlacionar diversos métodos para a predição do N mineralizável do solo com parâmetros de resposta da cana-de-açúcar ao N; ii) quantificar os processos de mineralização de C e sorção de compostos do NOD aplicados em palha e solo (ambos amostrados na zona de transição); e iii) determinar a mineralização C e o conteúdo de N mineral em palha e solo de cana-de-açúcar (provenientes da zona de transição) pela adição de 14C-glicose associada ou não à fontes minerais de N. Entre 2006 e 2013 foram instalados 21 experimentos de curva de resposta da cana-de-açúcar ao N no Estado de São Paulo, Brasil, para correlacionar métodos de natureza biológica, química, microbiológica e isotópica (15N), com a produtividade de colmos (PCC) e extração de N (ENC) no tratamento controle, produção relativa da cultura (PRC) e com a dose de N necessária para obtenção de 90% da PRC (DN 90% PRC). As amostragens de solo foram realizadas nas camadas de 0-20 e 20-40 cm. Foram detectadas fracas correlações entre a incubação anaeróbia e a PCC, e o N extraível por KCl a quente por 4 h e o N extraível por tampão fosfato-borato a pH 11,2 com a ENC. Os métodos não se correlacionaram com a PRC e a DN 90% PRC. Nenhum método é recomendado no ajuste de doses de N para aplicação em soqueiras de cana-de-açúcar no Estado de São Paulo. Para o estudo das reações do NOD e do N mineral, amostras de palha e solo foram coletadas na região de transição entre os dois materiais, em dois sítios experimentais localizados no Estado de São Paulo. A mineralização de C e sorção de mistura de aminoácidos, peptídeos, ureia e proteína (todos marcados em 14C) foi determinada pela aplicação dos compostos em palha e solo. A mineralização de C e conteúdo de N mineral pela adição de 14C-glicose com ou sem as formas de N mineral (N-NH4+ e N-NO3-) também foi avaliada. Existem diferenças acentuadas entre a palha e solo relacionadas à dinâmica do NOD, perfil da comunidade microbiana e imobilização de N. Em geral, o conteúdo de 14C restante dos compostos do NOD foi maior no solo em relação à palha. Os peptídeos e a ureia apresentaram rápida mineralização de C, enquanto que a sorção da proteína foi maior no solo em comparação com a palha. A associação da 14C-glicose com N-NO3- resultou em maior mineralização de 14C na palha de ambos os sítios. Ocorreu intensa imobilização de N-NH4+, sobretudo no resíduo de cana-de-açúcar. / Recommendation of nitrogen (N) rates for sugarcane (Saccharum spp.) based upon soil testing is essential for increasing the sustainability of this agroecosystem. In addition, little is known about the dynamics of dissolved organic nitrogen (DON) in the straw-soil transition zone in sugarcane fields. The influence of mineral N forms in the carbon (C) mineralization in this transitional region is also unknown. Thus, the objectives of this study were: i) correlate several methods to predict the soil mineralizable N with sugarcane N response parameters; ii) quantifying the C mineralization and sorption processes of DON compounds applied to straw and soil (both sampled in the transition zone); and iii) determine the C mineralization and mineral N content in straw and soil (from the transition zone) by addition of 14C-glucose with or without mineral sources of N. Between 2006 and 2013, 21 sugarcane N response trials were performed in the State of São Paulo, Brazil, to correlate biological, chemical, microbiological and isotopic (15N) methods with stalks yield (SYC) and total N uptake (NUC) in the control treatment, relative stalks yield (RSY) and the N rate required to achieve 90% of the RSY (NR 90% RSY). Soil sampling was performed at 0-20 and 20-40 cm depths. Weak correlations were detected between anaerobic incubation and the SYC, and the hot KCl extractable N and phosphate-borate buffer at pH 11.2 extractable N with NUC. Methods did not correlate with RSY and the NR 90% RSY. No method is recommended for adjusting N fertilizer rates for application on sugarcane ratoons in the state of São Paulo, Brazil. To study the reactions of DON and mineral N, straw and soil samples were collected in the transition region between the two materials, in two experimental sites located in the State of São Paulo. The C mineralization and sorption of 14C-labelled amino acids mix, peptides, urea and protein was performed by addition of the compounds in straw and soil. The C mineralization and mineral N content by the addition of 14C-glucose with or without mineral N forms (NH4+-N and NO3--N) was also checked. There are marked differences between straw and soil regarding to the DON dynamics, microbial community profile and N immobilization. In general, the 14C remaining of the applied DON compounds in the soil was higher when compared to the straw. Peptides and urea had a rapid C mineralization, while the protein sorption was higher in the soil than the straw. The use of 14C-glucose with NO3--N intensified 14C mineralization in the straw of both sites. There was an intense immobilization of NH4+-N, mainly in the sugarcane residue.
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Predição da necessidade de fertilizante nitrogenado pela cana-de-açúcar e reações do nitrogênio orgânico e mineral dissolvidos em palha e solo de canaviais / Predicting nitrogen fertilizer needs for sugarcane and reactions of dissolved organic and mineral nitrogen in straw and soil from sugarcane fieldsEduardo Mariano 09 February 2015 (has links)
A recomendação de doses de nitrogênio (N) para a cana-de-açúcar (Saccharum spp.) com base em testes de solo é essencial para o aumento da sustentabilidade desse agroecossistema. Além disso, pouco se conhece sobre as reações do N orgânico dissolvido (NOD) na zona de transição palha-solo nos canaviais. A influência das formas minerais de N (N-NH4+ e N-NO3-) na mineralização de carbono (C) nessa região transitória também é desconhecida. Desse modo, os objetivos do estudo foram: i) correlacionar diversos métodos para a predição do N mineralizável do solo com parâmetros de resposta da cana-de-açúcar ao N; ii) quantificar os processos de mineralização de C e sorção de compostos do NOD aplicados em palha e solo (ambos amostrados na zona de transição); e iii) determinar a mineralização C e o conteúdo de N mineral em palha e solo de cana-de-açúcar (provenientes da zona de transição) pela adição de 14C-glicose associada ou não à fontes minerais de N. Entre 2006 e 2013 foram instalados 21 experimentos de curva de resposta da cana-de-açúcar ao N no Estado de São Paulo, Brasil, para correlacionar métodos de natureza biológica, química, microbiológica e isotópica (15N), com a produtividade de colmos (PCC) e extração de N (ENC) no tratamento controle, produção relativa da cultura (PRC) e com a dose de N necessária para obtenção de 90% da PRC (DN 90% PRC). As amostragens de solo foram realizadas nas camadas de 0-20 e 20-40 cm. Foram detectadas fracas correlações entre a incubação anaeróbia e a PCC, e o N extraível por KCl a quente por 4 h e o N extraível por tampão fosfato-borato a pH 11,2 com a ENC. Os métodos não se correlacionaram com a PRC e a DN 90% PRC. Nenhum método é recomendado no ajuste de doses de N para aplicação em soqueiras de cana-de-açúcar no Estado de São Paulo. Para o estudo das reações do NOD e do N mineral, amostras de palha e solo foram coletadas na região de transição entre os dois materiais, em dois sítios experimentais localizados no Estado de São Paulo. A mineralização de C e sorção de mistura de aminoácidos, peptídeos, ureia e proteína (todos marcados em 14C) foi determinada pela aplicação dos compostos em palha e solo. A mineralização de C e conteúdo de N mineral pela adição de 14C-glicose com ou sem as formas de N mineral (N-NH4+ e N-NO3-) também foi avaliada. Existem diferenças acentuadas entre a palha e solo relacionadas à dinâmica do NOD, perfil da comunidade microbiana e imobilização de N. Em geral, o conteúdo de 14C restante dos compostos do NOD foi maior no solo em relação à palha. Os peptídeos e a ureia apresentaram rápida mineralização de C, enquanto que a sorção da proteína foi maior no solo em comparação com a palha. A associação da 14C-glicose com N-NO3- resultou em maior mineralização de 14C na palha de ambos os sítios. Ocorreu intensa imobilização de N-NH4+, sobretudo no resíduo de cana-de-açúcar. / Recommendation of nitrogen (N) rates for sugarcane (Saccharum spp.) based upon soil testing is essential for increasing the sustainability of this agroecosystem. In addition, little is known about the dynamics of dissolved organic nitrogen (DON) in the straw-soil transition zone in sugarcane fields. The influence of mineral N forms in the carbon (C) mineralization in this transitional region is also unknown. Thus, the objectives of this study were: i) correlate several methods to predict the soil mineralizable N with sugarcane N response parameters; ii) quantifying the C mineralization and sorption processes of DON compounds applied to straw and soil (both sampled in the transition zone); and iii) determine the C mineralization and mineral N content in straw and soil (from the transition zone) by addition of 14C-glucose with or without mineral sources of N. Between 2006 and 2013, 21 sugarcane N response trials were performed in the State of São Paulo, Brazil, to correlate biological, chemical, microbiological and isotopic (15N) methods with stalks yield (SYC) and total N uptake (NUC) in the control treatment, relative stalks yield (RSY) and the N rate required to achieve 90% of the RSY (NR 90% RSY). Soil sampling was performed at 0-20 and 20-40 cm depths. Weak correlations were detected between anaerobic incubation and the SYC, and the hot KCl extractable N and phosphate-borate buffer at pH 11.2 extractable N with NUC. Methods did not correlate with RSY and the NR 90% RSY. No method is recommended for adjusting N fertilizer rates for application on sugarcane ratoons in the state of São Paulo, Brazil. To study the reactions of DON and mineral N, straw and soil samples were collected in the transition region between the two materials, in two experimental sites located in the State of São Paulo. The C mineralization and sorption of 14C-labelled amino acids mix, peptides, urea and protein was performed by addition of the compounds in straw and soil. The C mineralization and mineral N content by the addition of 14C-glucose with or without mineral N forms (NH4+-N and NO3--N) was also checked. There are marked differences between straw and soil regarding to the DON dynamics, microbial community profile and N immobilization. In general, the 14C remaining of the applied DON compounds in the soil was higher when compared to the straw. Peptides and urea had a rapid C mineralization, while the protein sorption was higher in the soil than the straw. The use of 14C-glucose with NO3--N intensified 14C mineralization in the straw of both sites. There was an intense immobilization of NH4+-N, mainly in the sugarcane residue.
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