Orientador: Altair Benedito Moreira / Coorientador: Ademir dos Santos / Banca: César Ricardo Teixeira Tarley / Banca: Eduardo Alves de Almeida / Resumo: Este trabalho teve como objetivo estudar a interações das Substâncias Húmicas (SH) com os metais cobre(II), cromo(III) e cromo(VI) por meio de dois métodos, o da supressão da fluorescência molecular e o sistema de ultrafiltração com fluxo tangencial (SUFT). As SH foram caracterizadas por técnicas espectroscópicas na região do infravermelho e do ultravioleta-visível e por fluorescência molecular. Foram realizadas duas coletas de sedimentos, uma no período de chuva e outra no de seca, sendo coletados em três rios da Bacia Hidrográfica do Turvo/Grande, Rio Preto, Rio Turvo e Rio Grande. O sedimento foi coletado com o auxilio de uma draga manual do tipo Van Veen. As SH foram extraídas de acordo com metodologia oficial sugerida pela Sociedade Internacional de Substâncias Húmicas (SISH). A constante de estabilidade condicional (Kc) foi determinada por meio da supressão da fluorescência e variou de 5,6x10-3 - 1,23 em período chuvoso para o íons cobre, e de 5,5x10-3 - 8,7x10-2 para o período de seca. Quando a Kc foi determinada para o complexo SH-Cr(III) valores de 1,9x10-1-5,2x10-1 e 2,1x10-1-3,5x10-1, foram determinados para o período de chuva e de seca, respectivamente. Por fim a Kc foi determinada para a interação das SH com Cr(VI), de forma geral os valores de Kc foram maiores para o período de chuva. A capacidade complexante (CC) determinada por meio do SUFT para a interação das SH com cobre(II) teve valores que variaram de 4,0x10-1 - 6,3x10-1 mmol Cu g-1 SH e de 1,4x10-1 - 5,3x10-1 mmol Cu g-1 SH para período de chuva e seca, respectivamente. Para o Cr(III) a CC variou de 2,1x10-1 - 9,7x10-1 e de 2,6x10-1 - 8,4x10-1 mmol Cr g-1 SH para o período de chuva e seca, respectivamente. Quando a interação das SH com o Cr(VI) foi estudada por meio do SUFT só foi possível calcular a CC para os pontos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work aimed to study the interactions of humic substances (HS) with copper(II), chromium(III) and chromium(VI), using by two methods, the suppression of the molecular fluorescence and tangential flow ultrafiltration sytem (TFUS). The HS were characterized by spectroscopic thecniques in the infrared and ultraviolet/visible region and molecular fluorescence. There were two sediment samples, one during the wet season and another the dry, being these sediments collected from the three Rivers of the Turvo/Grande drainage basin, Preto river, Turvo river and Grande river. The collection of sediment was carried out with the aid of a manual Van Veen type dredge. The HS were extracted according to the official methodology suggested by the International Humic Substances Society (IHSS). The conditional stability constant (Kc) was determined by suppressing fluorescence and ranged from 5,6x10-3 - 1,23 in the wet season for the copper ions, and of the 5,5x10-3 - 8,7x10-2 to the dry season. When Kc was determined for the complex HS-Cr(III) values of 1,9x10-1-5,2x10-1 e 2,1x10-1-3,5x10-1, were determined for the wet and dry seasons, respectively. Finally, the Kc was determined for the interactions oh HS with the Cr(VI) in geral the Kc values were higher for the wet season. Complexant capacity (CC) was determined by means of TFUS for the interactions of the HS with Copper(II) the values ranged from 4,0x10-1 - 6,3x10-1 mmol Cu g-1 HS and of 1,4x10-1 - 5,3x10-1 mmol Cu g-1 HS for a wet and dry season, respectively. For the Cr(III) CC ranged from 2,1x10-1 - 9,7x10-1 and from 2,6x10-1 - 8,4x10-1 mmol Cr g-1 HS for the wet and dry period, respectively. When the interactions oh HS with Cr(VI) was studied by means of TFUS was only possible to calculate the CC for the points NRP and CAPRP, as for others... (Complete abstract click electronic access below) / Mestre

O presente trabalho teve por objetivo estudar a resposta da cultura de melão conduzida em sistema orgânico a diferentes doses de substâncias húmicas extraídas de leonardita e esterco. Os tratamentos foram quatro doses de substâncias húmicas (0, 5, 10 e 20 mg.L-1 de solo) e esterco em combinação com dois biofertilizantes mais dois tratamentos adicionais utilizando fertilizantes convencionais com e sem esterco. O delineamento experimental foi em blocos ao acaso, com doze tratamentos e três repetições. Em função dos resultados obtidos, nas condições do experimento (solo com baixa CTC e baixo teor de matéria orgânica), pode-se concluir que: (i) a melhor resposta da cultura de melão (produtividade total e comercial, número de frutos comerciais e comprimento do fruto), conduzido em sistema orgânico de produção, na região de Petrolina-PE, é obtida com a adição de esterco; (ii) a produtividade total e comercial, o número total e comercial de frutos e a massa média de frutos de melão aumentaram com as doses de substâncias húmicas combinadas ao biofertilizante Agrobom; e (iii) não houve efeito da adição de esterco e das doses de substâncias húmicas, em combinação com caldas biofertilizantes aplicadas via fertirrigação na firmeza, na espessura da casca e no diâmetro da cavidade do fruto. / The present experiment had the aim of studying organic melon crop response to different rates of humic substances extracted from leonardite and manure. The treatments were four rates of humic substances (0, 5, 10 and 20 mg.L-1) and manure combined with two biofertilizers and two additional treatments using conventional fertilizers with and without manure. The experimental design was randomized complete blocks, with twelve treatments and three replications. The results (under similar soil conditions: low CEC and low organic matter content) allowed the following conclusions: (i) for all tested organic production systems, carried out at Petrolina, Pernambuco State (Brazil), the higher total and commercial yield, and the number and length of commercial melon fruits were obtained with manure addition; (ii) the higher rates of humic substances, combined with Agrobom biofertilizers, increased the total and commercial yield, the total and the commercial number and the mean mass of melon fruits; and (iii) there was no effect of manure addition and humic substances application (combined with two biofertilizers applied by fertigation) on the hardness, rind thickness and socket diameter of melon fruit.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2017-07-05T13:50:00Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese corrigida.pdf: 987397 bytes, checksum: 3971de521d0082be2abbdeb2af93354e (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-07-11T20:49:12Z (GMT) No. of bitstreams: 2 Tese corrigida.pdf: 987397 bytes, checksum: 3971de521d0082be2abbdeb2af93354e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-07-11T20:49:12Z (GMT). No. of bitstreams: 2 Tese corrigida.pdf: 987397 bytes, checksum: 3971de521d0082be2abbdeb2af93354e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-05-08 / O presente trabalho teve o objetivo de avaliar a produção de mudas de qualidade de duas cultivares de alface, 'Regina' e 'Mimosa Salad Bowl' roxa, com o uso de substratos alternativos a partir de sementes nua peletizada, nua e peletizada®. Foram conduzidos dois experimentos em casa de vegetação, com a cv. Regina em 2015 e com cv. Mimosa Salad Bowl roxa em 2016, onde foram avaliados sete substratos (T1-substrato comercial, T2-vermicomposto bovino (100%), T3- vermicomposto bovino (65%) + casca de arroz carbonizada (35%), T4- vermicomposto bovino (65%) + pinha moída (35%), T5-vermicomposto ovino (100%), T6-vermicomposto ovino (75%) + casca de arroz carbonizado (25%), T7- vermicomposto ovino (75%) + pinha moída (25%)) e três tipos de sementes ( nua peletizada com vermicomposto bovino, nua e peletizada®) . A semeadura foi feita em bandejas de poliestireno expandido com 128 células cada. O delineamento utilizado foi de blocos ao acaso com quatro repetições. Foram avaliados: índice de velocidade de emergência, diâmetro de colo, comprimento de raiz, altura da muda, massa fresca parte aérea e das raízes, massa seca parte aérea e das raízes, estabilidade do torrão, relação altura da muda/diâmetro de colo, índice de qualidade de Dickson e nitrogênio, potássio, fósforo, cálcio e magnésio da parte aérea das mudas. Observou-se com este estudo que: as misturas de vermicomposto bovino (65%) + casca de arroz carbonizada (35%) e vermicomposto bovino (65%) + pinha moída (35%) podem substituir o substrato comercial na produção de mudas de alface 'Mimosa Salad Bowl' roxa, enquanto que para 'Regina' a mistura vermicomposto bovino (65%) + casca de arroz carbonizada (35%) pode substituir o substrato comercial. O vermicomposto bovino favorece um aporte nutricional suficiente às mudas de alface cv. Regina e Mimosa Salad Bowl roxa produzidas através de sementes nuas peletizadas com vermicomposto bovino, nuas e peletizadas®. É viável a produção de mudas de alface 'Regina' e 'Mimosa Salad Bowl' roxa através de sementes nuas peletizadas com vermicomposto bovino. / The present work had the objective of evaluating the quality seedlings production of two lettuce cultivars, 'Regina' and 'Mimosa Salad Bowl' purple, with the use of alternative substrates from bare, pelleted and nude seeds. Two experiments were conducted in a greenhouse, ‘Regina’ in 2015 and ‘Mimosa Salad Bow’l purple in 2016, where seven substrates (T1-commercial substrate, T2-bovine manure vermicompost (100%), T3-bovine manure vermicompost (65%) + carbonized rice husk (35%), T4- bovine manure vermicompost 65%) + pine crushed (35%), T5-ovine manure vermicompost (100%), T6- ovine manure vermicompost (75%) + carbonized rice husk (25%), T7- ovine manure vermicompost (75%) + pine crushed (25%)) and three types of seeds (nude pelleted with bovine manure vermicompost, bare and pelletized). The sowing was done in trays of expanded polystyrene with 128 cells. The experimental design was a randomized block design with four replications. The following variables were evaluated: emergence velocity index, lap diameter, root length, seedling height, dry and fresh fitomass aerial and root, stability of the clod, height / height ratio, Dickson Quality Index and nitrogen, potassium, phosphorus, calcium and magnesium of the aerial part of the seedlings. It was observed in this study that: mixtures of bovine manure vermicompost (65%) + carbonized rice husk (35%) and bovine vermicompost (65%) + pine crushed (35%) can replace the commercial substrate in the production of seedlings Lettuce 'Mimosa Salad Bowl', while for 'Regina' bovine vermicompost (65%) + carbonized rice husk (35%) may replace the commercial substrate. The bovine manure vermicompost favors a sufficient nutritional contribution to lettuce seedlings ‘Regina’ and ‘Mimosa Salad Bowl’ purple produced through bare seed pellets with bovine manure vermicompost, bare and pelleted®. It is feasible to produce 'Regina' lettuce and 'Mimosa Salad Bowl' seedlings through bare seeds pelleted with bovine manure vermicompost.

Os solos tropicais altamente intemperizados apresentam elevada capacidade de adsorção de fósforo. Vários fatores podem influenciar a adsorção de P nestes solos, dentre eles destaca-se o teor de matéria orgânica. Os mecanismos envolvidos neste processo estão relacionados à liberação de ácidos orgânicos oriundos da decomposição da matéria orgânica, podendo ser de baixa massa molecular tais como, malato, oxalato ou citrato, ou de elevada massa molecular como ácidos húmicos e fúlvicos, que atuam na complexação do Fe ou Al em solução ou na superfície dos colóides, que por meio de troca de ligantes reduz assim a adsorção de P. O presente trabalho constou de quatro estudos, ambos realizados em casa-de-vegetação do Departamento de Ciência do Solo da ESALQ/USP, tendo como objetivos: (i) verificar o efeito da adição de ácidos orgânicos e fontes de substâncias húmicas, na disponibilidade de P em solos com diferentes capacidades de adsorção. Os tratamentos compreenderam 2 tipos de solo (Latossolo vermelho amarelo - LVA e LV), 2 fontes de P (Fosfato monocálcico - FMC p.a. e Fosfato natural reativo de Arad - FNR), 2 fontes de ácidos orgânicos de baixa massa molecular - AOBM (ácido cítrico - AC e ácido oxálico - AO), 2 fontes de substâncias húmicas (condicionador orgânico de solo - CO e turfa -TF)). As doses de AOBM foram de 0, 2, 4 e 8 mmol kg-1 e CO de 0, 150, 300, 600 L ha-1 e de TF 0, 20, 40, e 80 t ha-1; (ii) avaliar a eficiência agronômica de fontes de fósforo com solubilidade variável em água, com e sem adição de matéria orgânica. Os tratamentos constaram de 2 tipos de solo (LVA e LV), 2 fontes de P (Superfosfato triplo - SFT e Fosfato natural reativo - FNR), 3 doses de P (0, 50 e 100 mg kg-1 de P) e 3 doses de turfa - TF, correspondendo a 0, 25 e 50 t ha-1; (iii) avaliar o efeito da adição de fontes de substâncias húmicas na eficiência agronômica das fontes de P. Os tratamentos constaram de 2 solos (LVA e LV), 2 fontes de P (SFT e FNR) e 2 fontes de substâncias húmicas - FSH (CO e TF) e (iv) avaliar o efeito da adição e forma de aplicação de ácido cítrico na eficiência agronômica das fontes de P. O ácido cítrico (AC) foi adicionado nas doses de 0, 4 e 8 mmol kg-1 de AC, sendo as formas de aplicação avaliadas foram: (a) plantio (a dose completa de AC foi aplicada no plantio); (b) reposição = plantio + reposição (a dose completa de AC foi aplicada no plantio, sendo feito a reposição aos 7, 14, 21 e 28 dias de AC correspondendo a 50 % das doses iniciais; (c) parcelado (as doses de AC foram parceladas em 4 vezes). Os resultados obtidos permitem concluir que: a adição de ácidos orgânicos de baixa massa molecular e fontes de substâncias húmicas aumentou a disponibilidade de P, com maiores efeitos nos solos de baixa capacidade de adsorção de fósforo. O aumento da eficiência agronômica relativa após a adição de turfa foi maior para o fosfato natural reativo, quando comparado ao superfosfato triplo. A eficiência agronômica das fontes SFT e FNR é maior após a adição de condicionador orgânico a base de substâncias húmicas, quando comparado a adição de turfa. A eficiência agronômica relativa das fontes SFT e FNR é maior com a reposição do AC, quando compara a aplicação em dose única no plantio ou parcelado. / Tropical soils highly intemperized show increased capability on phosphorus (P) adsorption. Several factors may influence P adsorption in such soils, but special attention must be paid on the organic matter level. Mechanisms involved in this process are related to the release of organic acids derived from the decomposition of the organic matter, which may either have low molecular weight such as malic acids, oxalate and citrates; or may have high molecular weight such as humic and fulvic acids, that act in the complexation of ferric iron and aluminum either in solutions or on colloids surfaces, which, due to a shift of ligands, decrease P adsorption. This research work is comprised by four different studies, all of them performed under greenhouse conditions in the Department of Soil Sciences at ESALQ/USP, mainly aiming to: (i) verify the effect of the addition of organic acids and sources of humic substances on the availability of P in soils with different adsorption capacity. Treatments were performed in two types of soils (Red- Yellow Latosol LVA and LV), two sources of P (monocalcium phosphate - FMC p.a. - and Arad-reactive natural phosphate - FNR), 2 sources of low molecular weight organic acids - AOBM - (citric acid and oxalic acid) and 2 sources of humic substances (soil organic conditioner - CO - and peat - TF). Doses of AOBM were 0, 2, 4 and 8 mmol kg-1, doses of CO were 0, 150, 300 and 600 L ha-1 and doses of TF were 0, 20, 40 and 80 t ha-1; (ii) evaluate the agronomic efficiency of phosphorus sources with variable water solubility, with and without the addition of organic matter. Treatments consisted of two kinds of soils (LVA and LV), two sources of P (triple superphosphate - SFT - and reactive natural phosphate - FNR), three doses of P (0, 50 and 100 mg kg-1) and three doses of peat, corresponding to 0, 25 and 50 t ha-1; (iii) evaluate the effect of the addition of humic substances sources on the agronomic efficiency of P sources. Treatments consisted of 2 soils (LVA e LV), 2 sources of P (SFT and FNR) and 2 sources of humic substances - FSH (CO and TF); and (iv) evaluate the effect of the addition and the way of application of citric acid on the agronomic efficiency of P sources. Citric acid was added in doses corresponding to 0, 4 and 8 mmol kg-1 AC, and exposure methods assessed were: (a) planting (full AC dose applied during planting); (b) reposition = planting + reposition (full AC dose was applied during planting, with the reposition of AC on the 7th, 14th, 21st and 28th day corresponding to 50% of initials doses; (c) partitioned (AC doses were partitioned in four times). Results obtained allowed us to conclude that the addition of low molecular weight organic acids and humic substances sources increased the availability of P, with grater effects in soils of low capacity of P adsorption. The increase on relative agronomic efficiency after the addition of peat was higher for reactive natural phosphate, when compared to triple superphosphate. Agronomic efficiency of SFT and FNR sources is higher when compared to peat addition. Relative agronomic efficiency of SFT and FNR sources was higher with the repositioning of AC, when compared to the exposure to a single dose during planting or partitioned.

Os solos tropicais altamente intemperizados apresentam elevada capacidade de adsorção de fósforo. Vários fatores podem influenciar a adsorção de P nestes solos, dentre eles destaca-se o teor de matéria orgânica. Os mecanismos envolvidos neste processo estão relacionados à liberação de ácidos orgânicos oriundos da decomposição da matéria orgânica, podendo ser de baixa massa molecular tais como, malato, oxalato ou citrato, ou de elevada massa molecular como ácidos húmicos e fúlvicos, que atuam na complexação do Fe ou Al em solução ou na superfície dos colóides, que por meio de troca de ligantes reduz assim a adsorção de P. O presente trabalho constou de quatro estudos, ambos realizados em casa-de-vegetação do Departamento de Ciência do Solo da ESALQ/USP, tendo como objetivos: (i) verificar o efeito da adição de ácidos orgânicos e fontes de substâncias húmicas, na disponibilidade de P em solos com diferentes capacidades de adsorção. Os tratamentos compreenderam 2 tipos de solo (Latossolo vermelho amarelo - LVA e LV), 2 fontes de P (Fosfato monocálcico - FMC p.a. e Fosfato natural reativo de Arad - FNR), 2 fontes de ácidos orgânicos de baixa massa molecular - AOBM (ácido cítrico - AC e ácido oxálico - AO), 2 fontes de substâncias húmicas (condicionador orgânico de solo - CO e turfa -TF)). As doses de AOBM foram de 0, 2, 4 e 8 mmol kg-1 e CO de 0, 150, 300, 600 L ha-1 e de TF 0, 20, 40, e 80 t ha-1; (ii) avaliar a eficiência agronômica de fontes de fósforo com solubilidade variável em água, com e sem adição de matéria orgânica. Os tratamentos constaram de 2 tipos de solo (LVA e LV), 2 fontes de P (Superfosfato triplo - SFT e Fosfato natural reativo - FNR), 3 doses de P (0, 50 e 100 mg kg-1 de P) e 3 doses de turfa - TF, correspondendo a 0, 25 e 50 t ha-1; (iii) avaliar o efeito da adição de fontes de substâncias húmicas na eficiência agronômica das fontes de P. Os tratamentos constaram de 2 solos (LVA e LV), 2 fontes de P (SFT e FNR) e 2 fontes de substâncias húmicas - FSH (CO e TF) e (iv) avaliar o efeito da adição e forma de aplicação de ácido cítrico na eficiência agronômica das fontes de P. O ácido cítrico (AC) foi adicionado nas doses de 0, 4 e 8 mmol kg-1 de AC, sendo as formas de aplicação avaliadas foram: (a) plantio (a dose completa de AC foi aplicada no plantio); (b) reposição = plantio + reposição (a dose completa de AC foi aplicada no plantio, sendo feito a reposição aos 7, 14, 21 e 28 dias de AC correspondendo a 50 % das doses iniciais; (c) parcelado (as doses de AC foram parceladas em 4 vezes). Os resultados obtidos permitem concluir que: a adição de ácidos orgânicos de baixa massa molecular e fontes de substâncias húmicas aumentou a disponibilidade de P, com maiores efeitos nos solos de baixa capacidade de adsorção de fósforo. O aumento da eficiência agronômica relativa após a adição de turfa foi maior para o fosfato natural reativo, quando comparado ao superfosfato triplo. A eficiência agronômica das fontes SFT e FNR é maior após a adição de condicionador orgânico a base de substâncias húmicas, quando comparado a adição de turfa. A eficiência agronômica relativa das fontes SFT e FNR é maior com a reposição do AC, quando compara a aplicação em dose única no plantio ou parcelado. / Tropical soils highly intemperized show increased capability on phosphorus (P) adsorption. Several factors may influence P adsorption in such soils, but special attention must be paid on the organic matter level. Mechanisms involved in this process are related to the release of organic acids derived from the decomposition of the organic matter, which may either have low molecular weight such as malic acids, oxalate and citrates; or may have high molecular weight such as humic and fulvic acids, that act in the complexation of ferric iron and aluminum either in solutions or on colloids surfaces, which, due to a shift of ligands, decrease P adsorption. This research work is comprised by four different studies, all of them performed under greenhouse conditions in the Department of Soil Sciences at ESALQ/USP, mainly aiming to: (i) verify the effect of the addition of organic acids and sources of humic substances on the availability of P in soils with different adsorption capacity. Treatments were performed in two types of soils (Red- Yellow Latosol LVA and LV), two sources of P (monocalcium phosphate - FMC p.a. - and Arad-reactive natural phosphate - FNR), 2 sources of low molecular weight organic acids - AOBM - (citric acid and oxalic acid) and 2 sources of humic substances (soil organic conditioner - CO - and peat - TF). Doses of AOBM were 0, 2, 4 and 8 mmol kg-1, doses of CO were 0, 150, 300 and 600 L ha-1 and doses of TF were 0, 20, 40 and 80 t ha-1; (ii) evaluate the agronomic efficiency of phosphorus sources with variable water solubility, with and without the addition of organic matter. Treatments consisted of two kinds of soils (LVA and LV), two sources of P (triple superphosphate - SFT - and reactive natural phosphate - FNR), three doses of P (0, 50 and 100 mg kg-1) and three doses of peat, corresponding to 0, 25 and 50 t ha-1; (iii) evaluate the effect of the addition of humic substances sources on the agronomic efficiency of P sources. Treatments consisted of 2 soils (LVA e LV), 2 sources of P (SFT and FNR) and 2 sources of humic substances - FSH (CO and TF); and (iv) evaluate the effect of the addition and the way of application of citric acid on the agronomic efficiency of P sources. Citric acid was added in doses corresponding to 0, 4 and 8 mmol kg-1 AC, and exposure methods assessed were: (a) planting (full AC dose applied during planting); (b) reposition = planting + reposition (full AC dose was applied during planting, with the reposition of AC on the 7th, 14th, 21st and 28th day corresponding to 50% of initials doses; (c) partitioned (AC doses were partitioned in four times). Results obtained allowed us to conclude that the addition of low molecular weight organic acids and humic substances sources increased the availability of P, with grater effects in soils of low capacity of P adsorption. The increase on relative agronomic efficiency after the addition of peat was higher for reactive natural phosphate, when compared to triple superphosphate. Agronomic efficiency of SFT and FNR sources is higher when compared to peat addition. Relative agronomic efficiency of SFT and FNR sources was higher with the repositioning of AC, when compared to the exposure to a single dose during planting or partitioned.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 157-170).

Bibliography: leaves 164-193. This study aims to quantify the belowground input of organic carbon by barrel medic using techniques that account for root death and decomposition as well as root secretion and exudation. It also investigates the effect of defoliation on carbon allocation within the plant so as to determine the potential for optimising carbon input to the soil through grazing management.

Bibliography: leaves 134-148. The objectives of this study are to determine if and how inorganic matrices influence organic matter decomposition with particular emphasis on the biochemical changes which occur as decomposition progresses. The influence of inorganic matrices (sand, sand + kaolin and loamy sand) on the decomposition of straw and Eucalyptus litter during incubations was followed by various chemical and spectroscopic methods to aid in the understanding of the mechanism of physical protection of organic matter in soils.

In der vorliegenden Arbeit wurde eine von der Sächsischen Landesanstalt für Landwirtschaft (KOLBE 2006) entwickelte standortangepasste Methode zur Humusbilanzierung an sächsischen Dauertestflächen getestet. Ziel der Arbeit war es, die Anwendbarkeit der Methode in einem relativ großen, standörtlich stark differenzierten Gebiet wie Sachsen zu beurteilen und die Ergebnisse den Bilanzergebnissen anderer Humusbilanzmethoden (VDLUFA-Methode und REPRO) gegenüberzustellen und sie zu vergleichen. Bei dem Vergleich wurden die Unterschiede zwischen konventioneller und ökologischer Landbewirtschaftung berücksichtigt. Mit den ermittelten Ergebnissen für die Humusbilanzierung konnte die mögliche Abfuhr organischer Reststoffe der Landwirtschaft von den Ackerflächen Sachsens kalkuliert werden. Die Ergebnisse der Arbeit werden intensiv unter den Schlagworten Erhalt der Bodenfruchtbarkeit, Erweiterung der Produktionsflächen für nachwachsende Rohstoffe und Klimawandel diskutiert.

The effects of increasing periods under sugarcane monoculture (managed by preharvest burning) on soil organic matter content and related soil properties were investigated in the 0 to 10 cm layer of a sandy coastal Ochric Cambisol (Glenrosa soils) and a red Rhodic Ferralsol (Hutton soil) from the sugar belt of KwaZulu-Natal. The organic C content at both sites under undisturbed vegetation is about 48 g C kg-I. This declined exponentially with increasing years under sugarcane. For the Glenrosa site, organic C reached a new equilibrium level of about 20 g kg-I while at the Hutton soil the equivalent value was 41 g kg-I. The higher organic matter content maintained at the Hutton site was attributed mainly to clay protection of organic matter since the clay content of the Hutton soil was 61 % compared to the 18 % for the Glenrosa soil. The loss of soil organic matter under sugarcane resulted in a concomitant decline in soil microbial biomass C, microbial quotient, basal respiration, aggregate stability, arylsulphatase and acid phosphatase activity. The activities of arylsulphatase and acid phosphatase like those for concentrations of microbial biomass and organic C, were higher for the Hutton than Glenrosa soils. At the Glenrosa site, the natural OBC abundance in soils was used to calculate the loss offorest-derived, native soil C and the concomitant input of sugarcane-derived C. Sugarcane-derived C increased over time until it accounted for about 61 % of organic C in the surface 10 cm in soils that had been under sugarcane for greater than 50 years. The effects of agricultural land use (including burnt sugarcane) on organic matter content and related soil properties were compared with those under undisturbed native grassland in KwaZulu-Natal. Two separate farms situated on Oxisols were used and both contained fields with continuous long-term (>20 years) cropping histories. At site 1, soil organic C content in the surface 10 cm followed the order permanent kikuyu pasture> annual ryegrass pasture> native grassland> preharvest burnt sugarcane > maize under conventional tillage (CT). At site 2, organic C in the surface 20 cm decreased in the general order kikuyu pasture> native grassland > annual ryegrass pasture> maize under zero tillage (ZT) ~ maize (CT). Organic C, microbial biomass C, microbial quotient, basal respiration and aggregate stability were substantially greater in the surface 5 cm under maize ZT than maize CT. In the undisturbed sites (eg native grassland and kikuyu pasture) the metabolic quotient increased with depth. By contrast under maize CT and sugarcane there was no significant stratification of organic C, yet there was a sharp decrease in metabolic quotient with depth. Aggregate stability was high under both native grassland and kikuyu pasture and it remained high to 40 cm depth under the deep-rooted kikuyu pasture. Although soil organic C was similar under maize CT and sugarcane, values for microbial biomass C, microbial quotient, basal respiration and aggregate stability were lower, and those for metabolic quotient and bulk density were higher, under sugarcane. This was attributed to the fallow nature of the soil in the interrows of sugarcane fields. It was concluded that the loss of soil organic matter, microbial activity and aggregate stability is potentially problematic under maize CT and sugarcane and measures to improve organic matter status should be considered. For sugarcane, this could include green cane harvesting and the use of green manure crops in rotation. / Thesis (M.Sc.)- University of Natal, Pietermaritzburg, 2002.