3 pp. / Gypsum can help stabilize aggregate structure in some soils.

Revised; Originally Published 2006 / 5 pp.

Mycorrhizae improve plant growth and ecosystem sustainability by forming a symbiotic association with higher plants including the economically important willows (Salix spp.). With the recognition of the importance of mycorrhizae in terrestrial ecosystems, inoculation of plants with mycorrhizae is becoming a common practice in agricultural and land reclamation industries. However, little information is available on important ecological parameters such as soil aggregation, soil organic carbon content (SOC) and mycorrhizal communities associated with willow rhizospheres in response to mycorrhizal inoculation in willow systems. The main objectives of this research were to explore how commercial mycorrhizal inoculation of willows impacts (1) percent water-stable soil aggregates (%WSA); (2) indigenous arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) community composition associated with different size soil aggregates; (3) SOC, and (4) willow growth. These objectives were examined under both greenhouse and field conditions. Using molecular approaches, we observed the existence of spatial variability in indigenous AMF communities among different soil aggregate size classes. This spatial variability varied with type of soil and could be reduced by inoculating with a commercial AMF inoculant. The indigenous EMF diversity was low and did not show spatial heterogeneity among soil aggregates, but it did vary with soil type. In addition, other parameters, including %WSA, SOC within the willow rhizosphere, and willow plant growth also varied by soil type and changed in association with commercial mycorrhizal inoculation. In the field experiment, soil extracts from willow nursery soil had comparable plant growth promotion with commercial mycorrhizal inoculation, and altered the AMF community associated with bulk soil and soil aggregates in the willow rhizosphere. These results suggest that historically superior willow growth in the willow nursery soil could be due to pre-existing soil microbiological factors. Overall this research indicates that AMF and EMF inoculation has the potential to influence the composition of the AMF community, but had little influence on the composition of the EMF community in the systems tested. / Natural Sciences and Engineering Research Council of Canada

The Kentucky Division of Water indicates that agriculture is responsible for 55% of the Commonwealth’s assessed streams not supporting their designated uses. Riparian buffers reduce nonpoint source pollution in agroecosystems by storing and cycling nutrients, stabilizing streambanks, increasing infiltration, and storing water. Specific information regarding riparian buffer management is needed for land managers to maximize buffer effectiveness at reducing agricultural contaminants impairing water quality. Baseline soil properties (texture, pH, C and nutrients) of the riparian buffer surrounding a tributary of Cane Run Creek in Fayette County, KY were characterized prior to imposing three mowing regimes (intense, moderate, and no mow treatments) and one native grass regime. Measurements were made along parallel transects located 2-m and 8-m distances from the stream. Root biomass, aggregate distribution, and saturated hydraulic conductivity were measured along the 2-m transect in two consecutive years following treatment establishment. The 2-m transect soils had the highest C, pH, Ca, Zn, and sand content. The 8-m transect had the highest P, K, Mg, and clay content. Semivariogram analysis of C content indicated slight to moderate spatial dependency along the 2m transect and moderate to strong spatial dependency along the 8m transect. Root biomass increased with decreased mowing frequency at the surface depth after one year; the native grass treatment had significantly less root biomass in both years compared to mowing treatments. There was no significant treatment effect on aggregate size distribution at the surface depth in either year. Mean weight diameter and large macroaggregates decreased from 2011 to 2012. Vegetation treatment had no statistically significant effect on water stable aggregates or saturated hydraulic conductivity. Experimental semivariograms provided evidence of spatial structure at multiple scales in root biomass, aggregates, and soil C. Spatial variability occurred over a shorter lag distance in 2012 than 2011, suggesting an effect of imposed treatments slowly developing over time. This study provides important insights on riparian buffer soil properties, soil sampling strategies to detect spatial variability in riparian buffers, and length of time needed to assess effects of vegetation management regimes on riparian root biomass, soil aggregates, and hydraulic conductivity.

Dissolved organic carbon (DOC) plays an important role in the global carbon (C) cycle because increases in aqueous C potentially contribute to rising atmospheric CO2 levels. Over the past few decades, headwater streams of the northern hemisphere have shown increased amounts of DOC coinciding with decreased acid deposition. Although the issue is widely discussed in the literature, a mechanistic link between precipitation composition and stream water DOC has not yet been proposed. In this study, the breakup of soil aggregates is hypothesized as the mechanistic link between reduced acid deposition and DOC increases in surface waters. Specific hypotheses state that soil aggregate dispersion (and the ensuing release of DOC from these aggregates) is driven by a decrease in soil solution ionic strength (IS, decreasing the tendency of flocculation) as well as a shift from divalent to monovalent cations (reducing the propensity for cation bridging) in soil solution. These hypotheses were tested on soil samples collected from several riparian zone and hillslope positions along three flagged transects in the acid-impacted Sleepers River Research Watershed in northeastern Vermont. To determine soil C content by landscape position, samples from transects spanning hilltop to hillslope and riparian area, as well as replicated hillslope and riparian samples (n=40) were analyzed. Aqueous soil extracts simulate the flushing of soils during hydrologic events (e.g. rain or snowmelt) and were used to test the effect of soil solution chemistry on DOC release. Extracts were prepared with solutions of varying IS (0-0.005M) and composition (CaCl2 and NaCl) on replicated soil samples (n=54) and changes in DOC release and aggregate size were monitored. As IS of the extraction solution increased, the amount of DOC in solution decreased, and aggregate size increased. This was presumably due to cations bridging and diffuse double layer effects. This effect was reversed in low ionic strength solutions where DOC release was significantly higher and average aggregate size was smaller. While extraction solution controlled the amount of C liberated, landscape position impacted the quality, but not quantity, of released DOC. This study is the first to propose a mechanistic link observed changes in DOC in surface waters and recovery from acidification and provides initial experimental evidence that soil aggregates indeed play a role in the generation of DOC.

The primary objective of this research was to develop a landscape-oriented, process-based approach that can enhance understanding and prediction of SOC fluxes in IMLs by incorporating the key mechanisms impacting soil carbon dynamics when moving from the soilscape to the landscape. The mechanisms that are considered to be the focus of this study are redistribution of SOC due to erosion and deposition without neglecting the importance of litter incorporation into the soil column, decomposition due to microbial activity, and physical and chemical stabilization of carbon. To accomplish this objective, field experiments were performed to examine how selective entrainment of different soil size fractions, quantified through the enrichment ratio (ER), varies with management and hillslope position. Differential modes in soil mobilization between rill and interrill areas were either elevated or dampened depending on the prevalent management practice, the gradient of the site and landscape position. Sites where sediment and runoff fluxes were highest were found to have lower ER values (around unity) due to the mobilization of all size classes making static and dynamic samples almost identical. The size fractions analyzed in these experiments were found to have varying levels of carbon associated with them, especially the larger aggregates, which encapsulate organic material. Neglecting them in transport estimates could lead to large errors in predicted fluxes of SOC. For this reason, a careful attention was placed on identifying how aggregate stability varies with respect to management and hillslope position, through controlled experiments looking size distributions to reflect tillage disturbance and aggregate stability to assess resistance to rainsplash. Lastly, a landscape-oriented modeling framework was developed that captures not only the SOC spatial heterogeneity in IMLs but also determines the impacts that redistribution has on this heterogeneity and ultimately on SOC dynamics. The integrative modeling framework considers the collective effects of both rainsplash/rainfall- and tillage-induced erosion on SOC redistribution in IMLs through an ER-module developed and woven within this framework to connect an upland erosion model with a soil biogeochemical model. It provides not only size fraction updates to the active layer and ER values, but also explicitly considers the effects of splash-driven interrill erosion on those ER estimates. The model was applied to twentieth-century changes in SOC across a representative agricultural hillslope in the study watershed and compared to recent SOC data. The chronosequence in SOC storage within the erosional zone revealed that soils were continually depleted of the rich organic matter long after the 1930’s “Dust bowl” due to enhanced erosion that accompanied agricultural practices. However, conservation tillage and enhanced crop production that began in the late 1980’s reversed the downward trend in SOC losses, causing nearly 26% of the lost SOC to be regained. Results from this study can be used to aid policy and decision makers in developing a food-system that accounts for the co-evolution of human and natural activity, to develop sustainable agro-ecosystems through the use of data supported recommended best management practices.

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Made available in DSpace on 2017-07-21T19:25:53Z (GMT). No. of bitstreams: 1 Rosilene dos Santos.pdf: 3301508 bytes, checksum: 9f8d75d471a6d96f42a2fa59a3733772 (MD5) Previous issue date: 2008-01-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / It has been unquestionable the importance of the studies and researches that seek for the understanding of the physical and hydraulic properties of the soil and that these studies and researches try to correlate them with the soil physical attributes. This work presents the use of the methodology presented in Leeds-Harrison et al. (1994), developed for the determination of the saturated hydraulic conductivity at the level of aggregates of the soil and the use of Permeâmetro of Guelph for measures of that property in field.. In this work the aggregates of the soil were investigated submitted to systems conventional tillage and direct tillage. To correlate the hydraulic conductivity of the soil with its retention properties, the retention curves and distribution of pores of the aggregate near the saturation condition they were done through a system based on the idea of a funnel of porous plate or funnel of Haines. Measures of the bulk density, total porosity, macroporosity and microporosity of the investigated aggregates were also accomplished. The obtained results showed that the conventional tillage presented larger value of the saturated hydraulic conductivity on average compared with the direct tillage, so much in field conditions as in the form of aggregates. The direct tillage presented a capacity of larger retention compared to the conventional tillage. This can be due to the largest amount of microporous found in this tillage type. The pores distribution curves shows on average a larger amount of smaller pores in the aggregates of the direct tillage, what might have determined its smallest value of hydraulic conductivity in relation to the conventional tillage. The tillage type can propitiate the formation of pores with larger diameters, in which, firstly, allow larger values of saturated hydraulic conductivity. However, due to the no structures imposed to the soil samples, nothing can be affirmed in regard to the continuity of these types of pores. / É indiscutível a importância de estudos e pesquisas que visam o entendimento das propriedades físicas e hídricas do solo e de que tentem correlacioná-las com seus atributos físicos. Este trabalho apresenta a utilização da metodologia apresentada em Leeds-Harrison & Youngs (1997), desenvolvida para a determinação da condutividade hidráulica saturada ao nível de agregados de solo e o uso do Permeâmetro de Guelph para medidas dessa propriedade em campo. Nesta pesquisa foram investigados agregados de solo submetidos aos sistemas de plantio convencional e direto. Para correlacionar a condutividade hidráulica do solo com suas propriedades de retenção, as curvas de retenção e de distribuição de poros dos agregados próximos à condição de saturação foram feita através de um sistema baseado na idéia de um funil de placa porosa ou funil de Haines. Também foram realizadas medidas da densidade global, porosidade total, macroporosidade e microporosidade dos agregados investigados. Os resultados obtidos mostraram que o plantio convencional apresentou em média maior valor da condutividade hidráulica saturada comparada com o plantio direto, tanto em condições de campo como na forma de agregados. O plantio direto apresentou uma capacidade de retenção maior comparada com o plantio convencional. Isto pode ser devido ao maior número de microporos encontrados neste tipo de plantio. As curvas de distribuição de poros mostram em média um número maior de poros menores nos agregados do plantio direto, o que pode ter determinado seu menor valor de condutividade hidráulica em relação ao plantio convencional. O tipo de manejo pode propiciar a formação de poros com diâmetros maiores, os quais, em princípio, permitem maiores valores de condutividade hidráulica saturada. No entanto, devido às desestruturações impostas às amostras de solo, nada se pode afirmar a respeito da continuidade desses tipos de poros.

Submitted by Afonso Peche Filho (afonsopeche@gmail.com) on 2018-07-03T20:08:00Z No. of bitstreams: 1 Tese afonso final.pdf: 4978260 bytes, checksum: 84862d61e159e422ffd012fcbd059f87 (MD5) / Approved for entry into archive by Bruna Bacalgini null (bruna@sorocaba.unesp.br) on 2018-07-04T16:43:48Z (GMT) No. of bitstreams: 1 pechefilho_a_dr_soro.pdf: 4978260 bytes, checksum: 84862d61e159e422ffd012fcbd059f87 (MD5) / Made available in DSpace on 2018-07-04T16:43:48Z (GMT). No. of bitstreams: 1 pechefilho_a_dr_soro.pdf: 4978260 bytes, checksum: 84862d61e159e422ffd012fcbd059f87 (MD5) Previous issue date: 2018-03-02 / As questões ambientais que envolvem os efeitos do manejo e da degradação do solo necessitam de forma acelerada de pesquisa e muita extensão. Novos saberes e conhecimentos têm alcançado parte da comunidade acadêmica, mas ainda está aquém das necessidades para técnicos e leigos envolvidos em trazer soluções para problemas da ocupação, uso e degradação das terras. O manejo e recuperação ambiental de áreas degradadas são complexos e requerem diferentes tecnologias para o diagnóstico e avaliação. O uso de indicadores como diâmetro médio geométrico e distribuição percentual de agregado são parâmetros de uso consolidados, mas trazem limitações para questões complexas como o diagnostico do estado e condição de agregação do solo. A agregação do solo vem sendo estudada desde o inicio do século passado, mas são poucos os avanços conseguidos em popularizar a analise de agregação do solo agrícola como uma ferramenta laboratorial e prática. Além de que, falta conhecimento para popularizar a condição de agregação como informação de uso corrente. O uso de imagens obtidas e processadas em alta resolução permite sua aplicação em diferentes ramos da ciência, podendo ser aplicada nos estudos relacionados com o processo de agregação permitindo viabilizar o mais conhecimento ao processo. Este trabalho tem como objetivo desenvolver uma proposta metodológica para determinar a condição da qualidade de agregação, com base na tipificação de agregados e nos efeitos da variabilidade de composição em amostras de solo agrícola. Foram utilizados parâmetros relacionados com a forma, superfície e biogênese de agregados como indicadores de variabilidade da agregação do solo em duas amostras de latossolo vermelho de textura média, sendo que uma delas é referente a uma parcela de solo que recebeu um produto fertilizante/agregante Microgeo® e outra parcela sem ter recebido o produto. A obtenção dos agregados foi através do processo de peneiramento via seca utilizando cinco peneiras de diferentes calibres. A análise de agregados foi realizada em laboratório a partir de uma sub-amostra contendo 100 agregados oriundos de cada peneira específica, totalizando 500 agregados por amostras individuais de solo, perfazendo um total de 1000 agregados avaliados. A partir da obtenção de 1000 imagens fotográficas, com auxílio de um programa de processamento de imagens, obtêm-se um banco de dados referentes aos parâmetros morfométricos. Através do uso de tecnologia Fuzzy obteve-se um banco de dados numéricos referente à tipificação com base na análise visual da forma, superfície e biogênese dos agregados. Para cada conjunto de dados foi elaborado uma representação gráfica da variabilidade e seu respectivo quadro analítico descritivo. Com auxílio de medidas separatrizes do tipo quintis os dados foram classificados de acordo com a tipologia de ocorrência. Foram utilizados como parâmetros morfométricos o “diâmetro de Feret”, e como parâmetro de tipificação rugosidade de superfície e a “saída Fuzzy de tipificação” (os valores de integração com uso da tecnologia Fuzzy) o qual denominamos “Indicie Fuzzy de Tipificação”. Os resultados permitem afirmar que o trabalho atendeu os objetivos proposto de oferecer para sociedade uma “metodologia para qualificar a agregação em amostras de solos agrícolas”. Os resultados permitem aceitar as hipóteses formuladas e concluir que o estudo sobre efeitos da variabilidade permite quantificar, diagnosticar e qualificar o estado de agregação de amostras de solo. / Environmental issues involving the soil management effects and degradation are increasing and need to be extensively researched to be managed. New knowledge about solutions has been produced by academic research, but is still insufficient to solve the problems faced by technicians and other people involved to the field land use planning and degradation problems. Furthermore, the management of soil quality and land reclamation is complex, requiring different technologies for diagnosis and evaluation. The use of indicators, such as geometric mean diameter and percentage distribution of aggregate size, represents classical approaches, but both have limitations in treating the complexity of soil aggregation process. The soil aggregation has been studied since the beginning of the last century, but few advances have been made to popularize it to analyze agricultural soil quality. There are several difficulties to develop laboratory routines and practical tool to evaluate it. The use and processing of high resolution images have been widely applied in several fields of science and represents an interesting solution to study soil aggregation. To fill the existing gap, this works presents a methodological proposal to assess the quality of soil aggregation, by a classification of soil aggregates in terms of composition and variability. Agricultural soil aggregates were analyzed by three attributes: shape, surface and biogenesis. These parameters were used as indicators of soil aggregation quality, and the variability on each parameter was evaluates for two samples of medium texture red latosol, one of them referring to a plot of soil that received a fertilizer/aggregate product Microgeo® and another without receiving it. The aggregates were passed through the dry sieving process using five different sizes. The laboratorial analysis was performed by subsampling 100 aggregates from each sieve, totaling 500 aggregates per soil samples, and making a total of 1000 aggregates. Each soil aggregate was photographed, totalling1000 pictures, later processed on ImageJ. All results were organized in a database, containing information about the morphometric parameters of all soil aggregates. Fuzzy Logic was employed to transform the aggregate type into numeric values, using the visual analysis of the shape, surface and biogenesis. For each data set, a graphical representation of the variability and its descriptive statistics were calculated, producing an analytical framework. Statistical measures were used to classify the samples according to occurrence of aggregate type. To classify the samples and two sets of indexes were developed. The first one was based on the "Feret diameter", used as morphometric indicator, and the second one based on the "Fuzzy typing output", index produced by the integration of the values of shape, surface and biogenesis by a Fuzzy Inference System, which we call "Fuzzy index of typing". These results allowed affirming that the work fulfill the proposed objectives, offering to society a "methodology to qualify the aggregation quality in samples of agricultural soils". The results also allowed us to accept the formulated hypotheses and conclude that the study of variability can be used to quantify, diagnose and qualify the state of aggregation of soil samples.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The sugarcane crop is the major agricultural activity in the coastal tableland ecosystems in Alagoas State, exerting a remarkable influence in the economical and social aspects. This activity has been continuously and intensively conducted for several years and the necessity of environmental conservation and preservation of the several natural resources in this agroecosystem makes the adoption of sustainable practices mandatory for this activity. Among these resources, soil assumes a primary role and the evaluation of its quality through the observation and analysis of physical, chemical and biological indicators that are sensitive to management practices and robust to seasonal variations may be used to define this agroecosystem sustainability. Therefore, the objective of this work was to select indicator variables of soil conservation that fulfill the criteria of sensitivity to management and robustness to seasonal variability. For this, ten composite soil samples (0-10 cm) were taken from areas grown with organic sugarcane (OS), unburned sugarcane (US), and burned sugarcane (BS), as well as from an adjacent native forest (NF) used as a reference of the undisturbed condition. Sampling was carried out at two dates: July 2005 (rainy season) and March 2006 (dry season). The following variables were analyzed: microbial biomass-C (MBC), total organic C (TOC), soil enzyme activity by the fluorescein diacetate (FDA) hydrolysis technique, the weighed mean diameter of water stable soil aggregates (WSA), and the percent of macroaggregates (PMA). MBC and TOC were higher in NF than in the cultivated areas. No differences were observed in these C pools between the three sugarcane management treatments. The response of FDA to the crop management was dependent on the sampling time. In the rainy period, the activity followed the order: NF > OS > US > BS; in the dry season, only NF differed from the other treatments. Irrespective to the sampling time, WSA and PMA decreased according with the order NF > OS = US > BS. The variables WSA and PMA were quite sensitive to discriminate between sugarcane managements, and, at the same time, robust to seasonal variations. As an additional study, we analyzed the distribution of enzyme activity (fluorescein diacetate hydrolisys) across different diameter classes of water stable aggregates in soil samples from NF and US in order to verify the relationship between these variables. It was suggested the occurrence of two pools of fluorescein diacetate catalyzing enzymes in soils from NF and US. A non-monotonic relationship was observed between aggregate diameter and FDA. For both soils, intermediate aggregate size classes (0.25 to 1.00 mm) had lower FDA values than the classes bellow and above this diameter range. / No ecossistema dos tabuleiros costeiros do Estado de Alagoas a cultura da cana-deaçúcar destaca-se como a principal atividade agrícola exercendo influência nos aspectos econômico e ambiental da região. Esta atividade tem sido praticada de forma contínua e intensa ao longo do tempo e a necessidade de conservação ambiental e preservação dos diversos recursos presentes neste agroecossistema têm exigido que a sua utilização seja sustentável. Entre os recursos existentes, o solo assume papel importante e a avaliação da sua qualidade através da observação e análise dos indicadores físicos, químicos e biológicos do solo que sejam sensíveis às práticas de manejo e resistentes a variações sazonais podem ser utilizadas para definir a sustentabilidade deste agroecossistema. Assim o objetivo deste trabalho foi selecionar variáveis indicadoras de conservação do solo que atendam aos critérios de sensibilidade ao manejo e robustez as variações sazonais. Para tanto, dez amostras compostas de solo (0-10 cm) foram coletadas de áreas sob cana-orgânica (CO), cana-crua (CC), e cana-queimada (CQ), bem como de uma mata nativa (MN) adjacente usada como referência da condição não-manejada. A amostragem foi realizada em duas datas: julho de 2005 (chuva) e março de 2006 (seca). Avaliaram-se o C da biomassa microbiana (CBM), o C orgânico total (COT), a atividade enzimática do solo pela taxa de hidrólise do diacetato de fluoresceína (FDA), o diâmetro médio ponderado de agregados estáveis em água (DMA) e a percentagem de macroagregados (PMA). O CBM e COT foram mais elevados na MN que nas áreas cultivadas, não diferindo, no entanto entre os três sistemas de manejo da cana-deaçúcar. A resposta de FDA aos manejos foi dependente da época de amostragem. No período chuvoso, os valores desta variável seguiram a ordem: MN > CO > CC > CQ; na época seca, apenas MN diferiu dos demais tratamentos. Independentemente da data de coleta, DMA e PMA decresceram na ordem MN > CO = CC > CQ. As variáveis DMA e PMA apresentaram sensibilidade satisfatória para diferenciar manejos de cana-deaçúcar e robustez à data de coleta. Após estes estudos foi analisada a distribuição da atividade enzimática medida pela hidrólise de FDA nas diferentes classes de agregados estáveis em água em amostras de solos de MN e cultivo de cana crua CC. Buscou-se com esta análise, averiguar o grau de associação entre o estado de agregação do solo e a atividade enzimática. Foi evidenciada a existência de uma compartimentalização diferenciada dos reservatórios de enzimas catalisadoras da hidrólise do FDA entre CC e MN. Observou-se uma relação não-monotônica entre estas duas variáveis. Para ambos os solos, classes de agregados intermediárias (0,25 a 1,00 mm) apresentaram menores valores de FDA que as classes abaixo e acima desta faixa de diâmetros.